Device Tree support for CMA (Contiguous Memory Allocator)

Add a function to scan the flattened device-tree starting from the node given by the path. It is used to extract information (like reserved memory), which is required on early boot before we can unflatten the tree.

Signed-off-by Marek Szyprowski <[email protected]>

Acked-by Michal Nazarewicz <[email protected]>

Acked-by Tomasz Figa <[email protected]>

Reviewed-by Rob Herring <[email protected]>

---
 drivers/of/fdt.c       |   76 ++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/of_fdt.h |    3 ++
 2 files changed, 79 insertions(+)

drivers/of/fdt.c +4 -0

index b10ba00..4fb06f3 100644
@@ -545,6 +545,82 @@ int __init of_flat_dt_match(unsigned long node, const char *const *compat)
 	return of_fdt_match(initial_boot_params, node, compat);
 }
 
+struct fdt_scan_status {
+	const char *name;
+	int namelen;
+	int depth;

drivers/of/fdt.c +17 -0

+{
+	struct fdt_scan_status *st = data;
+
+	/*
+	 * if scan at the requested fdt node has been completed,
+	 * return -ENXIO to abort further scanning
+	 */
+	if (depth <= st->depth)
+		return -ENXIO;
+
+	/* requested fdt node has been found, so call iterator function */
+	if (st->found)
+		return st->iterator(node, uname, depth, st->data);
+
+	/* check if scanning automata is entering next level of fdt nodes */
+	if (depth == st->depth + 1 &&
+	    strncmp(st->name, uname, st->namelen) == 0 &&

drivers/of/fdt.c +10 -0

+	}
+
+	/* scan next fdt node */
+	return 0;
+}
+
+/**
+ * of_scan_flat_dt_by_path - scan flattened tree blob and call callback on each
+ *			     child of the given path.
+ * @path: path to start searching for children

drivers/of/fdt.c +2 -0

+}
+
 #ifdef CONFIG_BLK_DEV_INITRD
 /**
  * early_init_dt_check_for_initrd - Decode initrd location from flat tree

include/linux/of_fdt.h +3 -0

index ed136ad..19f26f8 100644
@@ -90,6 +90,9 @@ extern void *of_get_flat_dt_prop(unsigned long node, const char *name,
 extern int of_flat_dt_is_compatible(unsigned long node, const char *name);
 extern int of_flat_dt_match(unsigned long node, const char *const *matches);
 extern unsigned long of_get_flat_dt_root(void);
+extern int of_scan_flat_dt_by_path(const char *path,
+	int (*it)(unsigned long node, const char *name, int depth, void *data),
+	void *data);
 
 extern int early_init_dt_scan_chosen(unsigned long node, const char *uname,
 				     int depth, void *data);

Signature · 1 line

1.7.9.5

Quoted 4 lines · Marek Szyprowski

Add a function to scan the flattened device-tree starting from the node given by the path. It is used to extract information (like reserved memory), which is required on early boot before we can unflatten the tree.

Quoted 4 lines

Signed-off-by Marek Szyprowski <[email protected]>

Acked-by Michal Nazarewicz <[email protected]>

Acked-by Tomasz Figa <[email protected]>

Reviewed-by Rob Herring <[email protected]>

Some nits below, but otherwise:

Acked-by Grant Likely <[email protected]>

I'm happy to take this through the DT tree, or have you take it via the CMA tree.

Quoted 17 lines

---
 drivers/of/fdt.c       |   76 ++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/of_fdt.h |    3 ++
 2 files changed, 79 insertions(+)

drivers/of/fdt.c +4 -0

index b10ba00..4fb06f3 100644
@@ -545,6 +545,82 @@ int __init of_flat_dt_match(unsigned long node, const char *const *compat)
 	return of_fdt_match(initial_boot_params, node, compat);
 }
 
+struct fdt_scan_status {
+	const char *name;
+	int namelen;
+	int depth;

drivers/of/fdt.c int __init of_flat_dt_match(unsigned long node, const char *const *compat) · line 561

Quoted 10 lines

drivers/of/fdt.c +10 -0

+	int found;
+	int (*iterator)(unsigned long node, const char *uname, int depth, void *data);
+	void *data;
+};
+
+/**
+ * fdt_scan_node_by_path - iterator for of_scan_flat_dt_by_path function
+ */
+static int __init fdt_scan_node_by_path(unsigned long node, const char *uname,
+					int depth, void *data)

Nit: since this is an iterator, I'd like to see "iter" in the function name.

Quoted 17 lines

drivers/of/fdt.c +17 -0

+{
+	struct fdt_scan_status *st = data;
+
+	/*
+	 * if scan at the requested fdt node has been completed,
+	 * return -ENXIO to abort further scanning
+	 */
+	if (depth <= st->depth)
+		return -ENXIO;
+
+	/* requested fdt node has been found, so call iterator function */
+	if (st->found)
+		return st->iterator(node, uname, depth, st->data);
+
+	/* check if scanning automata is entering next level of fdt nodes */
+	if (depth == st->depth + 1 &&
+	    strncmp(st->name, uname, st->namelen) == 0 &&

drivers/of/fdt.c int __init of_flat_dt_match(unsigned long node, const char *const *compat) · line 588

Quoted 10 lines

drivers/of/fdt.c +10 -0

+	    uname[st->namelen] == 0) {
+		st->depth += 1;
+		if (st->name[st->namelen] == 0) {
+			st->found = 1;
+		} else {
+			const char *next = st->name + st->namelen + 1;
+			st->name = next;
+			st->namelen = strcspn(next, "/");
+		}
+		return 0;

The above return statement is redundant.

Quoted 10 lines

drivers/of/fdt.c +10 -0

+	}
+
+	/* scan next fdt node */
+	return 0;
+}
+
+/**
+ * of_scan_flat_dt_by_path - scan flattened tree blob and call callback on each
+ *			     child of the given path.
+ * @path: path to start searching for children

drivers/of/fdt.c int __init of_flat_dt_match(unsigned long node, const char *const *compat) · line 608

Quoted 10 lines

drivers/of/fdt.c +10 -0

+ * @it: callback function
+ * @data: context data pointer
+ *
+ * This function is used to scan the flattened device-tree starting from the
+ * node given by path. It is used to extract information (like reserved
+ * memory), which is required on ealy boot before we can unflatten the tree.
+ */
+int __init of_scan_flat_dt_by_path(const char *path,
+	int (*it)(unsigned long node, const char *name, int depth, void *data),
+	void *data)

Nit: Please match the indentation convention used by of_scan_flat_dt(). This current version is really hard to read.

drivers/of/fdt.c int __init of_flat_dt_match(unsigned long node, const char *const *compat) · line 610

Quoted 2 lines

drivers/of/fdt.c +2 -0

+{
+	struct fdt_scan_status st = {path, 0, -1, 0, it, data};

This is a little fragile. If the structure gets modified, this line will break. I know it results in more text, but please use explicit data member assignments in initializers.

drivers/of/fdt.c int __init of_flat_dt_match(unsigned long node, const char *const *compat) · line 613

Quoted 3 lines

drivers/of/fdt.c +3 -0

+	int ret = 0;
+
+	if (initial_boot_params)

Nit:

	if (!initial_boot_params)
		return 0;

drivers/of/fdt.c int __init of_flat_dt_match(unsigned long node, const char *const *compat) · line 614

Quoted 1 line

drivers/of/fdt.c +1 -0

+                ret = of_scan_flat_dt(fdt_scan_node_by_path, &st);

Nit: inconsitent indentation (tabs vs. spaces)

drivers/of/fdt.c int __init of_flat_dt_match(unsigned long node, const char *const *compat) · line 621

Quoted 7 lines

drivers/of/fdt.c +7 -0

+
+	if (!st.found)
+		return -ENOENT;
+	else if (ret == -ENXIO)	/* scan has been completed */
+		return 0;
+	else
+		return ret;

Both uses of 'else' above are redundant. The only way the execution will pass that point is if it was the else case!

Quoted 17 lines

drivers/of/fdt.c +2 -0

+}
+
 #ifdef CONFIG_BLK_DEV_INITRD
 /**
  * early_init_dt_check_for_initrd - Decode initrd location from flat tree

include/linux/of_fdt.h +3 -0

index ed136ad..19f26f8 100644
@@ -90,6 +90,9 @@ extern void *of_get_flat_dt_prop(unsigned long node, const char *name,
 extern int of_flat_dt_is_compatible(unsigned long node, const char *name);
 extern int of_flat_dt_match(unsigned long node, const char *const *matches);
 extern unsigned long of_get_flat_dt_root(void);
+extern int of_scan_flat_dt_by_path(const char *path,
+	int (*it)(unsigned long node, const char *name, int depth, void *data),
+	void *data);
 

Quoted 5 lines

include/linux/of_fdt.h +0 -1

 extern int early_init_dt_scan_chosen(unsigned long node, const char *uname,
 				     int depth, void *data);
--

1.7.9.5

Hello,

Quoted 8 lines · Grant Likely

Quoted 5 lines · Marek Szyprowski

Add a function to scan the flattened device-tree starting from the node given by the path. It is used to extract information (like reserved memory), which is required on early boot before we can unflatten the tree.

Quoted 8 lines

Quoted 4 lines

Signed-off-by Marek Szyprowski <[email protected]>

Acked-by Michal Nazarewicz <[email protected]>

Acked-by Tomasz Figa <[email protected]>

Reviewed-by Rob Herring <[email protected]>

Some nits below, but otherwise:

Acked-by Grant Likely <[email protected]>

Thanks!

Quoted 2 lines

I'm happy to take this through the DT tree, or have you take it via the CMA tree.

I have already put the whole patchset in linux-next via my dma-mapping/cma tree,
so I would like to keep it there to avoid further confusion.

I only wonder how to handle the patches to get them merged to v3.12-rc1. After your review there will be some changes to the binding, its documentation
and the code itself. Would you mind if I send pull request with the current version and then provide incremental patches to fix the issues you have reported? Or should we delay this patchset till v3.13-rc1?

This patch adds device tree support for contiguous and reserved memory regions defined in device tree.

Large memory blocks can be reliably reserved only during early boot. This must happen before the whole memory management subsystem is initialized, because we need to ensure that the given contiguous blocks are not yet allocated by kernel. Also it must happen before kernel mappings for the whole low memory are created, to ensure that there will be no mappings (for reserved blocks) or mapping with special properties can be created (for CMA blocks). This all happens before device tree structures are unflattened, so we need to get reserved memory layout directly from fdt.

Later, those reserved memory regions are assigned to devices on each device structure initialization.

Signed-off-by Marek Szyprowski <[email protected]>

Acked-by Kyungmin Park <[email protected]>

Acked-by Michal Nazarewicz <[email protected]>

Acked-by Tomasz Figa <[email protected]>

Acked-by Stephen Warren <[email protected]>

Reviewed-by Rob Herring <[email protected]>

---
 Documentation/devicetree/bindings/memory.txt |  168 +++++++++++++++++++++++++
 drivers/of/Kconfig                           |    6 +
 drivers/of/Makefile                          |    1 +
 drivers/of/of_reserved_mem.c                 |  175 ++++++++++++++++++++++++++
 drivers/of/platform.c                        |    4 +
 include/linux/of_reserved_mem.h              |   14 +++
 6 files changed, 368 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/memory.txt
 create mode 100644 drivers/of/of_reserved_mem.c
 create mode 100644 include/linux/of_reserved_mem.h

Documentation/devicetree/bindings/memory.txt new file +42 -0

new file mode 100644
index 0000000..eb24693
@@ -0,0 +1,168 @@
+*** Memory binding ***
+
+The /memory node provides basic information about the address and size
+of the physical memory. This node is usually filled or updated by the
+bootloader, depending on the actual memory configuration of the given
+hardware.
+
+The memory layout is described by the following node:
+
+/ {
+	#address-cells = <(n)>;
+	#size-cells = <(m)>;
+	memory {
+		device_type = "memory";
+		reg =  <(baseaddr1) (size1)
+			(baseaddr2) (size2)
+			...
+			(baseaddrN) (sizeN)>;
+	};
+	...
+};
+
+A memory node follows the typical device tree rules for "reg" property:
+n:		number of cells used to store base address value
+m:		number of cells used to store size value
+baseaddrX:	defines a base address of the defined memory bank
+sizeX:		the size of the defined memory bank
+
+
+More than one memory bank can be defined.
+
+
+*** Reserved memory regions ***
+
+In /memory/reserved-memory node one can create child nodes describing
+particular reserved (excluded from normal use) memory regions. Such
+memory regions are usually designed for the special usage by various
+device drivers. A good example are contiguous memory allocations or
+memory sharing with other operating system on the same hardware board.
+Those special memory regions might depend on the board configuration and
+devices used on the target system.
+

Documentation/devicetree/bindings/memory.txt new file +11 -0

+/ {
+	#address-cells = <1>;
+	#size-cells = <1>;
+
+	/* ... */
+
+	memory {
+		reg =  <0x40000000 0x10000000
+			0x50000000 0x10000000
+			0x60000000 0x10000000
+			0x70000000 0x10000000>;

Documentation/devicetree/bindings/memory.txt new file +38 -0

+				linux,default-contiguous-region;
+			};
+
+			/*
+			 * special region for framebuffer
+			 */
+			display_region: region at 78000000 {
+				compatible = "linux,contiguous-memory-region", "reserved-memory-region";
+				reg = <0x78000000 0x800000>;
+			};
+
+			/*
+			 * special region for multimedia processing devices
+			 */
+			multimedia_region: region at 77000000 {
+				compatible = "linux,contiguous-memory-region";
+				reg = <0x77000000 0x4000000>;
+			};
+		};
+	};
+
+	/* ... */
+
+	fb0: fb at 12300000 {
+		status = "okay";
+		memory-region = <&display_region>;
+	};
+
+	scaler: scaler at 12500000 {
+		status = "okay";
+		memory-region = <&multimedia_region>;
+	};
+
+	codec: codec at 12600000 {
+		status = "okay";
+		memory-region = <&multimedia_region>;
+	};
+};

drivers/of/Kconfig +6 -0

index 80e5c13..f7107fa 100644
@@ -80,4 +80,10 @@ config OF_MTD
 	depends on MTD
 	def_bool y
 
+config OF_RESERVED_MEM
+	depends on DMA_CMA || (HAVE_GENERIC_DMA_COHERENT && HAVE_MEMBLOCK)
+	def_bool y
+	help
+	  Initialization code for DMA reserved memory
+
 endmenu # OF

drivers/of/Makefile +1 -0

index 1f9c0c4..e7e3322 100644
@@ -10,3 +10,4 @@ obj-$(CONFIG_OF_MDIO)	+= of_mdio.o
 obj-$(CONFIG_OF_PCI)	+= of_pci.o
 obj-$(CONFIG_OF_PCI_IRQ)  += of_pci_irq.o
 obj-$(CONFIG_OF_MTD)	+= of_mtd.o
+obj-$(CONFIG_OF_RESERVED_MEM) += of_reserved_mem.o

drivers/of/of_reserved_mem.c new file +18 -0

new file mode 100644
index 0000000..a754b84
@@ -0,0 +1,175 @@
+/*
+ * Device tree based initialization code for reserved memory.
+ *
+ * Copyright (c) 2013 Samsung Electronics Co., Ltd.
+ *		http://www.samsung.com
+ * Author: Marek Szyprowski <[email protected]>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License or (at your optional) any later version of the license.
+ */
+
+#include <asm/dma-contiguous.h>
+
+#include <linux/memblock.h>
+#include <linux/err.h>
+#include <linux/of.h>

drivers/of/of_reserved_mem.c new file +6 -0

+};
+static struct reserved_mem reserved_mem[MAX_RESERVED_REGIONS];
+static int reserved_mem_count;
+
+static int __init fdt_scan_reserved_mem(unsigned long node, const char *uname,
+					int depth, void *data)

drivers/of/of_reserved_mem.c new file +28 -0

+	is_reserved = of_flat_dt_is_compatible(node, "reserved-memory-region");
+
+	if (!is_reserved && !is_cma) {
+		/* ignore node and scan next one */
+		return 0;
+	}
+
+	status = of_get_flat_dt_prop(node, "status", &len);
+	if (status && strcmp(status, "okay") != 0) {
+		/* ignore disabled node nad scan next one */
+		return 0;
+	}
+
+	prop = of_get_flat_dt_prop(node, "reg", &len);
+	if (!prop || (len < (dt_root_size_cells + dt_root_addr_cells) *
+			     sizeof(__be32))) {
+		pr_err("Reserved mem: node %s, incorrect \"reg\" property\n",
+		       uname);
+		/* ignore node and scan next one */
+		return 0;
+	}
+	base = dt_mem_next_cell(dt_root_addr_cells, &prop);
+	size = dt_mem_next_cell(dt_root_size_cells, &prop);
+
+	if (!size) {
+		/* ignore node and scan next one */
+		return 0;
+	}

drivers/of/of_reserved_mem.c new file +88 -0

+
+	if (is_cma) {
+		struct cma *cma;
+		if (dma_contiguous_reserve_area(size, base, 0, &cma) == 0) {
+			rmem->cma = cma;
+			reserved_mem_count++;
+			if (of_get_flat_dt_prop(node,
+						"linux,default-contiguous-region",
+						NULL))
+				dma_contiguous_set_default(cma);
+		}
+	} else if (is_reserved) {
+		if (memblock_remove(base, size) == 0)
+			reserved_mem_count++;
+		else
+			pr_err("Failed to reserve memory for %s\n", uname);
+	}
+
+	return 0;
+}
+
+static struct reserved_mem *get_dma_memory_region(struct device *dev)
+{
+	struct device_node *node;
+	const char *name;
+	int i;
+
+	node = of_parse_phandle(dev->of_node, "memory-region", 0);
+	if (!node)
+		return NULL;
+
+	name = kbasename(node->full_name);
+	for (i = 0; i < reserved_mem_count; i++)
+		if (strcmp(name, reserved_mem[i].name) == 0)
+			return &reserved_mem[i];
+	return NULL;
+}
+
+/**
+ * of_reserved_mem_device_init() - assign reserved memory region to given device
+ *
+ * This function assign memory region pointed by "memory-region" device tree
+ * property to the given device.
+ */
+void of_reserved_mem_device_init(struct device *dev)
+{
+	struct reserved_mem *region = get_dma_memory_region(dev);
+	if (!region)
+		return;
+
+	if (region->cma) {
+		dev_set_cma_area(dev, region->cma);
+		pr_info("Assigned CMA %s to %s device\n", region->name,
+			dev_name(dev));
+	} else {
+		if (dma_declare_coherent_memory(dev, region->base, region->base,
+		    region->size, DMA_MEMORY_MAP | DMA_MEMORY_EXCLUSIVE) != 0)
+			pr_info("Declared reserved memory %s to %s device\n",
+				region->name, dev_name(dev));
+	}
+}
+
+/**
+ * of_reserved_mem_device_release() - release reserved memory device structures
+ *
+ * This function releases structures allocated for memory region handling for
+ * the given device.
+ */
+void of_reserved_mem_device_release(struct device *dev)
+{
+	struct reserved_mem *region = get_dma_memory_region(dev);
+	if (!region && !region->cma)
+		dma_release_declared_memory(dev);
+}
+
+/**
+ * early_init_dt_scan_reserved_mem() - create reserved memory regions
+ *
+ * This function grabs memory from early allocator for device exclusive use
+ * defined in device tree structures. It should be called by arch specific code
+ * once the early allocator (memblock) has been activated and all other
+ * subsystems have already allocated/reserved memory.
+ */
+void __init early_init_dt_scan_reserved_mem(void)
+{
+	of_scan_flat_dt_by_path("/memory/reserved-memory",
+				fdt_scan_reserved_mem, NULL);
+}

drivers/of/platform.c +4 -0

index e0a6514..eeca8a5 100644
@@ -21,6 +21,7 @@
 #include <linux/of_device.h>
 #include <linux/of_irq.h>
 #include <linux/of_platform.h>
+#include <linux/of_reserved_mem.h>
 #include <linux/platform_device.h>
 
 const struct of_device_id of_default_bus_match_table[] = {

@@ -218,6 +219,8 @@ struct platform_device *of_platform_device_create_pdata(
 	dev->dev.bus = &platform_bus_type;
 	dev->dev.platform_data = platform_data;
 
+	of_reserved_mem_device_init(&dev->dev);
+
 	/* We do not fill the DMA ops for platform devices by default.
 	 * This is currently the responsibility of the platform code
 	 * to do such, possibly using a device notifier

@@ -225,6 +228,7 @@ struct platform_device *of_platform_device_create_pdata(
 
 	if (of_device_add(dev) != 0) {
 		platform_device_put(dev);
+		of_reserved_mem_device_release(&dev->dev);
 		return NULL;
 	}
 

include/linux/of_reserved_mem.h new file +14 -0

new file mode 100644
index 0000000..c841282
@@ -0,0 +1,14 @@
+#ifndef __OF_RESERVED_MEM_H
+#define __OF_RESERVED_MEM_H
+
+#ifdef CONFIG_OF_RESERVED_MEM
+void of_reserved_mem_device_init(struct device *dev);
+void of_reserved_mem_device_release(struct device *dev);
+void early_init_dt_scan_reserved_mem(void);
+#else
+static inline void of_reserved_mem_device_init(struct device *dev) { }
+static inline void of_reserved_mem_device_release(struct device *dev) { }
+static inline void early_init_dt_scan_reserved_mem(void) { }
+#endif
+
+#endif /* __OF_RESERVED_MEM_H */

Signature · 1 line

1.7.9.5

Quoted 16 lines · Marek Szyprowski

This patch adds device tree support for contiguous and reserved memory regions defined in device tree.

Large memory blocks can be reliably reserved only during early boot. This must happen before the whole memory management subsystem is initialized, because we need to ensure that the given contiguous blocks are not yet allocated by kernel. Also it must happen before kernel mappings for the whole low memory are created, to ensure that there will be no mappings (for reserved blocks) or mapping with special properties can be created (for CMA blocks). This all happens before device tree structures are unflattened, so we need to get reserved memory layout directly from fdt.

Later, those reserved memory regions are assigned to devices on each device structure initialization.

Quoted 6 lines

Signed-off-by Marek Szyprowski <[email protected]>

Acked-by Kyungmin Park <[email protected]>

Acked-by Michal Nazarewicz <[email protected]>

Acked-by Tomasz Figa <[email protected]>

Acked-by Stephen Warren <[email protected]>

Reviewed-by Rob Herring <[email protected]>

Hi Marek,

This patch is in good shape, but I have some comments below and a few concerns about the binding....

g.

Quoted 66 lines

---
 Documentation/devicetree/bindings/memory.txt |  168 +++++++++++++++++++++++++
 drivers/of/Kconfig                           |    6 +
 drivers/of/Makefile                          |    1 +
 drivers/of/of_reserved_mem.c                 |  175 ++++++++++++++++++++++++++
 drivers/of/platform.c                        |    4 +
 include/linux/of_reserved_mem.h              |   14 +++
 6 files changed, 368 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/memory.txt
 create mode 100644 drivers/of/of_reserved_mem.c
 create mode 100644 include/linux/of_reserved_mem.h

Documentation/devicetree/bindings/memory.txt new file +48 -0

new file mode 100644
index 0000000..eb24693
@@ -0,0 +1,168 @@
+*** Memory binding ***
+
+The /memory node provides basic information about the address and size
+of the physical memory. This node is usually filled or updated by the
+bootloader, depending on the actual memory configuration of the given
+hardware.
+
+The memory layout is described by the following node:
+
+/ {
+	#address-cells = <(n)>;
+	#size-cells = <(m)>;
+	memory {
+		device_type = "memory";
+		reg =  <(baseaddr1) (size1)
+			(baseaddr2) (size2)
+			...
+			(baseaddrN) (sizeN)>;
+	};
+	...
+};
+
+A memory node follows the typical device tree rules for "reg" property:
+n:		number of cells used to store base address value
+m:		number of cells used to store size value
+baseaddrX:	defines a base address of the defined memory bank
+sizeX:		the size of the defined memory bank
+
+
+More than one memory bank can be defined.
+
+
+*** Reserved memory regions ***
+
+In /memory/reserved-memory node one can create child nodes describing
+particular reserved (excluded from normal use) memory regions. Such
+memory regions are usually designed for the special usage by various
+device drivers. A good example are contiguous memory allocations or
+memory sharing with other operating system on the same hardware board.
+Those special memory regions might depend on the board configuration and
+devices used on the target system.
+
+Parameters for each memory region can be encoded into the device tree
+with the following convention:
+
+[(label):] (name) {
+	compatible = "linux,contiguous-memory-region", "reserved-memory-region";
+	reg = <(address) (size)>;

Documentation/devicetree/bindings/memory.txt line 52

Quoted 4 lines

Documentation/devicetree/bindings/memory.txt new file +4 -0

+	(linux,default-contiguous-region);
+};
+
+compatible:	one or more of:

It's unclear what the meaning of having both values means for the kernel. Does it mean the regions is sharable with the kernel or not? I would think they are mutually exclusive.

Documentation/devicetree/bindings/memory.txt line 56

Quoted 4 lines

Documentation/devicetree/bindings/memory.txt new file +4 -0

+	- "linux,contiguous-memory-region" - enables binding of this
+	  region to Contiguous Memory Allocator (special region for
+	  contiguous memory allocations, shared with movable system
+	  memory, Linux kernel-specific).

As mentioned in the older thread, you can drop the 'linux,' prefix here. Perhaps something like "shareable-memory-region" or merely "memory-region". It is reasonable for any kernel (not just Linux) to use marked regions for movable pages until it gets requested by a driver, in which case a rather generic "memory-region" makes a lot of sense as a name.

Documentation/devicetree/bindings/memory.txt line 59

Quoted 3 lines

Documentation/devicetree/bindings/memory.txt new file +3 -0

+	- "reserved-memory-region" - compatibility is defined, given
+	  region is assigned for exclusive usage for by the respective
+	  devices.

BTW, just so you're aware there is already a binding for marking regions as reserved. It was recently added to arch/powerpc/kernel/prom.c. Unfortunately it doesn't look like it got documented. Search for "reserved-ranges". However, I don't think it blocks your work here. That binding doesn't provide any way for matching devices to reserved ranges. It is only for telling the kernel "hands of that memory".

Quoted 8 lines

Documentation/devicetree/bindings/memory.txt new file +8 -0

+
+reg:	standard property defining the base address and size of
+	the memory region
+
+linux,default-contiguous-region: property indicating that the region
+	is the default region for all contiguous memory
+	allocations, Linux specific (optional)
+

Documentation/devicetree/bindings/memory.txt line 70

Quoted 3 lines

Documentation/devicetree/bindings/memory.txt new file +3 -0

+It is optional to specify the base address, so if one wants to use
+autoconfiguration of the base address, '0' can be specified as a base
+address in the 'reg' property.

I don't understand this. What does autoconfiguration of the base address actually do? If this is intended to dynamically allocate a region of RAM for contiguous allocations, then don't use 'reg'. Use a different property that only specifies the size.

Documentation/devicetree/bindings/memory.txt line 73

Quoted 2 lines

Documentation/devicetree/bindings/memory.txt new file +2 -0

+The /memory/reserved-memory node must contain the same #address-cells
+and #size-cells value as the root node.

That seems to be an arbitrary restriction. Why does the reserved-memory node need to have exactly the same #address/size values? The 'reg' property binding quite easily handles different values at different levels of the tree. More below....

Quoted 11 lines

Documentation/devicetree/bindings/memory.txt new file +11 -0

+/ {
+	#address-cells = <1>;
+	#size-cells = <1>;
+
+	/* ... */
+
+	memory {
+		reg =  <0x40000000 0x10000000
+			0x50000000 0x10000000
+			0x60000000 0x10000000
+			0x70000000 0x10000000>;

Documentation/devicetree/bindings/memory.txt line 128

Quoted 10 lines

Documentation/devicetree/bindings/memory.txt new file +10 -0

+
+		reserved-memory {
+			#address-cells = <1>;
+			#size-cells = <1>;
+
+			/*
+			 * global autoconfigured region for contiguous allocations
+			 * (used only with Contiguous Memory Allocator)
+			 */
+			contig_region at 0 {

I would expect this to be "region at 0", not "contig_region". Also, the '_' character is strongly discouraged in node names.

Documentation/devicetree/bindings/memory.txt line 130

Quoted 2 lines

Documentation/devicetree/bindings/memory.txt new file +2 -0

+				compatible = "linux,contiguous-memory-region";
+				reg = <0x0 0x4000000>;

As written, this example tree is abusing the 'reg' binding. Whenever a node has a mappable 'reg' propertie, then all of the parent nodes above it need to have 'ranges' properties. In this case it is pretty easy to fix by simply adding "ranges;" to the reserved-memory and memory nodes. An empty ranges property simply means that all addresses are 1:1 mapped if #address/size are the same between each parent/child.

The documentation above should specify that both memory and reserved-memory need to have 'ranges', but can suggest that the best use-case is for ranges to be empty.

I mentioned above that #address/#size can actually be different. If someone wants to do that, then they need to have a fully specified ranges property that declares the mapping from one address space to another.

I'm okay with the implementation as it currently stands, but only if you make it test for the presence of an empty ranges property. If ranges is missing, or if it has data in it then it should throw an error that it cannot be parsed.

Quoted 86 lines

Documentation/devicetree/bindings/memory.txt new file +38 -0

+				linux,default-contiguous-region;
+			};
+
+			/*
+			 * special region for framebuffer
+			 */
+			display_region: region at 78000000 {
+				compatible = "linux,contiguous-memory-region", "reserved-memory-region";
+				reg = <0x78000000 0x800000>;
+			};
+
+			/*
+			 * special region for multimedia processing devices
+			 */
+			multimedia_region: region at 77000000 {
+				compatible = "linux,contiguous-memory-region";
+				reg = <0x77000000 0x4000000>;
+			};
+		};
+	};
+
+	/* ... */
+
+	fb0: fb at 12300000 {
+		status = "okay";
+		memory-region = <&display_region>;
+	};
+
+	scaler: scaler at 12500000 {
+		status = "okay";
+		memory-region = <&multimedia_region>;
+	};
+
+	codec: codec at 12600000 {
+		status = "okay";
+		memory-region = <&multimedia_region>;
+	};
+};

drivers/of/Kconfig +6 -0

index 80e5c13..f7107fa 100644
@@ -80,4 +80,10 @@ config OF_MTD
 	depends on MTD
 	def_bool y
 
+config OF_RESERVED_MEM
+	depends on DMA_CMA || (HAVE_GENERIC_DMA_COHERENT && HAVE_MEMBLOCK)
+	def_bool y
+	help
+	  Initialization code for DMA reserved memory
+
 endmenu # OF

drivers/of/Makefile +1 -0

index 1f9c0c4..e7e3322 100644
@@ -10,3 +10,4 @@ obj-$(CONFIG_OF_MDIO)	+= of_mdio.o
 obj-$(CONFIG_OF_PCI)	+= of_pci.o
 obj-$(CONFIG_OF_PCI_IRQ)  += of_pci_irq.o
 obj-$(CONFIG_OF_MTD)	+= of_mtd.o
+obj-$(CONFIG_OF_RESERVED_MEM) += of_reserved_mem.o

drivers/of/of_reserved_mem.c new file +18 -0

new file mode 100644
index 0000000..a754b84
@@ -0,0 +1,175 @@
+/*
+ * Device tree based initialization code for reserved memory.
+ *
+ * Copyright (c) 2013 Samsung Electronics Co., Ltd.
+ *		http://www.samsung.com
+ * Author: Marek Szyprowski <[email protected]>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License or (at your optional) any later version of the license.
+ */
+
+#include <asm/dma-contiguous.h>
+
+#include <linux/memblock.h>
+#include <linux/err.h>
+#include <linux/of.h>

drivers/of/of_reserved_mem.c line 28

Quoted 10 lines

drivers/of/of_reserved_mem.c new file +10 -0

+#include <linux/of_fdt.h>
+#include <linux/of_platform.h>
+#include <linux/mm.h>
+#include <linux/sizes.h>
+#include <linux/mm_types.h>
+#include <linux/dma-contiguous.h>
+#include <linux/dma-mapping.h>
+#include <linux/of_reserved_mem.h>
+
+#define MAX_RESERVED_REGIONS	16

Nit: This seems a little arbitrary. I would expect the reserved_mem array to be dynamically allocated. I'm not going to force you to change this, but it should be revisited with a follow-on patch.

drivers/of/of_reserved_mem.c line 33

Quoted 5 lines

drivers/of/of_reserved_mem.c new file +5 -0

+struct reserved_mem {
+	phys_addr_t		base;
+	unsigned long		size;
+	struct cma		*cma;
+	char			name[32];

Why is name a fixed size string? And why is it a magic size of 32?

Quoted 6 lines

drivers/of/of_reserved_mem.c new file +6 -0

+};
+static struct reserved_mem reserved_mem[MAX_RESERVED_REGIONS];
+static int reserved_mem_count;
+
+static int __init fdt_scan_reserved_mem(unsigned long node, const char *uname,
+					int depth, void *data)

drivers/of/of_reserved_mem.c line 49

Quoted 10 lines

drivers/of/of_reserved_mem.c new file +10 -0

+{
+	struct reserved_mem *rmem = &reserved_mem[reserved_mem_count];
+	phys_addr_t base, size;
+	int is_cma, is_reserved;
+	unsigned long len;
+	const char *status;
+	__be32 *prop;
+
+	is_cma = IS_ENABLED(CONFIG_DMA_CMA) &&
+	       of_flat_dt_is_compatible(node, "linux,contiguous-memory-region");

Nit: Indentation by tabs.

Quoted 34 lines

drivers/of/of_reserved_mem.c new file +34 -0

+	is_reserved = of_flat_dt_is_compatible(node, "reserved-memory-region");
+
+	if (!is_reserved && !is_cma) {
+		/* ignore node and scan next one */
+		return 0;
+	}
+
+	status = of_get_flat_dt_prop(node, "status", &len);
+	if (status && strcmp(status, "okay") != 0) {
+		/* ignore disabled node nad scan next one */
+		return 0;
+	}
+
+	prop = of_get_flat_dt_prop(node, "reg", &len);
+	if (!prop || (len < (dt_root_size_cells + dt_root_addr_cells) *
+			     sizeof(__be32))) {
+		pr_err("Reserved mem: node %s, incorrect \"reg\" property\n",
+		       uname);
+		/* ignore node and scan next one */
+		return 0;
+	}
+	base = dt_mem_next_cell(dt_root_addr_cells, &prop);
+	size = dt_mem_next_cell(dt_root_size_cells, &prop);
+
+	if (!size) {
+		/* ignore node and scan next one */
+		return 0;
+	}
+
+	pr_info("Reserved mem: found %s, memory base %lx, size %ld MiB\n",
+		uname, (unsigned long)base, (unsigned long)size / SZ_1M);
+
+	if (reserved_mem_count == ARRAY_SIZE(reserved_mem))
+		return -ENOSPC;

drivers/of/of_reserved_mem.c line 87

Quoted 4 lines

drivers/of/of_reserved_mem.c new file +4 -0

+
+	rmem->base = base;
+	rmem->size = size;
+	strlcpy(rmem->name, uname, sizeof(rmem->name));

If I'm reading the code correctly, uname is directly from the flattened device tree and is safe to keep a pointer to. Can you make rmem->name a char* and merely do a rmem->name = uname;?

Quoted 131 lines

drivers/of/of_reserved_mem.c new file +88 -0

+
+	if (is_cma) {
+		struct cma *cma;
+		if (dma_contiguous_reserve_area(size, base, 0, &cma) == 0) {
+			rmem->cma = cma;
+			reserved_mem_count++;
+			if (of_get_flat_dt_prop(node,
+						"linux,default-contiguous-region",
+						NULL))
+				dma_contiguous_set_default(cma);
+		}
+	} else if (is_reserved) {
+		if (memblock_remove(base, size) == 0)
+			reserved_mem_count++;
+		else
+			pr_err("Failed to reserve memory for %s\n", uname);
+	}
+
+	return 0;
+}
+
+static struct reserved_mem *get_dma_memory_region(struct device *dev)
+{
+	struct device_node *node;
+	const char *name;
+	int i;
+
+	node = of_parse_phandle(dev->of_node, "memory-region", 0);
+	if (!node)
+		return NULL;
+
+	name = kbasename(node->full_name);
+	for (i = 0; i < reserved_mem_count; i++)
+		if (strcmp(name, reserved_mem[i].name) == 0)
+			return &reserved_mem[i];
+	return NULL;
+}
+
+/**
+ * of_reserved_mem_device_init() - assign reserved memory region to given device
+ *
+ * This function assign memory region pointed by "memory-region" device tree
+ * property to the given device.
+ */
+void of_reserved_mem_device_init(struct device *dev)
+{
+	struct reserved_mem *region = get_dma_memory_region(dev);
+	if (!region)
+		return;
+
+	if (region->cma) {
+		dev_set_cma_area(dev, region->cma);
+		pr_info("Assigned CMA %s to %s device\n", region->name,
+			dev_name(dev));
+	} else {
+		if (dma_declare_coherent_memory(dev, region->base, region->base,
+		    region->size, DMA_MEMORY_MAP | DMA_MEMORY_EXCLUSIVE) != 0)
+			pr_info("Declared reserved memory %s to %s device\n",
+				region->name, dev_name(dev));
+	}
+}
+
+/**
+ * of_reserved_mem_device_release() - release reserved memory device structures
+ *
+ * This function releases structures allocated for memory region handling for
+ * the given device.
+ */
+void of_reserved_mem_device_release(struct device *dev)
+{
+	struct reserved_mem *region = get_dma_memory_region(dev);
+	if (!region && !region->cma)
+		dma_release_declared_memory(dev);
+}
+
+/**
+ * early_init_dt_scan_reserved_mem() - create reserved memory regions
+ *
+ * This function grabs memory from early allocator for device exclusive use
+ * defined in device tree structures. It should be called by arch specific code
+ * once the early allocator (memblock) has been activated and all other
+ * subsystems have already allocated/reserved memory.
+ */
+void __init early_init_dt_scan_reserved_mem(void)
+{
+	of_scan_flat_dt_by_path("/memory/reserved-memory",
+				fdt_scan_reserved_mem, NULL);
+}

drivers/of/platform.c +4 -0

index e0a6514..eeca8a5 100644
@@ -21,6 +21,7 @@
 #include <linux/of_device.h>
 #include <linux/of_irq.h>
 #include <linux/of_platform.h>
+#include <linux/of_reserved_mem.h>
 #include <linux/platform_device.h>
 
 const struct of_device_id of_default_bus_match_table[] = {

@@ -218,6 +219,8 @@ struct platform_device *of_platform_device_create_pdata(
 	dev->dev.bus = &platform_bus_type;
 	dev->dev.platform_data = platform_data;
 
+	of_reserved_mem_device_init(&dev->dev);
+
 	/* We do not fill the DMA ops for platform devices by default.
 	 * This is currently the responsibility of the platform code
 	 * to do such, possibly using a device notifier

@@ -225,6 +228,7 @@ struct platform_device *of_platform_device_create_pdata(
 
 	if (of_device_add(dev) != 0) {
 		platform_device_put(dev);
+		of_reserved_mem_device_release(&dev->dev);
 		return NULL;
 	}
 

include/linux/of_reserved_mem.h new file +8 -0

new file mode 100644
index 0000000..c841282
@@ -0,0 +1,14 @@
+#ifndef __OF_RESERVED_MEM_H
+#define __OF_RESERVED_MEM_H
+
+#ifdef CONFIG_OF_RESERVED_MEM
+void of_reserved_mem_device_init(struct device *dev);
+void of_reserved_mem_device_release(struct device *dev);
+void early_init_dt_scan_reserved_mem(void);
+#else

Quoted 8 lines

include/linux/of_reserved_mem.h new file +6 -1

+static inline void of_reserved_mem_device_init(struct device *dev) { }
+static inline void of_reserved_mem_device_release(struct device *dev) { }
+static inline void early_init_dt_scan_reserved_mem(void) { }
+#endif
+
+#endif /* __OF_RESERVED_MEM_H */
--

1.7.9.5

Hello,

Quoted 97 lines · Grant Likely

Quoted 16 lines · Marek Szyprowski

This patch adds device tree support for contiguous and reserved memory regions defined in device tree.

Large memory blocks can be reliably reserved only during early boot. This must happen before the whole memory management subsystem is initialized, because we need to ensure that the given contiguous blocks are not yet allocated by kernel. Also it must happen before kernel mappings for the whole low memory are created, to ensure that there will be no mappings (for reserved blocks) or mapping with special properties can be created (for CMA blocks). This all happens before device tree structures are unflattened, so we need to get reserved memory layout directly from fdt.

Later, those reserved memory regions are assigned to devices on each device structure initialization.

Quoted 6 lines

Signed-off-by Marek Szyprowski <[email protected]>

Acked-by Kyungmin Park <[email protected]>

Acked-by Michal Nazarewicz <[email protected]>

Acked-by Tomasz Figa <[email protected]>

Acked-by Stephen Warren <[email protected]>

Reviewed-by Rob Herring <[email protected]>

Hi Marek,

This patch is in good shape, but I have some comments below and a few concerns about the binding....

g.

Quoted 66 lines

---
 Documentation/devicetree/bindings/memory.txt |  168 +++++++++++++++++++++++++
 drivers/of/Kconfig                           |    6 +
 drivers/of/Makefile                          |    1 +
 drivers/of/of_reserved_mem.c                 |  175 ++++++++++++++++++++++++++
 drivers/of/platform.c                        |    4 +
 include/linux/of_reserved_mem.h              |   14 +++
 6 files changed, 368 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/memory.txt
 create mode 100644 drivers/of/of_reserved_mem.c
 create mode 100644 include/linux/of_reserved_mem.h

Documentation/devicetree/bindings/memory.txt new file +48 -0

new file mode 100644
index 0000000..eb24693
@@ -0,0 +1,168 @@
+*** Memory binding ***
+
+The /memory node provides basic information about the address and size
+of the physical memory. This node is usually filled or updated by the
+bootloader, depending on the actual memory configuration of the given
+hardware.
+
+The memory layout is described by the following node:
+
+/ {
+	#address-cells = <(n)>;
+	#size-cells = <(m)>;
+	memory {
+		device_type = "memory";
+		reg =  <(baseaddr1) (size1)
+			(baseaddr2) (size2)
+			...
+			(baseaddrN) (sizeN)>;
+	};
+	...
+};
+
+A memory node follows the typical device tree rules for "reg" property:
+n:		number of cells used to store base address value
+m:		number of cells used to store size value
+baseaddrX:	defines a base address of the defined memory bank
+sizeX:		the size of the defined memory bank
+
+
+More than one memory bank can be defined.
+
+
+*** Reserved memory regions ***
+
+In /memory/reserved-memory node one can create child nodes describing
+particular reserved (excluded from normal use) memory regions. Such
+memory regions are usually designed for the special usage by various
+device drivers. A good example are contiguous memory allocations or
+memory sharing with other operating system on the same hardware board.
+Those special memory regions might depend on the board configuration and
+devices used on the target system.
+
+Parameters for each memory region can be encoded into the device tree
+with the following convention:
+
+[(label):] (name) {
+	compatible = "linux,contiguous-memory-region", "reserved-memory-region";
+	reg = <(address) (size)>;

Quoted 8 lines

Documentation/devicetree/bindings/memory.txt line 52

Quoted 4 lines

Documentation/devicetree/bindings/memory.txt new file +4 -0

+	(linux,default-contiguous-region);
+};
+
+compatible:	one or more of:

It's unclear what the meaning of having both values means for the kernel. Does it mean the regions is sharable with the kernel or not? I would think they are mutually exclusive.

I consider CMA ("linux,contiguous-memory-region") as a special case of the reserved memory driver. The main advantage is the ability of sharing the memory with the system instead of just allocating it from the carved out memory region. From the device and hardware perspective there is no difference if the buffer comes from CMA or reserved memory. However if you insist, I can change it to something different, like "shareable-memory-region".

Specifying both compatible values would let kernel to bind the more specific driver (cma, if available) over the generic one (simple reserved memory carve-out allocator based on dma_coherent).

Quoted 12 lines

Documentation/devicetree/bindings/memory.txt line 56

Quoted 4 lines

Documentation/devicetree/bindings/memory.txt new file +4 -0

+	- "linux,contiguous-memory-region" - enables binding of this
+	  region to Contiguous Memory Allocator (special region for
+	  contiguous memory allocations, shared with movable system
+	  memory, Linux kernel-specific).

As mentioned in the older thread, you can drop the 'linux,' prefix here. Perhaps something like "shareable-memory-region" or merely "memory-region". It is reasonable for any kernel (not just Linux) to use marked regions for movable pages until it gets requested by a driver, in which case a rather generic "memory-region" makes a lot of sense as a name.

Quoted 10 lines

Documentation/devicetree/bindings/memory.txt line 59

Quoted 3 lines

Documentation/devicetree/bindings/memory.txt new file +3 -0

+	- "reserved-memory-region" - compatibility is defined, given
+	  region is assigned for exclusive usage for by the respective
+	  devices.

BTW, just so you're aware there is already a binding for marking regions as reserved. It was recently added to arch/powerpc/kernel/prom.c. Unfortunately it doesn't look like it got documented. Search for "reserved-ranges". However, I don't think it blocks your work here. That binding doesn't provide any way for matching devices to reserved ranges. It is only for telling the kernel "hands of that memory".

ok, good to know.

Quoted 8 lines

Quoted 8 lines

Documentation/devicetree/bindings/memory.txt new file +8 -0

+
+reg:	standard property defining the base address and size of
+	the memory region
+
+linux,default-contiguous-region: property indicating that the region
+	is the default region for all contiguous memory
+	allocations, Linux specific (optional)
+

Quoted 8 lines

Documentation/devicetree/bindings/memory.txt line 70

Quoted 3 lines

Documentation/devicetree/bindings/memory.txt new file +3 -0

+It is optional to specify the base address, so if one wants to use
+autoconfiguration of the base address, '0' can be specified as a base
+address in the 'reg' property.

I don't understand this. What does autoconfiguration of the base address actually do? If this is intended to dynamically allocate a region of RAM for contiguous allocations, then don't use 'reg'. Use a different property that only specifies the size.

Ok, I will try to make a patch which removes special 'zero' base address handling and adds separate 'size' property for automatically configured regions.

Quoted 7 lines

Documentation/devicetree/bindings/memory.txt line 73

Quoted 2 lines

Documentation/devicetree/bindings/memory.txt new file +2 -0

+The /memory/reserved-memory node must contain the same #address-cells
+and #size-cells value as the root node.

That seems to be an arbitrary restriction. Why does the reserved-memory node need to have exactly the same #address/size values? The 'reg' property binding quite easily handles different values at different levels of the tree. More below....

Does it really makes sense to have such configuration with different #address-cells/#size-cells than the root memory node?

Quoted 44 lines

Quoted 11 lines

Documentation/devicetree/bindings/memory.txt new file +11 -0

+/ {
+	#address-cells = <1>;
+	#size-cells = <1>;
+
+	/* ... */
+
+	memory {
+		reg =  <0x40000000 0x10000000
+			0x50000000 0x10000000
+			0x60000000 0x10000000
+			0x70000000 0x10000000>;

Documentation/devicetree/bindings/memory.txt line 128

Quoted 10 lines

Documentation/devicetree/bindings/memory.txt new file +10 -0

+
+		reserved-memory {
+			#address-cells = <1>;
+			#size-cells = <1>;
+
+			/*
+			 * global autoconfigured region for contiguous allocations
+			 * (used only with Contiguous Memory Allocator)
+			 */
+			contig_region at 0 {

I would expect this to be "region at 0", not "contig_region". Also, the '_' character is strongly discouraged in node names.

Documentation/devicetree/bindings/memory.txt line 130

Quoted 2 lines

Documentation/devicetree/bindings/memory.txt new file +2 -0

+				compatible = "linux,contiguous-memory-region";
+				reg = <0x0 0x4000000>;

As written, this example tree is abusing the 'reg' binding. Whenever a node has a mappable 'reg' propertie, then all of the parent nodes above it need to have 'ranges' properties. In this case it is pretty easy to fix by simply adding "ranges;" to the reserved-memory and memory nodes. An empty ranges property simply means that all addresses are 1:1 mapped if #address/size are the same between each parent/child.

The documentation above should specify that both memory and reserved-memory need to have 'ranges', but can suggest that the best use-case is for ranges to be empty.

I mentioned above that #address/#size can actually be different. If someone wants to do that, then they need to have a fully specified ranges property that declares the mapping from one address space to another.

Quoted 4 lines

I'm okay with the implementation as it currently stands, but only if you make it test for the presence of an empty ranges property. If ranges is missing, or if it has data in it then it should throw an error that it cannot be parsed.

Ok, now I see the problem. Too bad that the ranges and #address/#size cells need to be parsed from FDT, what makes the code much more complicated, especially because there is almost no infrastructure for parsing it. I can resurrect the simple code for parsing FDT from V5 of the patches (see
http://thread.gmane.org/gmane.linux.ports.arm.kernel/259278/focus=259281 ), but Rob already pointed that such code is quite hard to understand.

Quoted 162 lines

Quoted 86 lines

Documentation/devicetree/bindings/memory.txt new file +38 -0

+				linux,default-contiguous-region;
+			};
+
+			/*
+			 * special region for framebuffer
+			 */
+			display_region: region at 78000000 {
+				compatible = "linux,contiguous-memory-region", "reserved-memory-region";
+				reg = <0x78000000 0x800000>;
+			};
+
+			/*
+			 * special region for multimedia processing devices
+			 */
+			multimedia_region: region at 77000000 {
+				compatible = "linux,contiguous-memory-region";
+				reg = <0x77000000 0x4000000>;
+			};
+		};
+	};
+
+	/* ... */
+
+	fb0: fb at 12300000 {
+		status = "okay";
+		memory-region = <&display_region>;
+	};
+
+	scaler: scaler at 12500000 {
+		status = "okay";
+		memory-region = <&multimedia_region>;
+	};
+
+	codec: codec at 12600000 {
+		status = "okay";
+		memory-region = <&multimedia_region>;
+	};
+};

drivers/of/Kconfig +6 -0

index 80e5c13..f7107fa 100644
@@ -80,4 +80,10 @@ config OF_MTD
 	depends on MTD
 	def_bool y
 
+config OF_RESERVED_MEM
+	depends on DMA_CMA || (HAVE_GENERIC_DMA_COHERENT && HAVE_MEMBLOCK)
+	def_bool y
+	help
+	  Initialization code for DMA reserved memory
+
 endmenu # OF

drivers/of/Makefile +1 -0

index 1f9c0c4..e7e3322 100644
@@ -10,3 +10,4 @@ obj-$(CONFIG_OF_MDIO)	+= of_mdio.o
 obj-$(CONFIG_OF_PCI)	+= of_pci.o
 obj-$(CONFIG_OF_PCI_IRQ)  += of_pci_irq.o
 obj-$(CONFIG_OF_MTD)	+= of_mtd.o
+obj-$(CONFIG_OF_RESERVED_MEM) += of_reserved_mem.o

drivers/of/of_reserved_mem.c new file +18 -0

new file mode 100644
index 0000000..a754b84
@@ -0,0 +1,175 @@
+/*
+ * Device tree based initialization code for reserved memory.
+ *
+ * Copyright (c) 2013 Samsung Electronics Co., Ltd.
+ *		http://www.samsung.com
+ * Author: Marek Szyprowski <[email protected]>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License or (at your optional) any later version of the license.
+ */
+
+#include <asm/dma-contiguous.h>
+
+#include <linux/memblock.h>
+#include <linux/err.h>
+#include <linux/of.h>

drivers/of/of_reserved_mem.c line 28

Quoted 10 lines

drivers/of/of_reserved_mem.c new file +10 -0

+#include <linux/of_fdt.h>
+#include <linux/of_platform.h>
+#include <linux/mm.h>
+#include <linux/sizes.h>
+#include <linux/mm_types.h>
+#include <linux/dma-contiguous.h>
+#include <linux/dma-mapping.h>
+#include <linux/of_reserved_mem.h>
+
+#define MAX_RESERVED_REGIONS	16

Nit: This seems a little arbitrary. I would expect the reserved_mem array to be dynamically allocated. I'm not going to force you to change this, but it should be revisited with a follow-on patch.

drivers/of/of_reserved_mem.c line 33

Quoted 5 lines

drivers/of/of_reserved_mem.c new file +5 -0

+struct reserved_mem {
+	phys_addr_t		base;
+	unsigned long		size;
+	struct cma		*cma;
+	char			name[32];

Why is name a fixed size string? And why is it a magic size of 32?

Quoted 6 lines

drivers/of/of_reserved_mem.c new file +6 -0

+};
+static struct reserved_mem reserved_mem[MAX_RESERVED_REGIONS];
+static int reserved_mem_count;
+
+static int __init fdt_scan_reserved_mem(unsigned long node, const char *uname,
+					int depth, void *data)

drivers/of/of_reserved_mem.c line 49

Quoted 10 lines

drivers/of/of_reserved_mem.c new file +10 -0

+{
+	struct reserved_mem *rmem = &reserved_mem[reserved_mem_count];
+	phys_addr_t base, size;
+	int is_cma, is_reserved;
+	unsigned long len;
+	const char *status;
+	__be32 *prop;
+
+	is_cma = IS_ENABLED(CONFIG_DMA_CMA) &&
+	       of_flat_dt_is_compatible(node, "linux,contiguous-memory-region");

Nit: Indentation by tabs.

Quoted 34 lines

drivers/of/of_reserved_mem.c new file +34 -0

+	is_reserved = of_flat_dt_is_compatible(node, "reserved-memory-region");
+
+	if (!is_reserved && !is_cma) {
+		/* ignore node and scan next one */
+		return 0;
+	}
+
+	status = of_get_flat_dt_prop(node, "status", &len);
+	if (status && strcmp(status, "okay") != 0) {
+		/* ignore disabled node nad scan next one */
+		return 0;
+	}
+
+	prop = of_get_flat_dt_prop(node, "reg", &len);
+	if (!prop || (len < (dt_root_size_cells + dt_root_addr_cells) *
+			     sizeof(__be32))) {
+		pr_err("Reserved mem: node %s, incorrect \"reg\" property\n",
+		       uname);
+		/* ignore node and scan next one */
+		return 0;
+	}
+	base = dt_mem_next_cell(dt_root_addr_cells, &prop);
+	size = dt_mem_next_cell(dt_root_size_cells, &prop);
+
+	if (!size) {
+		/* ignore node and scan next one */
+		return 0;
+	}
+
+	pr_info("Reserved mem: found %s, memory base %lx, size %ld MiB\n",
+		uname, (unsigned long)base, (unsigned long)size / SZ_1M);
+
+	if (reserved_mem_count == ARRAY_SIZE(reserved_mem))
+		return -ENOSPC;

Quoted 8 lines

drivers/of/of_reserved_mem.c line 87

Quoted 4 lines

drivers/of/of_reserved_mem.c new file +4 -0

+
+	rmem->base = base;
+	rmem->size = size;
+	strlcpy(rmem->name, uname, sizeof(rmem->name));

If I'm reading the code correctly, uname is directly from the flattened device tree and is safe to keep a pointer to. Can you make rmem->name a char* and merely do a rmem->name = uname;?

Ok, I didn't know it is safe to keep a pointer to FDT.

Quoted 131 lines

Quoted 131 lines

drivers/of/of_reserved_mem.c new file +88 -0

+
+	if (is_cma) {
+		struct cma *cma;
+		if (dma_contiguous_reserve_area(size, base, 0, &cma) == 0) {
+			rmem->cma = cma;
+			reserved_mem_count++;
+			if (of_get_flat_dt_prop(node,
+						"linux,default-contiguous-region",
+						NULL))
+				dma_contiguous_set_default(cma);
+		}
+	} else if (is_reserved) {
+		if (memblock_remove(base, size) == 0)
+			reserved_mem_count++;
+		else
+			pr_err("Failed to reserve memory for %s\n", uname);
+	}
+
+	return 0;
+}
+
+static struct reserved_mem *get_dma_memory_region(struct device *dev)
+{
+	struct device_node *node;
+	const char *name;
+	int i;
+
+	node = of_parse_phandle(dev->of_node, "memory-region", 0);
+	if (!node)
+		return NULL;
+
+	name = kbasename(node->full_name);
+	for (i = 0; i < reserved_mem_count; i++)
+		if (strcmp(name, reserved_mem[i].name) == 0)
+			return &reserved_mem[i];
+	return NULL;
+}
+
+/**
+ * of_reserved_mem_device_init() - assign reserved memory region to given device
+ *
+ * This function assign memory region pointed by "memory-region" device tree
+ * property to the given device.
+ */
+void of_reserved_mem_device_init(struct device *dev)
+{
+	struct reserved_mem *region = get_dma_memory_region(dev);
+	if (!region)
+		return;
+
+	if (region->cma) {
+		dev_set_cma_area(dev, region->cma);
+		pr_info("Assigned CMA %s to %s device\n", region->name,
+			dev_name(dev));
+	} else {
+		if (dma_declare_coherent_memory(dev, region->base, region->base,
+		    region->size, DMA_MEMORY_MAP | DMA_MEMORY_EXCLUSIVE) != 0)
+			pr_info("Declared reserved memory %s to %s device\n",
+				region->name, dev_name(dev));
+	}
+}
+
+/**
+ * of_reserved_mem_device_release() - release reserved memory device structures
+ *
+ * This function releases structures allocated for memory region handling for
+ * the given device.
+ */
+void of_reserved_mem_device_release(struct device *dev)
+{
+	struct reserved_mem *region = get_dma_memory_region(dev);
+	if (!region && !region->cma)
+		dma_release_declared_memory(dev);
+}
+
+/**
+ * early_init_dt_scan_reserved_mem() - create reserved memory regions
+ *
+ * This function grabs memory from early allocator for device exclusive use
+ * defined in device tree structures. It should be called by arch specific code
+ * once the early allocator (memblock) has been activated and all other
+ * subsystems have already allocated/reserved memory.
+ */
+void __init early_init_dt_scan_reserved_mem(void)
+{
+	of_scan_flat_dt_by_path("/memory/reserved-memory",
+				fdt_scan_reserved_mem, NULL);
+}

drivers/of/platform.c +4 -0

index e0a6514..eeca8a5 100644
@@ -21,6 +21,7 @@
 #include <linux/of_device.h>
 #include <linux/of_irq.h>
 #include <linux/of_platform.h>
+#include <linux/of_reserved_mem.h>
 #include <linux/platform_device.h>
 
 const struct of_device_id of_default_bus_match_table[] = {

@@ -218,6 +219,8 @@ struct platform_device *of_platform_device_create_pdata(
 	dev->dev.bus = &platform_bus_type;
 	dev->dev.platform_data = platform_data;
 
+	of_reserved_mem_device_init(&dev->dev);
+
 	/* We do not fill the DMA ops for platform devices by default.
 	 * This is currently the responsibility of the platform code
 	 * to do such, possibly using a device notifier

@@ -225,6 +228,7 @@ struct platform_device *of_platform_device_create_pdata(
 
 	if (of_device_add(dev) != 0) {
 		platform_device_put(dev);
+		of_reserved_mem_device_release(&dev->dev);
 		return NULL;
 	}
 

include/linux/of_reserved_mem.h new file +8 -0

new file mode 100644
index 0000000..c841282
@@ -0,0 +1,14 @@
+#ifndef __OF_RESERVED_MEM_H
+#define __OF_RESERVED_MEM_H
+
+#ifdef CONFIG_OF_RESERVED_MEM
+void of_reserved_mem_device_init(struct device *dev);
+void of_reserved_mem_device_release(struct device *dev);
+void early_init_dt_scan_reserved_mem(void);
+#else

Quoted 8 lines

Quoted 8 lines

include/linux/of_reserved_mem.h new file +6 -1

+static inline void of_reserved_mem_device_init(struct device *dev) { }
+static inline void of_reserved_mem_device_release(struct device *dev) { }
+static inline void early_init_dt_scan_reserved_mem(void) { }
+#endif
+
+#endif /* __OF_RESERVED_MEM_H */
--

1.7.9.5

Best regards

Signature · 8 lines

Marek Szyprowski
Samsung R&D Institute Poland


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Quoted 13 lines · Marek Szyprowski

Quoted 11 lines · Grant Likely

Documentation/devicetree/bindings/memory.txt line 59

Quoted 3 lines · Marek Szyprowski

Documentation/devicetree/bindings/memory.txt new file +3 -0

+	- "reserved-memory-region" - compatibility is defined, given
+	  region is assigned for exclusive usage for by the respective
+	  devices.

BTW, just so you're aware there is already a binding for marking regions as reserved. It was recently added to arch/powerpc/kernel/prom.c. Unfortunately it doesn't look like it got documented. Search for "reserved-ranges". However, I don't think it blocks your work here. That binding doesn't provide any way for matching devices to reserved ranges. It is only for telling the kernel "hands of that memory".

Quoted 1 line

ok, good to know.

So I think the most generic compatible should effectively be the same as 'reserved-ranges', ie this region shouldn't be touched by the kernel.

Than we can build on top of that with more specific compatibles.

I have examples from FSL networking SoCs where we would carve out memory for backing storage managed completely by the HW and Linux wouldn't need to touch it, however we might have a "fsl,qman-backing-store" compat encase we might want some debug code in linux to look at the region of memory.

I've got examples at qualcomm where we have shared data structures in specific memory regions between different processors that aren't cache coherent, so want the memory not to be marked as cacheable by Linux when it accesses it. Again we'd have a "qcom,smem" prop on top of the "reserved-memory-region".

Quoted 28 lines · Kumar Gala

Quoted 13 lines · Marek Szyprowski

Quoted 11 lines · Grant Likely

Documentation/devicetree/bindings/memory.txt line 59

Quoted 3 lines · Marek Szyprowski

Documentation/devicetree/bindings/memory.txt new file +3 -0

+	- "reserved-memory-region" - compatibility is defined, given
+	  region is assigned for exclusive usage for by the respective
+	  devices.

BTW, just so you're aware there is already a binding for marking regions as reserved. It was recently added to arch/powerpc/kernel/prom.c. Unfortunately it doesn't look like it got documented. Search for "reserved-ranges". However, I don't think it blocks your work here. That binding doesn't provide any way for matching devices to reserved ranges. It is only for telling the kernel "hands of that memory".

Quoted 1 line

ok, good to know.

So I think the most generic compatible should effectively be the same as 'reserved-ranges', ie this region shouldn't be touched by the kernel.

Than we can build on top of that with more specific compatibles.

I have examples from FSL networking SoCs where we would carve out memory for backing storage managed completely by the HW and Linux wouldn't need to touch it, however we might have a "fsl,qman-backing-store" compat encase we might want some debug code in linux to look at the region of memory.

Quoted 5 lines

I've got examples at qualcomm where we have shared data structures in specific memory regions between different processors that aren't cache coherent, so want the memory not to be marked as cacheable by Linux when it accesses it. Again we'd have a "qcom,smem" prop on top of the "reserved-memory-region".

I think that is a reasonable approach, and works really well for regions associated with specific hardware because the hardware driver can be responsible for wiring it up to CMA or manage the region directly. Whatever the driver desires to do.

It still remains what to do for generic regions that any device can use. As I've previously said, I don't like calling out "CMA" specifically in the compatible property because that happens to be a Linux implementation specific details. Two years from now someone may propose a new allocator that should take over what used to be handled by CMA (kind of like how CMA may end up taking over from ION)....

Alright, I've thought about it some more and it probably does make sense to use an additional compatible string. Marek originally suggested "linux,contiguous-memory-region". I later suggested "shareable-memory-region", but that's actually a worse name because it doesn't have any reference to what the region is for (I was fixating on the kernel being able to use unallocated pages; but that is also an implementation detail). I exercise my right to change my mind and agree that contiguous is appropriate here. But instead of calling out the contiguous allocator, the binding should specifically lay out the usage model for these regions. I would change the contiguous-memory binding to state the following:
Contiguous-memory is a region of general purpose memory from which large buffers of contiguous memory can be allocated. Contiguous buffers are often used for DMA buffers. The operating system may use the memory for any purpose, but must immediately release the pages if a contiguous buffer is required.

So the way I read things, the current proposal would be:

The generic form for do-not-touch memory:

	compatible = "reserved-memory";

- I've dropped '-region' because I think it is redundant
- The kernel will not make use of this memory except for when a driver picks it up

For contiguous memory:
compatible = "contiguous-memory", "reserved-memory"

For contiguous memory that Linux will use by default if a specific region isn't specified.

	compatible = "contiguous-memory", "reserved-memory"
	linux,default-contiguous-region;

- I stuck with a linux, prefix here because I haven't come up with a non-linux way to describe this.

Memory that specific hardware can pick up:
compatible = "qcom,smem", "reserved-memory"

Nodes with a 'size' property and without a 'reg' property need to have a region allocated and reserved. The allocated region needs to be cached somewhere. We could create a data structure for tracking the reserved regions, or could write it in directly. While I shudder at the thought of modifying the device tree at runtime by the kernel, it might just be the sanest implementation at this time. I'd like to see what the implementation looks like. (Since this is potentially controversial, I would recommend implementing the exact regions in on patch, and add dynamically allocated regions as a follow-up patch)

As far as proper implementation is concerned, I think it should be explicit in the binding that the kernel should automatically exclude anything under the reserved-memory node, regardless of the compatible value. Merely being a child of the reserved-memory node immediately means that it is a reserved memory region.

g.

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Quoted 71 lines · Grant Likely

Quoted 28 lines · Kumar Gala

Quoted 13 lines · Marek Szyprowski

Quoted 11 lines · Grant Likely

Documentation/devicetree/bindings/memory.txt line 59

Quoted 3 lines · Marek Szyprowski

Documentation/devicetree/bindings/memory.txt new file +3 -0

+	- "reserved-memory-region" - compatibility is defined, given
+	  region is assigned for exclusive usage for by the respective
+	  devices.

BTW, just so you're aware there is already a binding for marking regions as reserved. It was recently added to arch/powerpc/kernel/prom.c. Unfortunately it doesn't look like it got documented. Search for "reserved-ranges". However, I don't think it blocks your work here. That binding doesn't provide any way for matching devices to reserved ranges. It is only for telling the kernel "hands of that memory".

Quoted 1 line

ok, good to know.

So I think the most generic compatible should effectively be the same as 'reserved-ranges', ie this region shouldn't be touched by the kernel.

Than we can build on top of that with more specific compatibles.

I have examples from FSL networking SoCs where we would carve out memory for backing storage managed completely by the HW and Linux wouldn't need to touch it, however we might have a "fsl,qman-backing-store" compat encase we might want some debug code in linux to look at the region of memory.

Quoted 5 lines

I've got examples at qualcomm where we have shared data structures in specific memory regions between different processors that aren't cache coherent, so want the memory not to be marked as cacheable by Linux when it accesses it. Again we'd have a "qcom,smem" prop on top of the "reserved-memory-region".

I think that is a reasonable approach, and works really well for regions associated with specific hardware because the hardware driver can be responsible for wiring it up to CMA or manage the region directly. Whatever the driver desires to do.

It still remains what to do for generic regions that any device can use. As I've previously said, I don't like calling out "CMA" specifically in the compatible property because that happens to be a Linux implementation specific details. Two years from now someone may propose a new allocator that should take over what used to be handled by CMA (kind of like how CMA may end up taking over from ION)....

Alright, I've thought about it some more and it probably does make sense to use an additional compatible string. Marek originally suggested "linux,contiguous-memory-region". I later suggested "shareable-memory-region", but that's actually a worse name because it doesn't have any reference to what the region is for (I was fixating on the kernel being able to use unallocated pages; but that is also an implementation detail). I exercise my right to change my mind and agree that contiguous is appropriate here. But instead of calling out the contiguous allocator, the binding should specifically lay out the usage model for these regions. I would change the contiguous-memory binding to state the following:
Contiguous-memory is a region of general purpose memory from which large buffers of contiguous memory can be allocated. Contiguous buffers are often used for DMA buffers. The operating system may use the memory for any purpose, but must immediately release the pages if a contiguous buffer is required.

So the way I read things, the current proposal would be:

The generic form for do-not-touch memory:

	compatible = "reserved-memory";

- I've dropped '-region' because I think it is redundant
- The kernel will not make use of this memory except for when a driver picks it up

Quoted 2 lines

For contiguous memory:
compatible = "contiguous-memory", "reserved-memory"

Hmm.., what's an example of a generic use of this compatible set that isn't linux/CMA specific?

Quoted 11 lines

For contiguous memory that Linux will use by default if a specific region isn't specified.

	compatible = "contiguous-memory", "reserved-memory"
	linux,default-contiguous-region;

- I stuck with a linux, prefix here because I haven't come up with a non-linux way to describe this.

Memory that specific hardware can pick up:
compatible = "qcom,smem", "reserved-memory"

Quoted 9 lines

Nodes with a 'size' property and without a 'reg' property need to have a region allocated and reserved. The allocated region needs to be cached somewhere. We could create a data structure for tracking the reserved regions, or could write it in directly. While I shudder at the thought of modifying the device tree at runtime by the kernel, it might just be the sanest implementation at this time. I'd like to see what the implementation looks like. (Since this is potentially controversial, I would recommend implementing the exact regions in on patch, and add dynamically allocated regions as a follow-up patch)

curious, what's the example for this situation of not having a 'reg' but having a size?

The generic form for do-not-touch memory:

	compatible = "reserved-memory";

- I've dropped '-region' because I think it is redundant
- The kernel will not make use of this memory except for when a driver picks it up

For contiguous memory:
compatible = "contiguous-memory", "reserved-memory"

Quoted 6 lines · Grant Likely

The generic form for do-not-touch memory:

	compatible = "reserved-memory";

- I've dropped '-region' because I think it is redundant
- The kernel will not make use of this memory except for when a driver picks it up

Quoted 2 lines

For contiguous memory:
compatible = "contiguous-memory", "reserved-memory"

Should the phandle references still be 'memory-region' ?

Quoted 28 lines · Kumar Gala

Quoted 13 lines · Marek Szyprowski

Quoted 11 lines · Grant Likely

Documentation/devicetree/bindings/memory.txt line 59

Quoted 3 lines · Marek Szyprowski

Documentation/devicetree/bindings/memory.txt new file +3 -0

+	- "reserved-memory-region" - compatibility is defined, given
+	  region is assigned for exclusive usage for by the respective
+	  devices.

BTW, just so you're aware there is already a binding for marking regions as reserved. It was recently added to arch/powerpc/kernel/prom.c. Unfortunately it doesn't look like it got documented. Search for "reserved-ranges". However, I don't think it blocks your work here. That binding doesn't provide any way for matching devices to reserved ranges. It is only for telling the kernel "hands of that memory".

Quoted 1 line

ok, good to know.

So I think the most generic compatible should effectively be the same as 'reserved-ranges', ie this region shouldn't be touched by the kernel.

Than we can build on top of that with more specific compatibles.

I have examples from FSL networking SoCs where we would carve out memory for backing storage managed completely by the HW and Linux wouldn't need to touch it, however we might have a "fsl,qman-backing-store" compat encase we might want some debug code in linux to look at the region of memory.

Quoted 5 lines

I've got examples at qualcomm where we have shared data structures in specific memory regions between different processors that aren't cache coherent, so want the memory not to be marked as cacheable by Linux when it accesses it. Again we'd have a "qcom,smem" prop on top of the "reserved-memory-region".

I think that is a reasonable approach, and works really well for regions associated with specific hardware because the hardware driver can be responsible for wiring it up to CMA or manage the region directly. Whatever the driver desires to do.

It still remains what to do for generic regions that any device can use. As I've previously said, I don't like calling out "CMA" specifically in the compatible property because that happens to be a Linux implementation specific details. Two years from now someone may propose a new allocator that should take over what used to be handled by CMA (kind of like how CMA may end up taking over from ION)....

Alright, I've thought about it some more and it probably does make sense to use an additional compatible string. Marek originally suggested "linux,contiguous-memory-region". I later suggested "shareable-memory-region", but that's actually a worse name because it doesn't have any reference to what the region is for (I was fixating on the kernel being able to use unallocated pages; but that is also an implementation detail). I exercise my right to change my mind and agree that contiguous is appropriate here. But instead of calling out the contiguous allocator, the binding should specifically lay out the usage model for these regions. I would change the contiguous-memory binding to state the following:
Contiguous-memory is a region of general purpose memory from which large buffers of contiguous memory can be allocated. Contiguous buffers are often used for DMA buffers. The operating system may use the memory for any purpose, but must immediately release the pages if a contiguous buffer is required.

So the way I read things, the current proposal would be:

The generic form for do-not-touch memory:

	compatible = "reserved-memory";

- I've dropped '-region' because I think it is redundant
- The kernel will not make use of this memory except for when a driver picks it up

For contiguous memory:
compatible = "contiguous-memory", "reserved-memory"

For contiguous memory that Linux will use by default if a specific region isn't specified.

	compatible = "contiguous-memory", "reserved-memory"
	linux,default-contiguous-region;

- I stuck with a linux, prefix here because I haven't come up with a non-linux way to describe this.

Memory that specific hardware can pick up:
compatible = "qcom,smem", "reserved-memory"

Nodes with a 'size' property and without a 'reg' property need to have a region allocated and reserved. The allocated region needs to be cached somewhere. We could create a data structure for tracking the reserved regions, or could write it in directly. While I shudder at the thought of modifying the device tree at runtime by the kernel, it might just be the sanest implementation at this time. I'd like to see what the implementation looks like. (Since this is potentially controversial, I would recommend implementing the exact regions in on patch, and add dynamically allocated regions as a follow-up patch)

As far as proper implementation is concerned, I think it should be explicit in the binding that the kernel should automatically exclude anything under the reserved-memory node, regardless of the compatible value. Merely being a child of the reserved-memory node immediately means that it is a reserved memory region.

Fixing those issues requires further discussion. Frankly, right now I really have no idea which way should I go. The /reserved-ranges node seems to be easy to match particular reserved memory region with a given device. I'm also not really convinced if it makes sense to add a code for finding and matching a reserved memory region to every device driver, which might need it. I would really like to get some more feedback on the Ben's comment.

In any case, the code will also change significantly, so I assume that the best, what can be done now is to revert the current version and start from the scratch with a new, complete proposal.

Quoted 9 lines · Marek Szyprowski

Fixing those issues requires further discussion. Frankly, right now I really have no idea which way should I go. The /reserved-ranges node seems to be easy to match particular reserved memory region with a given device. I'm also not really convinced if it makes sense to add a code for finding and matching a reserved memory region to every device driver, which might need it. I would really like to get some more feedback on the Ben's comment.

Quoted 3 lines

In any case, the code will also change significantly, so I assume that the best, what can be done now is to revert the current version and start from the scratch with a new, complete proposal.

Yes, let's do that. I will try to help. It shouldn't be that a big deal.

Quoted 14 lines · Benjamin Herrenschmidt

Quoted 12 lines · Marek Szyprowski

Fixing those issues requires further discussion. Frankly, right now I really have no idea which way should I go. The /reserved-ranges node seems to be easy to match particular reserved memory region with a given device. I'm also not really convinced if it makes sense to add a code for finding and matching a reserved memory region to every device driver, which might need it. I would really like to get some more feedback on the Ben's comment.

In any case, the code will also change significantly, so I assume that the best, what can be done now is to revert the current version and start from the scratch with a new, complete proposal.

Quoted 1 line

Yes, let's do that. I will try to help. It shouldn't be that a big deal.

I think we can get the concerns sorted quickly. I'm at meetings all day today in SJC, but I'll take a look at it this evening. I'll be in Edinburgh. We're holding an ARM summit at the same time so a bunch of affected ARM folks will be there.

Quoted 16 lines · Grant Likely

Quoted 14 lines · Benjamin Herrenschmidt

Quoted 12 lines · Marek Szyprowski

Fixing those issues requires further discussion. Frankly, right now I really have no idea which way should I go. The /reserved-ranges node seems to be easy to match particular reserved memory region with a given device. I'm also not really convinced if it makes sense to add a code for finding and matching a reserved memory region to every device driver, which might need it. I would really like to get some more feedback on the Ben's comment.

In any case, the code will also change significantly, so I assume that the best, what can be done now is to revert the current version and start from the scratch with a new, complete proposal.

Quoted 6 lines

Quoted 1 line

Yes, let's do that. I will try to help. It shouldn't be that a big deal.

I think we can get the concerns sorted quickly. I'm at meetings all day today in SJC, but I'll take a look at it this evening. I'll be in Edinburgh. We're holding an ARM summit at the same time so a bunch of affected ARM folks will be there.

After reading through the entirety of the other thread, I think this can be fixed. My preference would be to fix in now rather than waiting another cycle. If you haven't sent the revert yet then please hold off for a bit (I can't tell at the moment since I'm currently on an airplane and I didn't update my tree before leaving the ground).

Hello,

Quoted 103 lines · Grant Likely

Quoted 3 lines · Kumar Gala

Quoted 2 lines · Marek Szyprowski

Quoted 1 line · Grant Likely

On Mon, 26 Aug 2013 16:39:18 +0200, Marek Szyprowski

Quoted 2 lines · <[email protected]> wrote:

Quoted 2 lines

Quoted 2 lines

Review

Quoted 2 lines

(quoted diff) +2 -0

+    - "reserved-memory-region" - compatibility is defined, given
+      region is assigned for exclusive usage for by the 

respective

Quoted 3 lines

Quoted 3 lines

Quoted 3 lines

Quoted 1 line

+ devices.

BTW, just so you're aware there is already a binding for marking

regions

Quoted 3 lines

Quoted 3 lines

Quoted 3 lines

as reserved. It was recently added to arch/powerpc/kernel/prom.c. Unfortunately it doesn't look like it got documented. Search for "reserved-ranges". However, I don't think it blocks your work

here. That

Quoted 1 line

Quoted 1 line

Quoted 1 line

binding doesn't provide any way for matching devices to reserved

ranges.

Quoted 16 lines

Quoted 3 lines

Quoted 1 line

It is only for telling the kernel "hands of that memory".

ok, good to know.

So I think the most generic compatible should effectively be the same as 'reserved-ranges', ie this region shouldn't be touched by the kernel.

Than we can build on top of that with more specific compatibles.

I have examples from FSL networking SoCs where we would carve out memory for backing storage managed completely by the HW and Linux wouldn't need to touch it, however we might have a "fsl,qman-backing-store" compat encase we might want some debug code in linux to look at the region of memory.

Quoted 5 lines

I've got examples at qualcomm where we have shared data structures in specific memory regions between different processors that aren't cache coherent, so want the memory not to be marked as cacheable by Linux when it accesses it. Again we'd have a "qcom,smem" prop on top of the "reserved-memory-region".

I think that is a reasonable approach, and works really well for regions associated with specific hardware because the hardware driver can be responsible for wiring it up to CMA or manage the region directly. Whatever the driver desires to do.

It still remains what to do for generic regions that any device can use. As I've previously said, I don't like calling out "CMA" specifically in the compatible property because that happens to be a Linux implementation specific details. Two years from now someone may propose a new allocator that should take over what used to be handled by CMA (kind of like how CMA may end up taking over from ION)....

Alright, I've thought about it some more and it probably does make sense to use an additional compatible string. Marek originally suggested "linux,contiguous-memory-region". I later suggested "shareable-memory-region",
but that's actually a worse name because it doesn't have any reference to what the region is for (I was fixating on the kernel being able to use unallocated pages; but that is also an implementation detail). I exercise my right to change my mind and agree that contiguous is appropriate here. But instead of calling out the contiguous allocator, the binding should specifically lay out the usage model for these regions. I would change the contiguous-memory binding to state the following:
Contiguous-memory is a region of general purpose memory from which large buffers of contiguous memory can be allocated. Contiguous buffers are often used for DMA buffers. The operating system may use the memory for any purpose, but must immediately release the pages if a contiguous buffer is required.

So the way I read things, the current proposal would be:

The generic form for do-not-touch memory:

    compatible = "reserved-memory";

- I've dropped '-region' because I think it is redundant
- The kernel will not make use of this memory except for when a
driver picks it up

For contiguous memory:
compatible = "contiguous-memory", "reserved-memory"

For contiguous memory that Linux will use by default if a specific region isn't specified.
compatible = "contiguous-memory", "reserved-memory" linux,default-contiguous-region;
- I stuck with a linux, prefix here because I haven't come up with a non-linux way to describe this.

Memory that specific hardware can pick up:
compatible = "qcom,smem", "reserved-memory"

Nodes with a 'size' property and without a 'reg' property need to have a region allocated and reserved. The allocated region needs to be cached somewhere. We could create a data structure for tracking the reserved regions, or could write it in directly. While I shudder at the thought of
modifying the device tree at runtime by the kernel, it might just be the sanest implementation at this time. I'd like to see what the implementation looks like. (Since this is potentially controversial, I would recommend implementing the exact regions in on patch, and add dynamically allocated regions as a follow-up patch)

Quoted 5 lines

As far as proper implementation is concerned, I think it should be explicit in the binding that the kernel should automatically exclude anything under the reserved-memory node, regardless of the compatible value. Merely being a child of the reserved-memory node immediately means that it is a reserved memory region.

It looks that my proposal for the reserved memory nodes causes much more controversy than I expected when I've sent a pull request to Linus:
https://lkml.org/lkml/2013/9/15/151
http://www.spinics.net/lists/arm-kernel/msg273548.html

Fixing those issues requires further discussion. Frankly, right now I really have no idea which way should I go. The /reserved-ranges node seems
to be easy to match particular reserved memory region with a given device.

I'm also not really convinced if it makes sense to add a code for finding and matching a reserved memory region to every device driver, which might need it. I would really like to get some more feedback on the Ben's comment.

In any case, the code will also change significantly, so I assume that the
best, what can be done now is to revert the current version and start from
the scratch with a new, complete proposal.

Hello,

Quoted 97 lines · Grant Likely

Quoted 16 lines · Marek Szyprowski

This patch adds device tree support for contiguous and reserved memory regions defined in device tree.

Large memory blocks can be reliably reserved only during early boot. This must happen before the whole memory management subsystem is initialized, because we need to ensure that the given contiguous blocks are not yet allocated by kernel. Also it must happen before kernel mappings for the whole low memory are created, to ensure that there will be no mappings (for reserved blocks) or mapping with special properties can be created (for CMA blocks). This all happens before device tree structures are unflattened, so we need to get reserved memory layout directly from fdt.

Later, those reserved memory regions are assigned to devices on each device structure initialization.

Quoted 6 lines

Signed-off-by Marek Szyprowski <[email protected]>

Acked-by Kyungmin Park <[email protected]>

Acked-by Michal Nazarewicz <[email protected]>

Acked-by Tomasz Figa <[email protected]>

Acked-by Stephen Warren <[email protected]>

Reviewed-by Rob Herring <[email protected]>

Hi Marek,

This patch is in good shape, but I have some comments below and a few concerns about the binding....

g.

Quoted 66 lines

---
 Documentation/devicetree/bindings/memory.txt |  168 +++++++++++++++++++++++++
 drivers/of/Kconfig                           |    6 +
 drivers/of/Makefile                          |    1 +
 drivers/of/of_reserved_mem.c                 |  175 ++++++++++++++++++++++++++
 drivers/of/platform.c                        |    4 +
 include/linux/of_reserved_mem.h              |   14 +++
 6 files changed, 368 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/memory.txt
 create mode 100644 drivers/of/of_reserved_mem.c
 create mode 100644 include/linux/of_reserved_mem.h

Documentation/devicetree/bindings/memory.txt new file +48 -0

new file mode 100644
index 0000000..eb24693
@@ -0,0 +1,168 @@
+*** Memory binding ***
+
+The /memory node provides basic information about the address and size
+of the physical memory. This node is usually filled or updated by the
+bootloader, depending on the actual memory configuration of the given
+hardware.
+
+The memory layout is described by the following node:
+
+/ {
+	#address-cells = <(n)>;
+	#size-cells = <(m)>;
+	memory {
+		device_type = "memory";
+		reg =  <(baseaddr1) (size1)
+			(baseaddr2) (size2)
+			...
+			(baseaddrN) (sizeN)>;
+	};
+	...
+};
+
+A memory node follows the typical device tree rules for "reg" property:
+n:		number of cells used to store base address value
+m:		number of cells used to store size value
+baseaddrX:	defines a base address of the defined memory bank
+sizeX:		the size of the defined memory bank
+
+
+More than one memory bank can be defined.
+
+
+*** Reserved memory regions ***
+
+In /memory/reserved-memory node one can create child nodes describing
+particular reserved (excluded from normal use) memory regions. Such
+memory regions are usually designed for the special usage by various
+device drivers. A good example are contiguous memory allocations or
+memory sharing with other operating system on the same hardware board.
+Those special memory regions might depend on the board configuration and
+devices used on the target system.
+
+Parameters for each memory region can be encoded into the device tree
+with the following convention:
+
+[(label):] (name) {
+	compatible = "linux,contiguous-memory-region", "reserved-memory-region";
+	reg = <(address) (size)>;

Quoted 8 lines

Documentation/devicetree/bindings/memory.txt line 52

Quoted 4 lines

Documentation/devicetree/bindings/memory.txt new file +4 -0

+	(linux,default-contiguous-region);
+};
+
+compatible:	one or more of:

It's unclear what the meaning of having both values means for the kernel. Does it mean the regions is sharable with the kernel or not? I would think they are mutually exclusive.

I consider CMA ("linux,contiguous-memory-region") as a special case of the reserved memory driver. The main advantage is the ability of sharing the memory
with the system instead of just allocating it from the carved out memory region. From the device and hardware perspective there is no difference if the buffer comes from CMA or reserved memory. However if you insist, I can change it to something different, like "shareable-memory-region".

Specifying both compatible values would let kernel to bind the more specific driver (cma, if available) over the generic one (simple reserved memory carve-out allocator based on dma_coherent).

Quoted 12 lines

Documentation/devicetree/bindings/memory.txt line 56

Quoted 5 lines

Documentation/devicetree/bindings/memory.txt new file +4 -0

+	- "linux,contiguous-memory-region" - enables binding of this
+	  region to Contiguous Memory Allocator (special region for
+	  contiguous memory allocations, shared with movable system
+	  memory, Linux kernel-specific).

As mentioned in the older thread, you can drop the 'linux,' prefix here. Perhaps something like "shareable-memory-region" or merely "memory-region". It is reasonable for any kernel (not just Linux) to use marked regions for movable pages until it gets requested by a driver, in which case a rather generic "memory-region" makes a lot of sense as a name.

Quoted 11 lines

Documentation/devicetree/bindings/memory.txt line 59

Quoted 4 lines

Documentation/devicetree/bindings/memory.txt new file +3 -0

+	- "reserved-memory-region" - compatibility is defined, given
+	  region is assigned for exclusive usage for by the respective
+	  devices.

BTW, just so you're aware there is already a binding for marking regions as reserved. It was recently added to arch/powerpc/kernel/prom.c. Unfortunately it doesn't look like it got documented. Search for "reserved-ranges". However, I don't think it blocks your work here. That binding doesn't provide any way for matching devices to reserved ranges. It is only for telling the kernel "hands of that memory".

ok, good to know.

Quoted 8 lines

Quoted 8 lines

Documentation/devicetree/bindings/memory.txt new file +8 -0

+
+reg:	standard property defining the base address and size of
+	the memory region
+
+linux,default-contiguous-region: property indicating that the region
+	is the default region for all contiguous memory
+	allocations, Linux specific (optional)
+

Quoted 8 lines

Documentation/devicetree/bindings/memory.txt line 70

Quoted 3 lines

Documentation/devicetree/bindings/memory.txt new file +3 -0

+It is optional to specify the base address, so if one wants to use
+autoconfiguration of the base address, '0' can be specified as a base
+address in the 'reg' property.

I don't understand this. What does autoconfiguration of the base address actually do? If this is intended to dynamically allocate a region of RAM for contiguous allocations, then don't use 'reg'. Use a different property that only specifies the size.

Ok, I will try to make a patch which removes special 'zero' base address handling and adds separate 'size' property for automatically configured regions.

Quoted 7 lines

Documentation/devicetree/bindings/memory.txt line 73

Quoted 2 lines

Documentation/devicetree/bindings/memory.txt new file +2 -0

+The /memory/reserved-memory node must contain the same #address-cells
+and #size-cells value as the root node.

That seems to be an arbitrary restriction. Why does the reserved-memory node need to have exactly the same #address/size values? The 'reg' property binding quite easily handles different values at different levels of the tree. More below....

Does it really makes sense to have such configuration with different #address-cells/#size-cells than the root memory node?

drivers/of/platform.c +1 -0

index e0a6514..eeca8a5 100644
@@ -21,6 +21,7 @@
 #include <linux/of_device.h>
 #include <linux/of_irq.h>
 #include <linux/of_platform.h>
+#include <linux/of_reserved_mem.h>
 #include <linux/platform_device.h>
 
 const struct of_device_id of_default_bus_match_table[] = {

drivers/of/platform.c +1 -0

 	/* We do not fill the DMA ops for platform devices by default.
 	 * This is currently the responsibility of the platform code
 	 * to do such, possibly using a device notifier

@@ -225,6 +228,7 @@ struct platform_device *of_platform_device_create_pdata(
 
 	if (of_device_add(dev) != 0) {
 		platform_device_put(dev);
+		of_reserved_mem_device_release(&dev->dev);
 		return NULL;
 	}
 

include/linux/of_reserved_mem.h new file +14 -0

new file mode 100644
index 0000000..c841282
@@ -0,0 +1,14 @@
+#ifndef __OF_RESERVED_MEM_H
+#define __OF_RESERVED_MEM_H
+
+#ifdef CONFIG_OF_RESERVED_MEM
+void of_reserved_mem_device_init(struct device *dev);
+void of_reserved_mem_device_release(struct device *dev);
+void early_init_dt_scan_reserved_mem(void);
+#else
+static inline void of_reserved_mem_device_init(struct device *dev) { }
+static inline void of_reserved_mem_device_release(struct device *dev) { }
+static inline void early_init_dt_scan_reserved_mem(void) { }
+#endif
+
+#endif /* __OF_RESERVED_MEM_H */

Signature · 1 line

1.7.9.5

drivers/of/of_reserved_mem.c new file +7 -0

+/**
+ * of_reserved_mem_device_init() - assign reserved memory region to given device
+ *
+ * This function assign memory region pointed by "memory-region" device tree
+ * property to the given device.
+ */
+void of_reserved_mem_device_init(struct device *dev)

This patch adds device tree support for contiguous and reserved memory regions defined in device tree.

Large memory blocks can be reliably reserved only during early boot. This must happen before the whole memory management subsystem is initialized, because we need to ensure that the given contiguous blocks are not yet allocated by kernel. Also it must happen before kernel mappings for the whole low memory are created, to ensure that there will be no mappings (for reserved blocks) or mapping with special properties can be created (for CMA blocks). This all happens before device tree structures are unflattened, so we need to get reserved memory layout directly from fdt.

Later, those reserved memory regions are assigned to devices on each device structure initialization.

Signed-off-by Marek Szyprowski <[email protected]>

Acked-by Kyungmin Park <[email protected]>

Acked-by Michal Nazarewicz <[email protected]>

Acked-by Tomasz Figa <[email protected]>

Acked-by Stephen Warren <[email protected]>

Reviewed-by Rob Herring <[email protected]>

---
 Documentation/devicetree/bindings/memory.txt |  168 +++++++++++++++++++++++++
 drivers/of/Kconfig                           |    6 +
 drivers/of/Makefile                          |    1 +
 drivers/of/of_reserved_mem.c                 |  175 ++++++++++++++++++++++++++
 drivers/of/platform.c                        |    4 +
 include/linux/of_reserved_mem.h              |   14 +++
 6 files changed, 368 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/memory.txt
 create mode 100644 drivers/of/of_reserved_mem.c
 create mode 100644 include/linux/of_reserved_mem.h

Documentation/devicetree/bindings/memory.txt new file +168 -0

new file mode 100644
index 0000000..eb24693
@@ -0,0 +1,168 @@
+*** Memory binding ***
+
+The /memory node provides basic information about the address and size
+of the physical memory. This node is usually filled or updated by the
+bootloader, depending on the actual memory configuration of the given
+hardware.
+
+The memory layout is described by the following node:
+
+/ {
+       #address-cells = <(n)>;
+       #size-cells = <(m)>;
+       memory {
+               device_type = "memory";
+               reg =  <(baseaddr1) (size1)
+                       (baseaddr2) (size2)
+                       ...
+                       (baseaddrN) (sizeN)>;
+       };
+       ...
+};
+
+A memory node follows the typical device tree rules for "reg" property:
+n:             number of cells used to store base address value
+m:             number of cells used to store size value
+baseaddrX:     defines a base address of the defined memory bank
+sizeX:         the size of the defined memory bank
+
+
+More than one memory bank can be defined.
+
+
+*** Reserved memory regions ***
+
+In /memory/reserved-memory node one can create child nodes describing
+particular reserved (excluded from normal use) memory regions. Such
+memory regions are usually designed for the special usage by various
+device drivers. A good example are contiguous memory allocations or
+memory sharing with other operating system on the same hardware board.
+Those special memory regions might depend on the board configuration and
+devices used on the target system.
+
+Parameters for each memory region can be encoded into the device tree
+with the following convention:
+
+[(label):] (name) {
+       compatible = "linux,contiguous-memory-region", "reserved-memory-region";
+       reg = <(address) (size)>;
+       (linux,default-contiguous-region);
+};
+
+compatible:    one or more of:
+       - "linux,contiguous-memory-region" - enables binding of this
+         region to Contiguous Memory Allocator (special region for
+         contiguous memory allocations, shared with movable system
+         memory, Linux kernel-specific).
+       - "reserved-memory-region" - compatibility is defined, given
+         region is assigned for exclusive usage for by the respective
+         devices.
+
+reg:   standard property defining the base address and size of
+       the memory region
+
+linux,default-contiguous-region: property indicating that the region
+       is the default region for all contiguous memory
+       allocations, Linux specific (optional)
+
+It is optional to specify the base address, so if one wants to use
+autoconfiguration of the base address, '0' can be specified as a base
+address in the 'reg' property.
+
+The /memory/reserved-memory node must contain the same #address-cells
+and #size-cells value as the root node.
+
+
+*** Device node's properties ***
+
+Once regions in the /memory/reserved-memory node have been defined, they
+may be referenced by other device nodes. Bindings that wish to reference
+memory regions should explicitly document their use of the following
+property:
+
+memory-region = <&phandle_to_defined_region>;
+
+This property indicates that the device driver should use the memory
+region pointed by the given phandle.
+
+
+*** Example ***
+
+This example defines a memory consisting of 4 memory banks. 3 contiguous
+regions are defined for Linux kernel, one default of all device drivers
+(named contig_mem, placed at 0x72000000, 64MiB), one dedicated to the
+framebuffer device (labelled display_mem, placed at 0x78000000, 8MiB)
+and one for multimedia processing (labelled multimedia_mem, placed at
+0x77000000, 64MiB). 'display_mem' region is then assigned to fb at 12300000
+device for DMA memory allocations (Linux kernel drivers will use CMA is
+available or dma-exclusive usage otherwise). 'multimedia_mem' is
+assigned to scaler at 12500000 and codec at 12600000 devices for contiguous
+memory allocations when CMA driver is enabled.
+
+The reason for creating a separate region for framebuffer device is to
+match the framebuffer base address to the one configured by bootloader,
+so once Linux kernel drivers starts no glitches on the displayed boot
+logo appears. Scaller and codec drivers should share the memory
+allocations.
+
+/ {
+       #address-cells = <1>;
+       #size-cells = <1>;
+
+       /* ... */
+
+       memory {
+               reg =  <0x40000000 0x10000000
+                       0x50000000 0x10000000
+                       0x60000000 0x10000000
+                       0x70000000 0x10000000>;
+
+               reserved-memory {
+                       #address-cells = <1>;
+                       #size-cells = <1>;
+
+                       /*
+                        * global autoconfigured region for contiguous allocations
+                        * (used only with Contiguous Memory Allocator)
+                        */
+                       contig_region at 0 {
+                               compatible = "linux,contiguous-memory-region";
+                               reg = <0x0 0x4000000>;
+                               linux,default-contiguous-region;
+                       };
+
+                       /*
+                        * special region for framebuffer
+                        */
+                       display_region: region at 78000000 {
+                               compatible = "linux,contiguous-memory-region", "reserved-memory-region";
+                               reg = <0x78000000 0x800000>;
+                       };
+
+                       /*
+                        * special region for multimedia processing devices
+                        */
+                       multimedia_region: region at 77000000 {
+                               compatible = "linux,contiguous-memory-region";
+                               reg = <0x77000000 0x4000000>;
+                       };
+               };
+       };
+
+       /* ... */
+
+       fb0: fb at 12300000 {
+               status = "okay";
+               memory-region = <&display_region>;
+       };
+
+       scaler: scaler at 12500000 {
+               status = "okay";
+               memory-region = <&multimedia_region>;
+       };
+
+       codec: codec at 12600000 {
+               status = "okay";
+               memory-region = <&multimedia_region>;
+       };
+};

drivers/of/Kconfig +6 -0

index 80e5c13..f7107fa 100644
@@ -80,4 +80,10 @@ config OF_MTD
        depends on MTD
        def_bool y
 
+config OF_RESERVED_MEM
+       depends on DMA_CMA || (HAVE_GENERIC_DMA_COHERENT && HAVE_MEMBLOCK)
+       def_bool y
+       help
+         Initialization code for DMA reserved memory
+
 endmenu # OF

drivers/of/Makefile +1 -0

index 1f9c0c4..e7e3322 100644
@@ -10,3 +10,4 @@ obj-$(CONFIG_OF_MDIO) += of_mdio.o
 obj-$(CONFIG_OF_PCI)   += of_pci.o
 obj-$(CONFIG_OF_PCI_IRQ)  += of_pci_irq.o
 obj-$(CONFIG_OF_MTD)   += of_mtd.o
+obj-$(CONFIG_OF_RESERVED_MEM) += of_reserved_mem.o

drivers/of/of_reserved_mem.c new file +175 -0

new file mode 100644
index 0000000..a754b84
@@ -0,0 +1,175 @@
+/*
+ * Device tree based initialization code for reserved memory.
+ *
+ * Copyright (c) 2013 Samsung Electronics Co., Ltd.
+ *             http://www.samsung.com
+ * Author: Marek Szyprowski <[email protected]>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License or (at your optional) any later version of the license.
+ */
+
+#include <asm/dma-contiguous.h>
+
+#include <linux/memblock.h>
+#include <linux/err.h>
+#include <linux/of.h>
+#include <linux/of_fdt.h>
+#include <linux/of_platform.h>
+#include <linux/mm.h>
+#include <linux/sizes.h>
+#include <linux/mm_types.h>
+#include <linux/dma-contiguous.h>
+#include <linux/dma-mapping.h>
+#include <linux/of_reserved_mem.h>
+
+#define MAX_RESERVED_REGIONS   16
+struct reserved_mem {
+       phys_addr_t             base;
+       unsigned long           size;
+       struct cma              *cma;
+       char                    name[32];
+};
+static struct reserved_mem reserved_mem[MAX_RESERVED_REGIONS];
+static int reserved_mem_count;
+
+static int __init fdt_scan_reserved_mem(unsigned long node, const char *uname,
+                                       int depth, void *data)
+{
+       struct reserved_mem *rmem = &reserved_mem[reserved_mem_count];
+       phys_addr_t base, size;
+       int is_cma, is_reserved;
+       unsigned long len;
+       const char *status;
+       __be32 *prop;
+
+       is_cma = IS_ENABLED(CONFIG_DMA_CMA) &&
+              of_flat_dt_is_compatible(node, "linux,contiguous-memory-region");
+       is_reserved = of_flat_dt_is_compatible(node, "reserved-memory-region");
+
+       if (!is_reserved && !is_cma) {
+               /* ignore node and scan next one */
+               return 0;
+       }
+
+       status = of_get_flat_dt_prop(node, "status", &len);
+       if (status && strcmp(status, "okay") != 0) {
+               /* ignore disabled node nad scan next one */
+               return 0;
+       }
+
+       prop = of_get_flat_dt_prop(node, "reg", &len);
+       if (!prop || (len < (dt_root_size_cells + dt_root_addr_cells) *
+                            sizeof(__be32))) {
+               pr_err("Reserved mem: node %s, incorrect \"reg\" property\n",
+                      uname);
+               /* ignore node and scan next one */
+               return 0;
+       }
+       base = dt_mem_next_cell(dt_root_addr_cells, &prop);
+       size = dt_mem_next_cell(dt_root_size_cells, &prop);
+
+       if (!size) {
+               /* ignore node and scan next one */
+               return 0;
+       }
+
+       pr_info("Reserved mem: found %s, memory base %lx, size %ld MiB\n",
+               uname, (unsigned long)base, (unsigned long)size / SZ_1M);
+
+       if (reserved_mem_count == ARRAY_SIZE(reserved_mem))
+               return -ENOSPC;
+
+       rmem->base = base;
+       rmem->size = size;
+       strlcpy(rmem->name, uname, sizeof(rmem->name));
+
+       if (is_cma) {
+               struct cma *cma;
+               if (dma_contiguous_reserve_area(size, base, 0, &cma) == 0) {
+                       rmem->cma = cma;
+                       reserved_mem_count++;
+                       if (of_get_flat_dt_prop(node,
+                                               "linux,default-contiguous-region",
+                                               NULL))
+                               dma_contiguous_set_default(cma);
+               }
+       } else if (is_reserved) {
+               if (memblock_remove(base, size) == 0)
+                       reserved_mem_count++;
+               else
+                       pr_err("Failed to reserve memory for %s\n", uname);
+       }
+
+       return 0;
+}
+
+static struct reserved_mem *get_dma_memory_region(struct device *dev)
+{
+       struct device_node *node;
+       const char *name;
+       int i;
+
+       node = of_parse_phandle(dev->of_node, "memory-region", 0);
+       if (!node)
+               return NULL;
+
+       name = kbasename(node->full_name);
+       for (i = 0; i < reserved_mem_count; i++)
+               if (strcmp(name, reserved_mem[i].name) == 0)
+                       return &reserved_mem[i];
+       return NULL;
+}
+
+/**
+ * of_reserved_mem_device_init() - assign reserved memory region to given device
+ *
+ * This function assign memory region pointed by "memory-region" device tree
+ * property to the given device.
+ */
+void of_reserved_mem_device_init(struct device *dev)
+{
+       struct reserved_mem *region = get_dma_memory_region(dev);
+       if (!region)
+               return;
+
+       if (region->cma) {
+               dev_set_cma_area(dev, region->cma);
+               pr_info("Assigned CMA %s to %s device\n", region->name,
+                       dev_name(dev));
+       } else {
+               if (dma_declare_coherent_memory(dev, region->base, region->base,
+                   region->size, DMA_MEMORY_MAP | DMA_MEMORY_EXCLUSIVE) != 0)
+                       pr_info("Declared reserved memory %s to %s device\n",
+                               region->name, dev_name(dev));
+       }
+}
+
+/**
+ * of_reserved_mem_device_release() - release reserved memory device structures
+ *
+ * This function releases structures allocated for memory region handling for
+ * the given device.
+ */
+void of_reserved_mem_device_release(struct device *dev)
+{
+       struct reserved_mem *region = get_dma_memory_region(dev);
+       if (!region && !region->cma)
+               dma_release_declared_memory(dev);
+}
+
+/**
+ * early_init_dt_scan_reserved_mem() - create reserved memory regions
+ *
+ * This function grabs memory from early allocator for device exclusive use
+ * defined in device tree structures. It should be called by arch specific code
+ * once the early allocator (memblock) has been activated and all other
+ * subsystems have already allocated/reserved memory.
+ */
+void __init early_init_dt_scan_reserved_mem(void)
+{
+       of_scan_flat_dt_by_path("/memory/reserved-memory",
+                               fdt_scan_reserved_mem, NULL);
+}

drivers/of/platform.c +4 -0

index e0a6514..eeca8a5 100644
@@ -21,6 +21,7 @@
 #include <linux/of_device.h>
 #include <linux/of_irq.h>
 #include <linux/of_platform.h>
+#include <linux/of_reserved_mem.h>
 #include <linux/platform_device.h>
 
 const struct of_device_id of_default_bus_match_table[] = {

@@ -218,6 +219,8 @@ struct platform_device *of_platform_device_create_pdata(
        dev->dev.bus = &platform_bus_type;
        dev->dev.platform_data = platform_data;
 
+       of_reserved_mem_device_init(&dev->dev);
+
        /* We do not fill the DMA ops for platform devices by default.
         * This is currently the responsibility of the platform code
         * to do such, possibly using a device notifier

@@ -225,6 +228,7 @@ struct platform_device *of_platform_device_create_pdata(
 
        if (of_device_add(dev) != 0) {
                platform_device_put(dev);
+               of_reserved_mem_device_release(&dev->dev);
                return NULL;
        }
 

include/linux/of_reserved_mem.h new file +14 -1

new file mode 100644
index 0000000..c841282
@@ -0,0 +1,14 @@
+#ifndef __OF_RESERVED_MEM_H
+#define __OF_RESERVED_MEM_H
+
+#ifdef CONFIG_OF_RESERVED_MEM
+void of_reserved_mem_device_init(struct device *dev);
+void of_reserved_mem_device_release(struct device *dev);
+void early_init_dt_scan_reserved_mem(void);
+#else
+static inline void of_reserved_mem_device_init(struct device *dev) { }
+static inline void of_reserved_mem_device_release(struct device *dev) { }
+static inline void early_init_dt_scan_reserved_mem(void) { }
+#endif
+
+#endif /* __OF_RESERVED_MEM_H */
--

1.7.9.5

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linux-arm-kernel at lists.infradead.org
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Enable reserved memory initialization from device tree.

Signed-off-by Marek Szyprowski <[email protected]>

Acked-by Kyungmin Park <[email protected]>

Acked-by Michal Nazarewicz <[email protected]>

Acked-by Tomasz Figa <[email protected]>

---
 arch/arm/mm/init.c |    3 +++
 1 file changed, 3 insertions(+)

arch/arm/mm/init.c +1 -0

index 15225d8..6a2fe44 100644
@@ -17,6 +17,7 @@
 #include <linux/nodemask.h>
 #include <linux/initrd.h>
 #include <linux/of_fdt.h>
+#include <linux/of_reserved_mem.h>
 #include <linux/highmem.h>
 #include <linux/gfp.h>
 #include <linux/memblock.h>