1 /* IBM POWER Barrier Synchronization Register Driver
3 * Copyright IBM Corporation 2008
5 * Author: Sonny Rao <sonnyrao@us.ibm.com>
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 2 of the License, or
10 * (at your option) any later version.
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
17 * You should have received a copy of the GNU General Public License
18 * along with this program; if not, write to the Free Software
19 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
22 #include <linux/kernel.h>
24 #include <linux/of_device.h>
25 #include <linux/of_platform.h>
26 #include <linux/module.h>
27 #include <linux/cdev.h>
28 #include <linux/list.h>
33 This driver exposes a special register which can be used for fast
34 synchronization across a large SMP machine. The hardware is exposed
35 as an array of bytes where each process will write to one of the bytes to
36 indicate it has finished the current stage and this update is broadcast to
37 all processors without having to bounce a cacheline between them. In
38 POWER5 and POWER6 there is one of these registers per SMP, but it is
39 presented in two forms; first, it is given as a whole and then as a number
40 of smaller registers which alias to parts of the single whole register.
41 This can potentially allow multiple groups of processes to each have their
42 own private synchronization device.
44 Note that this hardware *must* be written to using *only* single byte writes.
45 It may be read using 1, 2, 4, or 8 byte loads which must be aligned since
46 this region is treated as cache-inhibited processes should also use a
47 full sync before and after writing to the BSR to ensure all stores and
48 the BSR update have made it to all chips in the system
51 /* This is arbitrary number, up to Power6 it's been 17 or fewer */
52 #define BSR_MAX_DEVS (32)
55 u64 bsr_addr; /* Real address */
56 u64 bsr_len; /* length of mem region we can map */
57 unsigned bsr_bytes; /* size of the BSR reg itself */
58 unsigned bsr_stride; /* interval at which BSR repeats in the page */
59 unsigned bsr_type; /* maps to enum below */
60 unsigned bsr_num; /* bsr id number for its type */
63 struct list_head bsr_list;
67 struct device *bsr_device;
72 static unsigned total_bsr_devs;
73 static struct list_head bsr_devs = LIST_HEAD_INIT(bsr_devs);
74 static struct class *bsr_class;
87 static unsigned bsr_types[BSR_MAX];
90 bsr_size_show(struct device *dev, struct device_attribute *attr, char *buf)
92 struct bsr_dev *bsr_dev = dev_get_drvdata(dev);
93 return sprintf(buf, "%u\n", bsr_dev->bsr_bytes);
97 bsr_stride_show(struct device *dev, struct device_attribute *attr, char *buf)
99 struct bsr_dev *bsr_dev = dev_get_drvdata(dev);
100 return sprintf(buf, "%u\n", bsr_dev->bsr_stride);
104 bsr_len_show(struct device *dev, struct device_attribute *attr, char *buf)
106 struct bsr_dev *bsr_dev = dev_get_drvdata(dev);
107 return sprintf(buf, "%llu\n", bsr_dev->bsr_len);
110 static struct device_attribute bsr_dev_attrs[] = {
111 __ATTR(bsr_size, S_IRUGO, bsr_size_show, NULL),
112 __ATTR(bsr_stride, S_IRUGO, bsr_stride_show, NULL),
113 __ATTR(bsr_length, S_IRUGO, bsr_len_show, NULL),
117 static int bsr_mmap(struct file *filp, struct vm_area_struct *vma)
119 unsigned long size = vma->vm_end - vma->vm_start;
120 struct bsr_dev *dev = filp->private_data;
122 if (size > dev->bsr_len || (size & (PAGE_SIZE-1)))
125 vma->vm_flags |= (VM_IO | VM_DONTEXPAND);
126 vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
128 if (io_remap_pfn_range(vma, vma->vm_start, dev->bsr_addr >> PAGE_SHIFT,
129 size, vma->vm_page_prot))
135 static int bsr_open(struct inode * inode, struct file * filp)
137 struct cdev *cdev = inode->i_cdev;
138 struct bsr_dev *dev = container_of(cdev, struct bsr_dev, bsr_cdev);
140 filp->private_data = dev;
144 static const struct file_operations bsr_fops = {
145 .owner = THIS_MODULE,
150 static void bsr_cleanup_devs(void)
152 struct bsr_dev *cur, *n;
154 list_for_each_entry_safe(cur, n, &bsr_devs, bsr_list) {
155 if (cur->bsr_device) {
156 cdev_del(&cur->bsr_cdev);
157 device_del(cur->bsr_device);
159 list_del(&cur->bsr_list);
164 static int bsr_add_node(struct device_node *bn)
166 int bsr_stride_len, bsr_bytes_len, num_bsr_devs;
167 const u32 *bsr_stride;
168 const u32 *bsr_bytes;
172 bsr_stride = of_get_property(bn, "ibm,lock-stride", &bsr_stride_len);
173 bsr_bytes = of_get_property(bn, "ibm,#lock-bytes", &bsr_bytes_len);
175 if (!bsr_stride || !bsr_bytes ||
176 (bsr_stride_len != bsr_bytes_len)) {
177 printk(KERN_ERR "bsr of-node has missing/incorrect property\n");
181 num_bsr_devs = bsr_bytes_len / sizeof(u32);
183 for (i = 0 ; i < num_bsr_devs; i++) {
184 struct bsr_dev *cur = kzalloc(sizeof(struct bsr_dev),
190 printk(KERN_ERR "Unable to alloc bsr dev\n");
195 result = of_address_to_resource(bn, i, &res);
197 printk(KERN_ERR "bsr of-node has invalid reg property, skipping\n");
202 cur->bsr_minor = i + total_bsr_devs;
203 cur->bsr_addr = res.start;
204 cur->bsr_len = res.end - res.start + 1;
205 cur->bsr_bytes = bsr_bytes[i];
206 cur->bsr_stride = bsr_stride[i];
207 cur->bsr_dev = MKDEV(bsr_major, i + total_bsr_devs);
209 switch(cur->bsr_bytes) {
211 cur->bsr_type = BSR_8;
214 cur->bsr_type = BSR_16;
217 cur->bsr_type = BSR_64;
220 cur->bsr_type = BSR_128;
223 cur->bsr_type = BSR_4096;
226 cur->bsr_type = BSR_UNKNOWN;
229 cur->bsr_num = bsr_types[cur->bsr_type];
230 snprintf(cur->bsr_name, 32, "bsr%d_%d",
231 cur->bsr_bytes, cur->bsr_num);
233 cdev_init(&cur->bsr_cdev, &bsr_fops);
234 result = cdev_add(&cur->bsr_cdev, cur->bsr_dev, 1);
240 cur->bsr_device = device_create(bsr_class, NULL, cur->bsr_dev,
242 if (!cur->bsr_device) {
243 printk(KERN_ERR "device_create failed for %s\n",
245 cdev_del(&cur->bsr_cdev);
250 bsr_types[cur->bsr_type] = cur->bsr_num + 1;
251 list_add_tail(&cur->bsr_list, &bsr_devs);
254 total_bsr_devs += num_bsr_devs;
264 static int bsr_create_devs(struct device_node *bn)
269 ret = bsr_add_node(bn);
274 bn = of_find_compatible_node(bn, NULL, "ibm,bsr");
279 static int __init bsr_init(void)
281 struct device_node *np;
282 dev_t bsr_dev = MKDEV(bsr_major, 0);
286 np = of_find_compatible_node(NULL, NULL, "ibm,bsr");
290 bsr_class = class_create(THIS_MODULE, "bsr");
291 if (IS_ERR(bsr_class)) {
292 printk(KERN_ERR "class_create() failed for bsr_class\n");
295 bsr_class->dev_attrs = bsr_dev_attrs;
297 result = alloc_chrdev_region(&bsr_dev, 0, BSR_MAX_DEVS, "bsr");
298 bsr_major = MAJOR(bsr_dev);
300 printk(KERN_ERR "alloc_chrdev_region() failed for bsr\n");
304 if ((ret = bsr_create_devs(np)) < 0) {
312 unregister_chrdev_region(bsr_dev, BSR_MAX_DEVS);
315 class_destroy(bsr_class);
325 static void __exit bsr_exit(void)
331 class_destroy(bsr_class);
334 unregister_chrdev_region(MKDEV(bsr_major, 0), BSR_MAX_DEVS);
337 module_init(bsr_init);
338 module_exit(bsr_exit);
339 MODULE_LICENSE("GPL");
340 MODULE_AUTHOR("Sonny Rao <sonnyrao@us.ibm.com>");