Power5,Power6 BSR driver

Index: linux-2.6.24/drivers/char/bsr.c
===================================================================
@@ -0,0 +1,307 @@
+/* IBM POWER Barrier Synchronization Register Driver
+ *
+ * Copyright IBM Corporation 2008
+ *
+ * Author: Sonny Rao <[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 option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
+ */
+
+#include <linux/kernel.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/of_platform.h>
+#include <linux/module.h>
+#include <linux/cdev.h>
+#include <linux/list.h>
+#include <linux/mm.h>
+#include <asm/io.h>
+
+/*
+ This driver exposes a special register which can be used for fast
+ synchronization across a large SMP machine.  The hardware is exposed
+ as an array of bytes where each process will write to one of the bytes to
+ indicate it has finished the current stage and this update is broadcast to
+ all processors without having to bounce a cacheline between them. In
+ POWER5 and POWER6 there is one of these registers per SMP,  but it is
+ presented in two forms; first, it is given as a whole and then as a number
+ of smaller registers which alias to parts of the single whole register.
+ This can potentially allow multiple groups of processes to each have their
+ own private synchronization device.
+
+ Note that this hardware *must* be written to using *only* single byte writes.
+ It may be read using 1, 2, 4, or 8 byte loads which must be aligned since
+ this region is treated as cache-inhibited  processes should also use a
+ full sync before and after writing to the BSR to ensure all stores and
+ the BSR update have made it to all chips in the system
+*/
+
+/* This is arbitrary number, up to Power6 it's been 17 or fewer  */
+#define BSR_MAX_DEVS (32)
+
+struct bsr_dev {
+	u64      bsr_addr;     /* Real address */
+	u64      bsr_len;      /* length of mem region we can map */
+	unsigned bsr_bytes;    /* size of the BSR reg itself */
+	unsigned bsr_stride;   /* interval at which BSR repeats in the page */
+	unsigned bsr_type;     /* maps to enum below */
+	unsigned bsr_num;      /* bsr id number for its type */
+	int      bsr_minor;
+
+	dev_t    bsr_dev;
+	struct cdev bsr_cdev;
+	struct device *bsr_device;
+	char     bsr_name[32];
+
+};
+
+static unsigned num_bsr_devs;
+static struct bsr_dev *bsr_devs;
+static struct class *bsr_class;
+static int bsr_major;
+
+enum {
+	BSR_8   = 0,
+	BSR_16  = 1,
+	BSR_64  = 2,
+	BSR_128 = 3,
+	BSR_UNKNOWN = 4,
+	BSR_MAX = 5,
+};
+
+static unsigned bsr_types[BSR_MAX];
+
+static ssize_t
+bsr_size_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct bsr_dev *bsr_dev = dev_get_drvdata(dev);
+	return sprintf(buf, "%u\n", bsr_dev->bsr_bytes);
+}
+
+static ssize_t
+bsr_stride_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct bsr_dev *bsr_dev = dev_get_drvdata(dev);
+	return sprintf(buf, "%u\n", bsr_dev->bsr_stride);
+}
+
+static ssize_t
+bsr_len_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct bsr_dev *bsr_dev = dev_get_drvdata(dev);
+	return sprintf(buf, "%lu\n", bsr_dev->bsr_len);
+}
+
+static struct device_attribute bsr_dev_attrs[] = {
+	__ATTR(bsr_size, S_IRUGO, bsr_size_show, NULL),
+	__ATTR(bsr_stride, S_IRUGO, bsr_stride_show, NULL),
+	__ATTR(bsr_length, S_IRUGO, bsr_len_show, NULL),
+	__ATTR_NULL
+};
+
+static int bsr_mmap(struct file *filp, struct vm_area_struct *vma)
+{
+	unsigned long size   = vma->vm_end - vma->vm_start;
+	struct bsr_dev *dev = filp->private_data;
+
+	if (size > dev->bsr_len || (size & (PAGE_SIZE-1)))
+		return -EINVAL;
+
+	vma->vm_flags |= (VM_IO | VM_DONTEXPAND);
+	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+
+	if (io_remap_pfn_range(vma, vma->vm_start, dev->bsr_addr >> PAGE_SHIFT,
+			       size, vma->vm_page_prot))
+	    return -EAGAIN;
+
+	return 0;
+}
+
+static int bsr_open(struct inode * inode, struct file * filp)
+{
+	struct cdev *cdev = inode->i_cdev;
+	struct bsr_dev *dev = container_of(cdev, struct bsr_dev, bsr_cdev);
+
+	filp->private_data = dev;
+	return 0;
+}
+
+const static struct file_operations bsr_fops = {
+	.owner = THIS_MODULE,
+	.mmap  = bsr_mmap,
+	.open  = bsr_open,
+};
+
+static void bsr_cleanup_devs(void)
+{
+	int i;
+	for (i=0 ; i < num_bsr_devs; i++) {
+		struct bsr_dev *cur = bsr_devs + i;
+		if (cur->bsr_device) {
+			cdev_del(&cur->bsr_cdev);
+			device_del(cur->bsr_device);
+		}
+	}
+
+	kfree(bsr_devs);
+}
+
+static int bsr_create_devs(struct device_node *bn)
+{
+	int reg_len, bsr_stride_len, bsr_bytes_len;
+	const u64 *reg;
+	const u32 *bsr_stride;
+	const u32 *bsr_bytes;
+	unsigned i;
+
+	reg        = of_get_property(bn, "reg", &reg_len);
+	bsr_stride = of_get_property(bn, "ibm,lock-stride", &bsr_stride_len);
+	bsr_bytes  = of_get_property(bn, "ibm,#lock-bytes", &bsr_bytes_len);
+
+	if (!reg || !bsr_stride || !bsr_bytes ||
+	    (bsr_stride_len != bsr_bytes_len) ||
+	    (bsr_stride_len/4 != reg_len/16)) {
+		printk(KERN_ERR "bsr of-node has missing/incorrect property\n");
+		return -ENODEV;
+	}
+
+	num_bsr_devs = reg_len/16;
+
+	/* only a warning, its informational since we'll fail and exit */
+	WARN_ON(num_bsr_devs > BSR_MAX_DEVS);
+
+	bsr_devs = kzalloc(sizeof(struct bsr_dev) * num_bsr_devs, GFP_KERNEL);
+	if (!bsr_devs)
+		return -ENOMEM;
+
+	for (i=0 ; i < num_bsr_devs; i++) {
+		struct bsr_dev *cur = bsr_devs + i;
+		int result;
+
+		cur->bsr_minor  = i;
+		cur->bsr_addr   = reg[i*2];
+		cur->bsr_len    = reg[i*2 + 1];
+		cur->bsr_bytes  = bsr_bytes[i];
+		cur->bsr_stride = bsr_stride[i];
+		cur->bsr_dev    = MKDEV(bsr_major, i);
+
+		switch(cur->bsr_bytes) {
+		case 8:
+			cur->bsr_type = BSR_8;
+			break;
+		case 16:
+			cur->bsr_type = BSR_16;
+			break;
+		case 64:
+			cur->bsr_type = BSR_64;
+			break;
+		case 128:
+			cur->bsr_type = BSR_128;
+			break;
+		default:
+			cur->bsr_type = BSR_UNKNOWN;
+			printk(KERN_INFO "unknown BSR size %d\n",cur->bsr_bytes);
+		}
+
+		cur->bsr_num = bsr_types[cur->bsr_type];
+		bsr_types[cur->bsr_type] = cur->bsr_num + 1;
+		snprintf(cur->bsr_name, 32, "bsr%d_%d",
+			 cur->bsr_bytes, cur->bsr_num);
+
+		cdev_init(&cur->bsr_cdev, &bsr_fops);
+		result = cdev_add(&cur->bsr_cdev, cur->bsr_dev, 1);
+		if (result)
+			goto out_err;
+
+		cur->bsr_device = device_create(bsr_class, NULL,
+						cur->bsr_dev,
+						cur->bsr_name);
+		if (!cur->bsr_device) {
+			printk(KERN_ERR "device_create failed for %s\n",
+			       cur->bsr_name);
+			cdev_del(&cur->bsr_cdev);
+			goto out_err;
+		}
+		dev_set_drvdata(cur->bsr_device, cur);
+	}
+
+	return 0;
+
+ out_err:
+
+	bsr_cleanup_devs();
+	return -ENODEV;
+}
+
+static int __init bsr_init(void)
+{
+	struct device_node *np;
+	dev_t bsr_dev = MKDEV(bsr_major, 0);
+	int ret = -ENODEV;
+	int result;
+
+	np = of_find_compatible_node(NULL, "ibm,bsr", "ibm,bsr");
+	if (!np)
+		goto out_err;
+
+	bsr_class = class_create(THIS_MODULE, "bsr");
+	if (IS_ERR(bsr_class)) {
+		printk(KERN_ERR "class_create() failed for bsr_class\n");
+		goto out_err;
+	}
+	bsr_class->dev_attrs = bsr_dev_attrs;
+
+	result = alloc_chrdev_region(&bsr_dev, 0, BSR_MAX_DEVS, "bsr");
+	bsr_major = MAJOR(bsr_dev);
+	if (result < 0) {
+		printk(KERN_ERR "alloc_chrdev_region() failed for bsr\n");
+		goto out_err_1;
+	}
+
+	if ((ret = bsr_create_devs(np)) < 0)
+		goto out_err_2;
+
+	of_node_put(np);
+
+	return 0;
+
+ out_err_2:
+	unregister_chrdev_region(bsr_dev, BSR_MAX_DEVS);
+
+ out_err_1:
+	class_destroy(bsr_class);
+	of_node_put(np);
+
+ out_err:
+
+	return ret;
+}
+
+static void __exit  bsr_exit(void)
+{
+
+	bsr_cleanup_devs();
+
+	if (bsr_class)
+		class_destroy(bsr_class);
+
+	if (bsr_major)
+		unregister_chrdev_region(MKDEV(bsr_major, 0), BSR_MAX_DEVS);
+}
+
+module_init(bsr_init);
+module_exit(bsr_exit);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Sonny Rao <[email protected]>");

Index: linux-2.6.24/drivers/char/bsr.c
===================================================================
@@ -0,0 +1,309 @@
+/* IBM POWER Barrier Synchronization Register Driver
+ *
+ * Copyright IBM Corporation 2008
+ *
+ * Author: Sonny Rao <[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 option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
+ */
+
+#include <linux/kernel.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/of_platform.h>
+#include <linux/module.h>
+#include <linux/cdev.h>
+#include <linux/list.h>
+#include <linux/mm.h>
+#include <asm/io.h>
+
+/*
+ This driver exposes a special register which can be used for fast
+ synchronization across a large SMP machine.  The hardware is exposed
+ as an array of bytes where each process will write to one of the bytes to
+ indicate it has finished the current stage and this update is broadcast to
+ all processors without having to bounce a cacheline between them. In
+ POWER5 and POWER6 there is one of these registers per SMP,  but it is
+ presented in two forms; first, it is given as a whole and then as a number
+ of smaller registers which alias to parts of the single whole register.
+ This can potentially allow multiple groups of processes to each have their
+ own private synchronization device.
+
+ Note that this hardware *must* be written to using *only* single byte writes.
+ It may be read using 1, 2, 4, or 8 byte loads which must be aligned since
+ this region is treated as cache-inhibited  processes should also use a
+ full sync before and after writing to the BSR to ensure all stores and
+ the BSR update have made it to all chips in the system
+*/
+
+/* This is arbitrary number, up to Power6 it's been 17 or fewer  */
+#define BSR_MAX_DEVS (32)
+
+struct bsr_dev {
+	u64      bsr_addr;     /* Real address */
+	u64      bsr_len;      /* length of mem region we can map */
+	unsigned bsr_bytes;    /* size of the BSR reg itself */
+	unsigned bsr_stride;   /* interval at which BSR repeats in the page */
+	unsigned bsr_type;     /* maps to enum below */
+	unsigned bsr_num;      /* bsr id number for its type */
+	int      bsr_minor;
+
+	dev_t    bsr_dev;
+	struct cdev bsr_cdev;
+	struct device *bsr_device;
+	char     bsr_name[32];
+
+};
+
+static unsigned num_bsr_devs;
+static struct bsr_dev *bsr_devs;
+static struct class *bsr_class;
+static int bsr_major;
+
+enum {
+	BSR_8   = 0,
+	BSR_16  = 1,
+	BSR_64  = 2,
+	BSR_128 = 3,
+	BSR_UNKNOWN = 4,
+	BSR_MAX = 5,
+};
+
+static unsigned bsr_types[BSR_MAX];
+
+static ssize_t
+bsr_size_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct bsr_dev *bsr_dev = dev_get_drvdata(dev);
+	return sprintf(buf, "%u\n", bsr_dev->bsr_bytes);
+}
+
+static ssize_t
+bsr_stride_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct bsr_dev *bsr_dev = dev_get_drvdata(dev);
+	return sprintf(buf, "%u\n", bsr_dev->bsr_stride);
+}
+
+static ssize_t
+bsr_len_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct bsr_dev *bsr_dev = dev_get_drvdata(dev);
+	return sprintf(buf, "%lu\n", bsr_dev->bsr_len);
+}
+
+static struct device_attribute bsr_dev_attrs[] = {
+	__ATTR(bsr_size, S_IRUGO, bsr_size_show, NULL),
+	__ATTR(bsr_stride, S_IRUGO, bsr_stride_show, NULL),
+	__ATTR(bsr_length, S_IRUGO, bsr_len_show, NULL),
+	__ATTR_NULL
+};
+
+static int bsr_mmap(struct file *filp, struct vm_area_struct *vma)
+{
+	unsigned long size   = vma->vm_end - vma->vm_start;
+	struct bsr_dev *dev = filp->private_data;
+
+	if (size > dev->bsr_len || (size & (PAGE_SIZE-1)))
+		return -EINVAL;
+
+	vma->vm_flags |= (VM_IO | VM_DONTEXPAND);
+	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+
+	if (io_remap_pfn_range(vma, vma->vm_start, dev->bsr_addr >> PAGE_SHIFT,
+			       size, vma->vm_page_prot))
+		return -EAGAIN;
+
+	return 0;
+}
+
+static int bsr_open(struct inode * inode, struct file * filp)
+{
+	struct cdev *cdev = inode->i_cdev;
+	struct bsr_dev *dev = container_of(cdev, struct bsr_dev, bsr_cdev);
+
+	filp->private_data = dev;
+	return 0;
+}
+
+const static struct file_operations bsr_fops = {
+	.owner = THIS_MODULE,
+	.mmap  = bsr_mmap,
+	.open  = bsr_open,
+};
+
+static void bsr_cleanup_devs(void)
+{
+	int i;
+	for (i=0 ; i < num_bsr_devs; i++) {
+		struct bsr_dev *cur = bsr_devs + i;
+		if (cur->bsr_device) {
+			cdev_del(&cur->bsr_cdev);
+			device_del(cur->bsr_device);
+		}
+	}
+
+	kfree(bsr_devs);
+}
+
+static int bsr_create_devs(struct device_node *bn)
+{
+	int reg_len, bsr_stride_len, bsr_bytes_len;
+	const u64 *reg;
+	const u32 *bsr_stride;
+	const u32 *bsr_bytes;
+	unsigned i;
+
+	reg        = of_get_property(bn, "reg", &reg_len);
+	bsr_stride = of_get_property(bn, "ibm,lock-stride", &bsr_stride_len);
+	bsr_bytes  = of_get_property(bn, "ibm,#lock-bytes", &bsr_bytes_len);
+
+	if (!reg || !bsr_stride || !bsr_bytes ||
+	    (bsr_stride_len != bsr_bytes_len) ||
+	    (bsr_stride_len / 4 != reg_len / 16)) {
+		printk(KERN_ERR "bsr of-node has missing/incorrect property\n");
+		return -ENODEV;
+	}
+
+	num_bsr_devs = reg_len / 16;
+
+	/* only a warning, its informational since we'll fail and exit */
+	WARN_ON(num_bsr_devs > BSR_MAX_DEVS);
+
+	bsr_devs = kzalloc(sizeof(struct bsr_dev) * num_bsr_devs, GFP_KERNEL);
+	if (!bsr_devs)
+		return -ENOMEM;
+
+	for (i = 0 ; i < num_bsr_devs; i++) {
+		struct bsr_dev *cur = bsr_devs + i;
+		int result;
+
+		cur->bsr_minor  = i;
+		cur->bsr_addr   = reg[i * 2];
+		cur->bsr_len    = reg[i * 2 + 1];
+		cur->bsr_bytes  = bsr_bytes[i];
+		cur->bsr_stride = bsr_stride[i];
+		cur->bsr_dev    = MKDEV(bsr_major, i);
+
+		switch(cur->bsr_bytes) {
+		case 8:
+			cur->bsr_type = BSR_8;
+			break;
+		case 16:
+			cur->bsr_type = BSR_16;
+			break;
+		case 64:
+			cur->bsr_type = BSR_64;
+			break;
+		case 128:
+			cur->bsr_type = BSR_128;
+			break;
+		default:
+			cur->bsr_type = BSR_UNKNOWN;
+			printk(KERN_INFO "unknown BSR size %d\n",cur->bsr_bytes);
+		}
+
+		cur->bsr_num = bsr_types[cur->bsr_type];
+		bsr_types[cur->bsr_type] = cur->bsr_num + 1;
+		snprintf(cur->bsr_name, 32, "bsr%d_%d",
+			 cur->bsr_bytes, cur->bsr_num);
+
+		cdev_init(&cur->bsr_cdev, &bsr_fops);
+		result = cdev_add(&cur->bsr_cdev, cur->bsr_dev, 1);
+		if (result)
+			goto out_err;
+
+		cur->bsr_device = device_create(bsr_class, NULL,
+						cur->bsr_dev,
+						cur->bsr_name);
+		if (!cur->bsr_device) {
+			printk(KERN_ERR "device_create failed for %s\n",
+			       cur->bsr_name);
+			cdev_del(&cur->bsr_cdev);
+			goto out_err;
+		}
+		dev_set_drvdata(cur->bsr_device, cur);
+	}
+
+	return 0;
+
+ out_err:
+
+	bsr_cleanup_devs();
+	return -ENODEV;
+}
+
+static int __init bsr_init(void)
+{
+	struct device_node *np;
+	dev_t bsr_dev = MKDEV(bsr_major, 0);
+	int ret = -ENODEV;
+	int result;
+
+	np = of_find_compatible_node(NULL, "ibm,bsr", "ibm,bsr");
+	if (!np)
+		goto out_err;
+
+	bsr_class = class_create(THIS_MODULE, "bsr");
+	if (IS_ERR(bsr_class)) {
+		printk(KERN_ERR "class_create() failed for bsr_class\n");
+		goto out_err_1;
+	}
+	bsr_class->dev_attrs = bsr_dev_attrs;
+
+	result = alloc_chrdev_region(&bsr_dev, 0, BSR_MAX_DEVS, "bsr");
+	bsr_major = MAJOR(bsr_dev);
+	if (result < 0) {
+		printk(KERN_ERR "alloc_chrdev_region() failed for bsr\n");
+		goto out_err_2;
+	}
+
+	if ((ret = bsr_create_devs(np)) < 0)
+		goto out_err_3;
+
+	of_node_put(np);
+
+	return 0;
+
+ out_err_3:
+	unregister_chrdev_region(bsr_dev, BSR_MAX_DEVS);
+
+ out_err_2:
+	class_destroy(bsr_class);
+
+ out_err_1:
+	of_node_put(np);
+
+ out_err:
+
+	return ret;
+}
+
+static void __exit  bsr_exit(void)
+{
+
+	bsr_cleanup_devs();
+
+	if (bsr_class)
+		class_destroy(bsr_class);
+
+	if (bsr_major)
+		unregister_chrdev_region(MKDEV(bsr_major, 0), BSR_MAX_DEVS);
+}
+
+module_init(bsr_init);
+module_exit(bsr_exit);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Sonny Rao <[email protected]>");

Index: linux-dev/drivers/char/bsr.c
===================================================================
@@ -0,0 +1,313 @@
+/* IBM POWER Barrier Synchronization Register Driver
+ *
+ * Copyright IBM Corporation 2008
+ *
+ * Author: Sonny Rao <[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 option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
+ */
+
+#include <linux/kernel.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/of_platform.h>
+#include <linux/module.h>
+#include <linux/cdev.h>
+#include <linux/list.h>
+#include <linux/mm.h>
+#include <asm/io.h>
+
+/*
+ This driver exposes a special register which can be used for fast
+ synchronization across a large SMP machine.  The hardware is exposed
+ as an array of bytes where each process will write to one of the bytes to
+ indicate it has finished the current stage and this update is broadcast to
+ all processors without having to bounce a cacheline between them. In
+ POWER5 and POWER6 there is one of these registers per SMP,  but it is
+ presented in two forms; first, it is given as a whole and then as a number
+ of smaller registers which alias to parts of the single whole register.
+ This can potentially allow multiple groups of processes to each have their
+ own private synchronization device.
+
+ Note that this hardware *must* be written to using *only* single byte writes.
+ It may be read using 1, 2, 4, or 8 byte loads which must be aligned since
+ this region is treated as cache-inhibited  processes should also use a
+ full sync before and after writing to the BSR to ensure all stores and
+ the BSR update have made it to all chips in the system
+*/
+
+/* This is arbitrary number, up to Power6 it's been 17 or fewer  */
+#define BSR_MAX_DEVS (32)
+
+struct bsr_dev {
+	u64      bsr_addr;     /* Real address */
+	u64      bsr_len;      /* length of mem region we can map */
+	unsigned bsr_bytes;    /* size of the BSR reg itself */
+	unsigned bsr_stride;   /* interval at which BSR repeats in the page */
+	unsigned bsr_type;     /* maps to enum below */
+	unsigned bsr_num;      /* bsr id number for its type */
+	int      bsr_minor;
+
+	dev_t    bsr_dev;
+	struct cdev bsr_cdev;
+	struct device *bsr_device;
+	char     bsr_name[32];
+
+};
+
+static unsigned num_bsr_devs;
+static struct bsr_dev *bsr_devs;
+static struct class *bsr_class;
+static int bsr_major;
+
+enum {
+	BSR_8   = 0,
+	BSR_16  = 1,
+	BSR_64  = 2,
+	BSR_128 = 3,
+	BSR_UNKNOWN = 4,
+	BSR_MAX = 5,
+};
+
+static unsigned bsr_types[BSR_MAX];
+
+static ssize_t
+bsr_size_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct bsr_dev *bsr_dev = dev_get_drvdata(dev);
+	return sprintf(buf, "%u\n", bsr_dev->bsr_bytes);
+}
+
+static ssize_t
+bsr_stride_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct bsr_dev *bsr_dev = dev_get_drvdata(dev);
+	return sprintf(buf, "%u\n", bsr_dev->bsr_stride);
+}
+
+static ssize_t
+bsr_len_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct bsr_dev *bsr_dev = dev_get_drvdata(dev);
+	return sprintf(buf, "%lu\n", bsr_dev->bsr_len);
+}
+
+static struct device_attribute bsr_dev_attrs[] = {
+	__ATTR(bsr_size, S_IRUGO, bsr_size_show, NULL),
+	__ATTR(bsr_stride, S_IRUGO, bsr_stride_show, NULL),
+	__ATTR(bsr_length, S_IRUGO, bsr_len_show, NULL),
+	__ATTR_NULL
+};
+
+static int bsr_mmap(struct file *filp, struct vm_area_struct *vma)
+{
+	unsigned long size   = vma->vm_end - vma->vm_start;
+	struct bsr_dev *dev = filp->private_data;
+
+	if (size > dev->bsr_len || (size & (PAGE_SIZE-1)))
+		return -EINVAL;
+
+	vma->vm_flags |= (VM_IO | VM_DONTEXPAND);
+	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+
+	if (io_remap_pfn_range(vma, vma->vm_start, dev->bsr_addr >> PAGE_SHIFT,
+			       size, vma->vm_page_prot))
+		return -EAGAIN;
+
+	return 0;
+}
+
+static int bsr_open(struct inode * inode, struct file * filp)
+{
+	struct cdev *cdev = inode->i_cdev;
+	struct bsr_dev *dev = container_of(cdev, struct bsr_dev, bsr_cdev);
+
+	filp->private_data = dev;
+	return 0;
+}
+
+const static struct file_operations bsr_fops = {
+	.owner = THIS_MODULE,
+	.mmap  = bsr_mmap,
+	.open  = bsr_open,
+};
+
+static void bsr_cleanup_devs(void)
+{
+	int i;
+	for (i=0 ; i < num_bsr_devs; i++) {
+		struct bsr_dev *cur = bsr_devs + i;
+		if (cur->bsr_device) {
+			cdev_del(&cur->bsr_cdev);
+			device_del(cur->bsr_device);
+		}
+	}
+
+	kfree(bsr_devs);
+}
+
+static int bsr_create_devs(struct device_node *bn)
+{
+	int bsr_stride_len, bsr_bytes_len;
+	const u32 *bsr_stride;
+	const u32 *bsr_bytes;
+	unsigned i;
+
+	bsr_stride = of_get_property(bn, "ibm,lock-stride", &bsr_stride_len);
+	bsr_bytes  = of_get_property(bn, "ibm,#lock-bytes", &bsr_bytes_len);
+
+	if (!bsr_stride || !bsr_bytes ||
+	    (bsr_stride_len != bsr_bytes_len)) {
+		printk(KERN_ERR "bsr of-node has missing/incorrect property\n");
+		return -ENODEV;
+	}
+
+	num_bsr_devs = bsr_bytes_len / sizeof(u32);
+
+	/* only a warning, its informational since we'll fail and exit */
+	WARN_ON(num_bsr_devs > BSR_MAX_DEVS);
+
+	bsr_devs = kzalloc(sizeof(struct bsr_dev) * num_bsr_devs, GFP_KERNEL);
+	if (!bsr_devs)
+		return -ENOMEM;
+
+	for (i = 0 ; i < num_bsr_devs; i++) {
+		struct bsr_dev *cur = bsr_devs + i;
+		struct resource res;
+		int result;
+
+		result = of_address_to_resource(bn, i, &res);
+		if (result < 0) {
+			printk(KERN_ERR "bsr of-node has invalid reg property\n");
+			goto out_err;
+		}
+
+		cur->bsr_minor  = i;
+		cur->bsr_addr   = res.start;
+		cur->bsr_len    = res.end - res.start + 1;
+		cur->bsr_bytes  = bsr_bytes[i];
+		cur->bsr_stride = bsr_stride[i];
+		cur->bsr_dev    = MKDEV(bsr_major, i);
+
+		switch(cur->bsr_bytes) {
+		case 8:
+			cur->bsr_type = BSR_8;
+			break;
+		case 16:
+			cur->bsr_type = BSR_16;
+			break;
+		case 64:
+			cur->bsr_type = BSR_64;
+			break;
+		case 128:
+			cur->bsr_type = BSR_128;
+			break;
+		default:
+			cur->bsr_type = BSR_UNKNOWN;
+			printk(KERN_INFO "unknown BSR size %d\n",cur->bsr_bytes);
+		}
+
+		cur->bsr_num = bsr_types[cur->bsr_type];
+		bsr_types[cur->bsr_type] = cur->bsr_num + 1;
+		snprintf(cur->bsr_name, 32, "bsr%d_%d",
+			 cur->bsr_bytes, cur->bsr_num);
+
+		cdev_init(&cur->bsr_cdev, &bsr_fops);
+		result = cdev_add(&cur->bsr_cdev, cur->bsr_dev, 1);
+		if (result)
+			goto out_err;
+
+		cur->bsr_device = device_create(bsr_class, NULL,
+						cur->bsr_dev,
+						cur->bsr_name);
+		if (!cur->bsr_device) {
+			printk(KERN_ERR "device_create failed for %s\n",
+			       cur->bsr_name);
+			cdev_del(&cur->bsr_cdev);
+			goto out_err;
+		}
+		dev_set_drvdata(cur->bsr_device, cur);
+	}
+
+	return 0;
+
+ out_err:
+
+	bsr_cleanup_devs();
+	return -ENODEV;
+}
+
+static int __init bsr_init(void)
+{
+	struct device_node *np;
+	dev_t bsr_dev = MKDEV(bsr_major, 0);
+	int ret = -ENODEV;
+	int result;
+
+	np = of_find_compatible_node(NULL, "ibm,bsr", "ibm,bsr");
+	if (!np)
+		goto out_err;
+
+	bsr_class = class_create(THIS_MODULE, "bsr");
+	if (IS_ERR(bsr_class)) {
+		printk(KERN_ERR "class_create() failed for bsr_class\n");
+		goto out_err_1;
+	}
+	bsr_class->dev_attrs = bsr_dev_attrs;
+
+	result = alloc_chrdev_region(&bsr_dev, 0, BSR_MAX_DEVS, "bsr");
+	bsr_major = MAJOR(bsr_dev);
+	if (result < 0) {
+		printk(KERN_ERR "alloc_chrdev_region() failed for bsr\n");
+		goto out_err_2;
+	}
+
+	if ((ret = bsr_create_devs(np)) < 0)
+		goto out_err_3;
+
+	of_node_put(np);
+
+	return 0;
+
+ out_err_3:
+	unregister_chrdev_region(bsr_dev, BSR_MAX_DEVS);
+
+ out_err_2:
+	class_destroy(bsr_class);
+
+ out_err_1:
+	of_node_put(np);
+
+ out_err:
+
+	return ret;
+}
+
+static void __exit  bsr_exit(void)
+{
+
+	bsr_cleanup_devs();
+
+	if (bsr_class)
+		class_destroy(bsr_class);
+
+	if (bsr_major)
+		unregister_chrdev_region(MKDEV(bsr_major, 0), BSR_MAX_DEVS);
+}
+
+module_init(bsr_init);
+module_exit(bsr_exit);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Sonny Rao <[email protected]>");

Index: linux-dev/drivers/char/bsr.c
===================================================================
@@ -0,0 +1,312 @@
+/* IBM POWER Barrier Synchronization Register Driver
+ *
+ * Copyright IBM Corporation 2008
+ *
+ * Author: Sonny Rao <[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 option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
+ */
+
+#include <linux/kernel.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/of_platform.h>
+#include <linux/module.h>
+#include <linux/cdev.h>
+#include <linux/list.h>
+#include <linux/mm.h>
+#include <asm/io.h>
+
+/*
+ This driver exposes a special register which can be used for fast
+ synchronization across a large SMP machine.  The hardware is exposed
+ as an array of bytes where each process will write to one of the bytes to
+ indicate it has finished the current stage and this update is broadcast to
+ all processors without having to bounce a cacheline between them. In
+ POWER5 and POWER6 there is one of these registers per SMP,  but it is
+ presented in two forms; first, it is given as a whole and then as a number
+ of smaller registers which alias to parts of the single whole register.
+ This can potentially allow multiple groups of processes to each have their
+ own private synchronization device.
+
+ Note that this hardware *must* be written to using *only* single byte writes.
+ It may be read using 1, 2, 4, or 8 byte loads which must be aligned since
+ this region is treated as cache-inhibited  processes should also use a
+ full sync before and after writing to the BSR to ensure all stores and
+ the BSR update have made it to all chips in the system
+*/
+
+/* This is arbitrary number, up to Power6 it's been 17 or fewer  */
+#define BSR_MAX_DEVS (32)
+
+struct bsr_dev {
+	u64      bsr_addr;     /* Real address */
+	u64      bsr_len;      /* length of mem region we can map */
+	unsigned bsr_bytes;    /* size of the BSR reg itself */
+	unsigned bsr_stride;   /* interval at which BSR repeats in the page */
+	unsigned bsr_type;     /* maps to enum below */
+	unsigned bsr_num;      /* bsr id number for its type */
+	int      bsr_minor;
+
+	dev_t    bsr_dev;
+	struct cdev bsr_cdev;
+	struct device *bsr_device;
+	char     bsr_name[32];
+
+};
+
+static unsigned num_bsr_devs;
+static struct bsr_dev *bsr_devs;
+static struct class *bsr_class;
+static int bsr_major;
+
+enum {
+	BSR_8   = 0,
+	BSR_16  = 1,
+	BSR_64  = 2,
+	BSR_128 = 3,
+	BSR_UNKNOWN = 4,
+	BSR_MAX = 5,
+};
+
+static unsigned bsr_types[BSR_MAX];
+
+static ssize_t
+bsr_size_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct bsr_dev *bsr_dev = dev_get_drvdata(dev);
+	return sprintf(buf, "%u\n", bsr_dev->bsr_bytes);
+}
+
+static ssize_t
+bsr_stride_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct bsr_dev *bsr_dev = dev_get_drvdata(dev);
+	return sprintf(buf, "%u\n", bsr_dev->bsr_stride);
+}
+
+static ssize_t
+bsr_len_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct bsr_dev *bsr_dev = dev_get_drvdata(dev);
+	return sprintf(buf, "%lu\n", bsr_dev->bsr_len);
+}
+
+static struct device_attribute bsr_dev_attrs[] = {
+	__ATTR(bsr_size, S_IRUGO, bsr_size_show, NULL),
+	__ATTR(bsr_stride, S_IRUGO, bsr_stride_show, NULL),
+	__ATTR(bsr_length, S_IRUGO, bsr_len_show, NULL),
+	__ATTR_NULL
+};
+
+static int bsr_mmap(struct file *filp, struct vm_area_struct *vma)
+{
+	unsigned long size   = vma->vm_end - vma->vm_start;
+	struct bsr_dev *dev = filp->private_data;
+
+	if (size > dev->bsr_len || (size & (PAGE_SIZE-1)))
+		return -EINVAL;
+
+	vma->vm_flags |= (VM_IO | VM_DONTEXPAND);
+	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+
+	if (io_remap_pfn_range(vma, vma->vm_start, dev->bsr_addr >> PAGE_SHIFT,
+			       size, vma->vm_page_prot))
+		return -EAGAIN;
+
+	return 0;
+}
+
+static int bsr_open(struct inode * inode, struct file * filp)
+{
+	struct cdev *cdev = inode->i_cdev;
+	struct bsr_dev *dev = container_of(cdev, struct bsr_dev, bsr_cdev);
+
+	filp->private_data = dev;
+	return 0;
+}
+
+const static struct file_operations bsr_fops = {
+	.owner = THIS_MODULE,
+	.mmap  = bsr_mmap,
+	.open  = bsr_open,
+};
+
+static void bsr_cleanup_devs(void)
+{
+	int i;
+	for (i=0 ; i < num_bsr_devs; i++) {
+		struct bsr_dev *cur = bsr_devs + i;
+		if (cur->bsr_device) {
+			cdev_del(&cur->bsr_cdev);
+			device_del(cur->bsr_device);
+		}
+	}
+
+	kfree(bsr_devs);
+}
+
+static int bsr_create_devs(struct device_node *bn)
+{
+	int bsr_stride_len, bsr_bytes_len;
+	const u32 *bsr_stride;
+	const u32 *bsr_bytes;
+	unsigned i;
+
+	bsr_stride = of_get_property(bn, "ibm,lock-stride", &bsr_stride_len);
+	bsr_bytes  = of_get_property(bn, "ibm,#lock-bytes", &bsr_bytes_len);
+
+	if (!bsr_stride || !bsr_bytes ||
+	    (bsr_stride_len != bsr_bytes_len)) {
+		printk(KERN_ERR "bsr of-node has missing/incorrect property\n");
+		return -ENODEV;
+	}
+
+	num_bsr_devs = bsr_bytes_len / sizeof(u32);
+
+	/* only a warning, its informational since we'll fail and exit */
+	WARN_ON(num_bsr_devs > BSR_MAX_DEVS);
+
+	bsr_devs = kzalloc(sizeof(struct bsr_dev) * num_bsr_devs, GFP_KERNEL);
+	if (!bsr_devs)
+		return -ENOMEM;
+
+	for (i = 0 ; i < num_bsr_devs; i++) {
+		struct bsr_dev *cur = bsr_devs + i;
+		struct resource res;
+		int result;
+
+		result = of_address_to_resource(bn, i, &res);
+		if (result < 0) {
+			printk(KERN_ERR "bsr of-node has invalid reg property\n");
+			goto out_err;
+		}
+
+		cur->bsr_minor  = i;
+		cur->bsr_addr   = res.start;
+		cur->bsr_len    = res.end - res.start + 1;
+		cur->bsr_bytes  = bsr_bytes[i];
+		cur->bsr_stride = bsr_stride[i];
+		cur->bsr_dev    = MKDEV(bsr_major, i);
+
+		switch(cur->bsr_bytes) {
+		case 8:
+			cur->bsr_type = BSR_8;
+			break;
+		case 16:
+			cur->bsr_type = BSR_16;
+			break;
+		case 64:
+			cur->bsr_type = BSR_64;
+			break;
+		case 128:
+			cur->bsr_type = BSR_128;
+			break;
+		default:
+			cur->bsr_type = BSR_UNKNOWN;
+			printk(KERN_INFO "unknown BSR size %d\n",cur->bsr_bytes);
+		}
+
+		cur->bsr_num = bsr_types[cur->bsr_type];
+		bsr_types[cur->bsr_type] = cur->bsr_num + 1;
+		snprintf(cur->bsr_name, 32, "bsr%d_%d",
+			 cur->bsr_bytes, cur->bsr_num);
+
+		cdev_init(&cur->bsr_cdev, &bsr_fops);
+		result = cdev_add(&cur->bsr_cdev, cur->bsr_dev, 1);
+		if (result)
+			goto out_err;
+
+		cur->bsr_device = device_create_drvdata(bsr_class, NULL,
+							cur->bsr_dev,
+							cur, cur->bsr_name);
+		if (!cur->bsr_device) {
+			printk(KERN_ERR "device_create failed for %s\n",
+			       cur->bsr_name);
+			cdev_del(&cur->bsr_cdev);
+			goto out_err;
+		}
+	}
+
+	return 0;
+
+ out_err:
+
+	bsr_cleanup_devs();
+	return -ENODEV;
+}
+
+static int __init bsr_init(void)
+{
+	struct device_node *np;
+	dev_t bsr_dev = MKDEV(bsr_major, 0);
+	int ret = -ENODEV;
+	int result;
+
+	np = of_find_compatible_node(NULL, "ibm,bsr", "ibm,bsr");
+	if (!np)
+		goto out_err;
+
+	bsr_class = class_create(THIS_MODULE, "bsr");
+	if (IS_ERR(bsr_class)) {
+		printk(KERN_ERR "class_create() failed for bsr_class\n");
+		goto out_err_1;
+	}
+	bsr_class->dev_attrs = bsr_dev_attrs;
+
+	result = alloc_chrdev_region(&bsr_dev, 0, BSR_MAX_DEVS, "bsr");
+	bsr_major = MAJOR(bsr_dev);
+	if (result < 0) {
+		printk(KERN_ERR "alloc_chrdev_region() failed for bsr\n");
+		goto out_err_2;
+	}
+
+	if ((ret = bsr_create_devs(np)) < 0)
+		goto out_err_3;
+
+	of_node_put(np);
+
+	return 0;
+
+ out_err_3:
+	unregister_chrdev_region(bsr_dev, BSR_MAX_DEVS);
+
+ out_err_2:
+	class_destroy(bsr_class);
+
+ out_err_1:
+	of_node_put(np);
+
+ out_err:
+
+	return ret;
+}
+
+static void __exit  bsr_exit(void)
+{
+
+	bsr_cleanup_devs();
+
+	if (bsr_class)
+		class_destroy(bsr_class);
+
+	if (bsr_major)
+		unregister_chrdev_region(MKDEV(bsr_major, 0), BSR_MAX_DEVS);
+}
+
+module_init(bsr_init);
+module_exit(bsr_exit);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Sonny Rao <[email protected]>");