nvmem: add fixed cells layout

From: Rafał Miłecki <[email protected]>

With the introduction of NVMEM layouts, new NVMEM content structures should be defined as such. We should also try to convert / migrate existing NVMEM content bindings to layouts.

This commit handles fixed NVMEM cells. So far they had to be defined directly - as device subnodes. With this change it's allowed to put them in the DT node named "nvmem-layout".

Having NVMEM cells in separated node is preferred as it draws a nice line between NVMEM device and its content. It results in cleaner bindings.

FWIW a very similar situation has happened to MTD devices and their
partitions: see commit 5d96ea42eb63 ("dt-bindings: mtd: Clarify all partition subnodes").

Signed-off-by Rafał Miłecki <[email protected]>

---
 .../bindings/nvmem/layouts/fixed-cell.yaml    | 31 ++++++++++++
 .../bindings/nvmem/layouts/fixed-layout.yaml  | 49 +++++++++++++++++++
 .../bindings/nvmem/layouts/nvmem-layout.yaml  |  5 +-
 .../devicetree/bindings/nvmem/nvmem.yaml      | 19 +------
 4 files changed, 83 insertions(+), 21 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/nvmem/layouts/fixed-cell.yaml
 create mode 100644 Documentation/devicetree/bindings/nvmem/layouts/fixed-layout.yaml

Documentation/devicetree/bindings/nvmem/layouts/fixed-cell.yaml new file +31 -0

new file mode 100644
index 000000000000..e698098450e1
@@ -0,0 +1,31 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/nvmem/layouts/fixed-cell.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Fixed offset & size NVMEM cell
+
+maintainers:
+  - Rafał Miłecki <[email protected]>
+  - Srinivas Kandagatla <[email protected]>
+
+properties:
+  reg:
+    maxItems: 1
+
+  bits:
+    $ref: /schemas/types.yaml#/definitions/uint32-array
+    items:
+      - minimum: 0
+        maximum: 7
+        description:
+          Offset in bit within the address range specified by reg.
+      - minimum: 1
+        description:
+          Size in bit within the address range specified by reg.
+
+required:
+  - reg
+
+additionalProperties: true

Documentation/devicetree/bindings/nvmem/layouts/fixed-layout.yaml new file +22 -0

new file mode 100644
index 000000000000..f7496ba28f33
@@ -0,0 +1,49 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/nvmem/layouts/fixed-layout.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: NVMEM layout for fixed NVMEM cells
+
+description:
+  Many NVMEM devices have hardcoded cells layout (offset and size of defined
+  NVMEM content doesn't change).
+
+  This binding allows defining such NVMEM layout with its cells. It can be used
+  on top of any NVMEM device.
+
+maintainers:
+  - Rafał Miłecki <[email protected]>
+
+properties:
+  compatible:
+    const: fixed-layout
+

Documentation/devicetree/bindings/nvmem/layouts/fixed-layout.yaml new file +17 -0

+
+required:
+  - compatible
+
+additionalProperties: false
+
+examples:
+  - |
+    nvmem-layout {
+        compatible = "fixed-layout";
+        #address-cells = <1>;
+        #size-cells = <1>;
+
+        calibration@4000 {
+            reg = <0x4000 0x100>;
+        };
+    };

Documentation/devicetree/bindings/nvmem/layouts/nvmem-layout.yaml +1 -4

index 8512ee538c4c..3b40f7880774 100644
@@ -18,16 +18,13 @@ description: |
   perform their parsing. The nvmem-layout container is here to describe these.
 
 oneOf:
+  - $ref: fixed-layout.yaml
   - $ref: kontron,sl28-vpd.yaml
   - $ref: onie,tlv-layout.yaml
 
 properties:
   compatible: true
 
-  '#address-cells': false
-
-  '#size-cells': false
-
 required:
   - compatible
 

Documentation/devicetree/bindings/nvmem/nvmem.yaml +2 -17

index 75bb93dda9df..b79f1bb795fb 100644
@@ -49,23 +49,8 @@ properties:
 patternProperties:
   "@[0-9a-f]+(,[0-7])?$":
     type: object
-
-    properties:
-      reg:
-        maxItems: 1
-        description:
-          Offset and size in bytes within the storage device.
-
-      bits:
-        $ref: /schemas/types.yaml#/definitions/uint32-array
-        items:
-          - minimum: 0
-            maximum: 7
-            description:
-              Offset in bit within the address range specified by reg.
-          - minimum: 1
-            description:
-              Size in bit within the address range specified by reg.
+    $ref: layouts/fixed-cell.yaml
+    deprecated: true
 
 additionalProperties: true
 

Signature · 1 line

2.34.1

From: Rafał Miłecki <[email protected]>

With support for the "fixed-layout" binding it's possible and preferred now to define fixed NVMEM cells in the layout node. Do that for the example binding.

Signed-off-by Rafał Miłecki <[email protected]>

---
 .../devicetree/bindings/nvmem/nvmem.yaml      | 42 +++++++++++--------
 1 file changed, 24 insertions(+), 18 deletions(-)

From: Rafał Miłecki <[email protected]>

This adds support for the "fixed-layout" NVMEM layout binding. It allows defining NVMEM cells in a layout DT node named "nvmem-layout".

While NVMEM subsystem supports layout drivers it has been discussed that "fixed-layout" may actually be supperted internally. It's because:
1. It's a very basic layout
2. It allows sharing code with legacy syntax parsing
3. It's safer for soc_device_match() due to -EPROBE_DEFER
4. This will make the syntax transition easier

Signed-off-by Rafał Miłecki <[email protected]>

---
 drivers/nvmem/core.c | 32 +++++++++++++++++++++++++++++---
 1 file changed, 29 insertions(+), 3 deletions(-)

drivers/nvmem/core.c +1 -1

index 212c5ba5789f..591b640f53dd 100644
@@ -694,7 +694,7 @@ static int nvmem_validate_keepouts(struct
 nvmem_device *nvmem)
 	return 0;
 }
 
-static int nvmem_add_cells_from_of(struct nvmem_device *nvmem)
+static int nvmem_add_cells_from_dt(struct nvmem_device *nvmem, struct
 device_node *np)
 {

drivers/nvmem/core.c +1 -1

 	struct nvmem_layout *layout = nvmem->layout;
 	struct device *dev = &nvmem->dev;

@@ -702,7 +702,7 @@ static int nvmem_add_cells_from_of(struct
 nvmem_device *nvmem)
 	const __be32 *addr;
 	int len, ret;
 
-	for_each_child_of_node(dev->of_node, child) {
+	for_each_child_of_node(np, child) {
 		struct nvmem_cell_info info = {0};
 

drivers/nvmem/core.c +22 -0

 		addr = of_get_property(child, "reg", &len);

@@ -740,6 +740,28 @@ static int nvmem_add_cells_from_of(struct
 nvmem_device *nvmem)
 	return 0;
 }
 
+static int nvmem_add_cells_from_legacy_of(struct nvmem_device *nvmem)
+{
+	return nvmem_add_cells_from_dt(nvmem, nvmem->dev.of_node);
+}
+
+static int nvmem_add_cells_fixed(struct nvmem_device *nvmem)
+{
+	struct device_node *layout_np;
+	int err = 0;
+
+	layout_np = of_nvmem_layout_get_container(nvmem);
+	if (!layout_np)
+		return 0;
+
+	if (of_device_is_compatible(layout_np, "fixed-layout"))
+		err = nvmem_add_cells_from_dt(nvmem, layout_np);
+
+	of_node_put(layout_np);
+
+	return err;
+}
+
 int __nvmem_layout_register(struct nvmem_layout *layout, struct module 
 *owner)

{

drivers/nvmem/core.c +1 -1

 	layout->owner = owner;

@@ -970,7 +992,7 @@ struct nvmem_device *nvmem_register(const struct
 nvmem_config *config)
 	if (rval)
 		goto err_remove_cells;
 
-	rval = nvmem_add_cells_from_of(nvmem);
+	rval = nvmem_add_cells_from_legacy_of(nvmem);
 	if (rval)
 		goto err_remove_cells;

drivers/nvmem/core.c +3 -0

+	if (rval)
+		goto err_remove_cells;
+
 	rval = nvmem_add_cells_from_layout(nvmem);
 	if (rval)

goto err_remove_cells;