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;
86 static unsigned bsr_types[BSR_MAX];
89 bsr_size_show(struct device *dev, struct device_attribute *attr, char *buf)
91 struct bsr_dev *bsr_dev = dev_get_drvdata(dev);
92 return sprintf(buf, "%u\n", bsr_dev->bsr_bytes);
96 bsr_stride_show(struct device *dev, struct device_attribute *attr, char *buf)
98 struct bsr_dev *bsr_dev = dev_get_drvdata(dev);
99 return sprintf(buf, "%u\n", bsr_dev->bsr_stride);
103 bsr_len_show(struct device *dev, struct device_attribute *attr, char *buf)
105 struct bsr_dev *bsr_dev = dev_get_drvdata(dev);
106 return sprintf(buf, "%llu\n", bsr_dev->bsr_len);
109 static struct device_attribute bsr_dev_attrs[] = {
110 __ATTR(bsr_size, S_IRUGO, bsr_size_show, NULL),
111 __ATTR(bsr_stride, S_IRUGO, bsr_stride_show, NULL),
112 __ATTR(bsr_length, S_IRUGO, bsr_len_show, NULL),
116 static int bsr_mmap(struct file *filp, struct vm_area_struct *vma)
118 unsigned long size = vma->vm_end - vma->vm_start;
119 struct bsr_dev *dev = filp->private_data;
121 if (size > dev->bsr_len || (size & (PAGE_SIZE-1)))
124 vma->vm_flags |= (VM_IO | VM_DONTEXPAND);
125 vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
127 if (io_remap_pfn_range(vma, vma->vm_start, dev->bsr_addr >> PAGE_SHIFT,
128 size, vma->vm_page_prot))
134 static int bsr_open(struct inode * inode, struct file * filp)
136 struct cdev *cdev = inode->i_cdev;
137 struct bsr_dev *dev = container_of(cdev, struct bsr_dev, bsr_cdev);
139 filp->private_data = dev;
143 const static struct file_operations bsr_fops = {
144 .owner = THIS_MODULE,
149 static void bsr_cleanup_devs(void)
151 struct bsr_dev *cur, *n;
153 list_for_each_entry_safe(cur, n, &bsr_devs, bsr_list) {
154 if (cur->bsr_device) {
155 cdev_del(&cur->bsr_cdev);
156 device_del(cur->bsr_device);
158 list_del(&cur->bsr_list);
163 static int bsr_add_node(struct device_node *bn)
165 int bsr_stride_len, bsr_bytes_len, num_bsr_devs;
166 const u32 *bsr_stride;
167 const u32 *bsr_bytes;
171 bsr_stride = of_get_property(bn, "ibm,lock-stride", &bsr_stride_len);
172 bsr_bytes = of_get_property(bn, "ibm,#lock-bytes", &bsr_bytes_len);
174 if (!bsr_stride || !bsr_bytes ||
175 (bsr_stride_len != bsr_bytes_len)) {
176 printk(KERN_ERR "bsr of-node has missing/incorrect property\n");
180 num_bsr_devs = bsr_bytes_len / sizeof(u32);
182 for (i = 0 ; i < num_bsr_devs; i++) {
183 struct bsr_dev *cur = kzalloc(sizeof(struct bsr_dev),
189 printk(KERN_ERR "Unable to alloc bsr dev\n");
194 result = of_address_to_resource(bn, i, &res);
196 printk(KERN_ERR "bsr of-node has invalid reg property, skipping\n");
201 cur->bsr_minor = i + total_bsr_devs;
202 cur->bsr_addr = res.start;
203 cur->bsr_len = res.end - res.start + 1;
204 cur->bsr_bytes = bsr_bytes[i];
205 cur->bsr_stride = bsr_stride[i];
206 cur->bsr_dev = MKDEV(bsr_major, i + total_bsr_devs);
208 switch(cur->bsr_bytes) {
210 cur->bsr_type = BSR_8;
213 cur->bsr_type = BSR_16;
216 cur->bsr_type = BSR_64;
219 cur->bsr_type = BSR_128;
222 cur->bsr_type = BSR_UNKNOWN;
223 printk(KERN_INFO "unknown BSR size %d\n",cur->bsr_bytes);
226 cur->bsr_num = bsr_types[cur->bsr_type];
227 snprintf(cur->bsr_name, 32, "bsr%d_%d",
228 cur->bsr_bytes, cur->bsr_num);
230 cdev_init(&cur->bsr_cdev, &bsr_fops);
231 result = cdev_add(&cur->bsr_cdev, cur->bsr_dev, 1);
237 cur->bsr_device = device_create(bsr_class, NULL, cur->bsr_dev,
239 if (!cur->bsr_device) {
240 printk(KERN_ERR "device_create failed for %s\n",
242 cdev_del(&cur->bsr_cdev);
247 bsr_types[cur->bsr_type] = cur->bsr_num + 1;
248 list_add_tail(&cur->bsr_list, &bsr_devs);
251 total_bsr_devs += num_bsr_devs;
261 static int bsr_create_devs(struct device_node *bn)
266 ret = bsr_add_node(bn);
271 bn = of_find_compatible_node(bn, NULL, "ibm,bsr");
276 static int __init bsr_init(void)
278 struct device_node *np;
279 dev_t bsr_dev = MKDEV(bsr_major, 0);
283 np = of_find_compatible_node(NULL, NULL, "ibm,bsr");
287 bsr_class = class_create(THIS_MODULE, "bsr");
288 if (IS_ERR(bsr_class)) {
289 printk(KERN_ERR "class_create() failed for bsr_class\n");
292 bsr_class->dev_attrs = bsr_dev_attrs;
294 result = alloc_chrdev_region(&bsr_dev, 0, BSR_MAX_DEVS, "bsr");
295 bsr_major = MAJOR(bsr_dev);
297 printk(KERN_ERR "alloc_chrdev_region() failed for bsr\n");
301 if ((ret = bsr_create_devs(np)) < 0) {
309 unregister_chrdev_region(bsr_dev, BSR_MAX_DEVS);
312 class_destroy(bsr_class);
322 static void __exit bsr_exit(void)
328 class_destroy(bsr_class);
331 unregister_chrdev_region(MKDEV(bsr_major, 0), BSR_MAX_DEVS);
334 module_init(bsr_init);
335 module_exit(bsr_exit);
336 MODULE_LICENSE("GPL");
337 MODULE_AUTHOR("Sonny Rao <sonnyrao@us.ibm.com>");