1 /* IBM POWER Barrier Synchronization Register Driver
2 *
3 * Copyright IBM Corporation 2008
4 *
5 * Author: Sonny Rao <sonnyrao@us.ibm.com>
6 *
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.
11 *
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.
16 *
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
20 */
21
22 #include <linux/kernel.h>
23 #include <linux/of.h>
24 #include <linux/of_address.h>
25 #include <linux/of_device.h>
26 #include <linux/of_platform.h>
27 #include <linux/fs.h>
28 #include <linux/module.h>
29 #include <linux/cdev.h>
30 #include <linux/list.h>
31 #include <linux/mm.h>
32 #include <linux/slab.h>
33 #include <asm/pgtable.h>
34 #include <asm/io.h>
35
36 /*
37 This driver exposes a special register which can be used for fast
38 synchronization across a large SMP machine. The hardware is exposed
39 as an array of bytes where each process will write to one of the bytes to
40 indicate it has finished the current stage and this update is broadcast to
41 all processors without having to bounce a cacheline between them. In
42 POWER5 and POWER6 there is one of these registers per SMP, but it is
43 presented in two forms; first, it is given as a whole and then as a number
44 of smaller registers which alias to parts of the single whole register.
45 This can potentially allow multiple groups of processes to each have their
46 own private synchronization device.
47
48 Note that this hardware *must* be written to using *only* single byte writes.
49 It may be read using 1, 2, 4, or 8 byte loads which must be aligned since
50 this region is treated as cache-inhibited processes should also use a
51 full sync before and after writing to the BSR to ensure all stores and
52 the BSR update have made it to all chips in the system
53 */
54
55 /* This is arbitrary number, up to Power6 it's been 17 or fewer */
56 #define BSR_MAX_DEVS (32)
57
58 struct bsr_dev {
59 u64 bsr_addr; /* Real address */
60 u64 bsr_len; /* length of mem region we can map */
61 unsigned bsr_bytes; /* size of the BSR reg itself */
62 unsigned bsr_stride; /* interval at which BSR repeats in the page */
63 unsigned bsr_type; /* maps to enum below */
64 unsigned bsr_num; /* bsr id number for its type */
65 int bsr_minor;
66
67 struct list_head bsr_list;
68
69 dev_t bsr_dev;
70 struct cdev bsr_cdev;
71 struct device *bsr_device;
72 char bsr_name[32];
73
74 };
75
76 static unsigned total_bsr_devs;
77 static struct list_head bsr_devs = LIST_HEAD_INIT(bsr_devs);
78 static struct class *bsr_class;
79 static int bsr_major;
80
81 enum {
82 BSR_8 = 0,
83 BSR_16 = 1,
84 BSR_64 = 2,
85 BSR_128 = 3,
86 BSR_4096 = 4,
87 BSR_UNKNOWN = 5,
88 BSR_MAX = 6,
89 };
90
91 static unsigned bsr_types[BSR_MAX];
92
93 static ssize_t
bsr_size_show(struct device * dev,struct device_attribute * attr,char * buf)94 bsr_size_show(struct device *dev, struct device_attribute *attr, char *buf)
95 {
96 struct bsr_dev *bsr_dev = dev_get_drvdata(dev);
97 return sprintf(buf, "%u\n", bsr_dev->bsr_bytes);
98 }
99 static DEVICE_ATTR_RO(bsr_size);
100
101 static ssize_t
bsr_stride_show(struct device * dev,struct device_attribute * attr,char * buf)102 bsr_stride_show(struct device *dev, struct device_attribute *attr, char *buf)
103 {
104 struct bsr_dev *bsr_dev = dev_get_drvdata(dev);
105 return sprintf(buf, "%u\n", bsr_dev->bsr_stride);
106 }
107 static DEVICE_ATTR_RO(bsr_stride);
108
109 static ssize_t
bsr_length_show(struct device * dev,struct device_attribute * attr,char * buf)110 bsr_length_show(struct device *dev, struct device_attribute *attr, char *buf)
111 {
112 struct bsr_dev *bsr_dev = dev_get_drvdata(dev);
113 return sprintf(buf, "%llu\n", bsr_dev->bsr_len);
114 }
115 static DEVICE_ATTR_RO(bsr_length);
116
117 static struct attribute *bsr_dev_attrs[] = {
118 &dev_attr_bsr_size.attr,
119 &dev_attr_bsr_stride.attr,
120 &dev_attr_bsr_length.attr,
121 NULL,
122 };
123 ATTRIBUTE_GROUPS(bsr_dev);
124
bsr_mmap(struct file * filp,struct vm_area_struct * vma)125 static int bsr_mmap(struct file *filp, struct vm_area_struct *vma)
126 {
127 unsigned long size = vma->vm_end - vma->vm_start;
128 struct bsr_dev *dev = filp->private_data;
129 int ret;
130
131 vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
132
133 /* check for the case of a small BSR device and map one 4k page for it*/
134 if (dev->bsr_len < PAGE_SIZE && size == PAGE_SIZE)
135 ret = remap_4k_pfn(vma, vma->vm_start, dev->bsr_addr >> 12,
136 vma->vm_page_prot);
137 else if (size <= dev->bsr_len)
138 ret = io_remap_pfn_range(vma, vma->vm_start,
139 dev->bsr_addr >> PAGE_SHIFT,
140 size, vma->vm_page_prot);
141 else
142 return -EINVAL;
143
144 if (ret)
145 return -EAGAIN;
146
147 return 0;
148 }
149
bsr_open(struct inode * inode,struct file * filp)150 static int bsr_open(struct inode * inode, struct file * filp)
151 {
152 struct cdev *cdev = inode->i_cdev;
153 struct bsr_dev *dev = container_of(cdev, struct bsr_dev, bsr_cdev);
154
155 filp->private_data = dev;
156 return 0;
157 }
158
159 static const struct file_operations bsr_fops = {
160 .owner = THIS_MODULE,
161 .mmap = bsr_mmap,
162 .open = bsr_open,
163 .llseek = noop_llseek,
164 };
165
bsr_cleanup_devs(void)166 static void bsr_cleanup_devs(void)
167 {
168 struct bsr_dev *cur, *n;
169
170 list_for_each_entry_safe(cur, n, &bsr_devs, bsr_list) {
171 if (cur->bsr_device) {
172 cdev_del(&cur->bsr_cdev);
173 device_del(cur->bsr_device);
174 }
175 list_del(&cur->bsr_list);
176 kfree(cur);
177 }
178 }
179
bsr_add_node(struct device_node * bn)180 static int bsr_add_node(struct device_node *bn)
181 {
182 int bsr_stride_len, bsr_bytes_len, num_bsr_devs;
183 const u32 *bsr_stride;
184 const u32 *bsr_bytes;
185 unsigned i;
186 int ret = -ENODEV;
187
188 bsr_stride = of_get_property(bn, "ibm,lock-stride", &bsr_stride_len);
189 bsr_bytes = of_get_property(bn, "ibm,#lock-bytes", &bsr_bytes_len);
190
191 if (!bsr_stride || !bsr_bytes ||
192 (bsr_stride_len != bsr_bytes_len)) {
193 printk(KERN_ERR "bsr of-node has missing/incorrect property\n");
194 return ret;
195 }
196
197 num_bsr_devs = bsr_bytes_len / sizeof(u32);
198
199 for (i = 0 ; i < num_bsr_devs; i++) {
200 struct bsr_dev *cur = kzalloc(sizeof(struct bsr_dev),
201 GFP_KERNEL);
202 struct resource res;
203 int result;
204
205 if (!cur) {
206 printk(KERN_ERR "Unable to alloc bsr dev\n");
207 ret = -ENOMEM;
208 goto out_err;
209 }
210
211 result = of_address_to_resource(bn, i, &res);
212 if (result < 0) {
213 printk(KERN_ERR "bsr of-node has invalid reg property, skipping\n");
214 kfree(cur);
215 continue;
216 }
217
218 cur->bsr_minor = i + total_bsr_devs;
219 cur->bsr_addr = res.start;
220 cur->bsr_len = resource_size(&res);
221 cur->bsr_bytes = bsr_bytes[i];
222 cur->bsr_stride = bsr_stride[i];
223 cur->bsr_dev = MKDEV(bsr_major, i + total_bsr_devs);
224
225 /* if we have a bsr_len of > 4k and less then PAGE_SIZE (64k pages) */
226 /* we can only map 4k of it, so only advertise the 4k in sysfs */
227 if (cur->bsr_len > 4096 && cur->bsr_len < PAGE_SIZE)
228 cur->bsr_len = 4096;
229
230 switch(cur->bsr_bytes) {
231 case 8:
232 cur->bsr_type = BSR_8;
233 break;
234 case 16:
235 cur->bsr_type = BSR_16;
236 break;
237 case 64:
238 cur->bsr_type = BSR_64;
239 break;
240 case 128:
241 cur->bsr_type = BSR_128;
242 break;
243 case 4096:
244 cur->bsr_type = BSR_4096;
245 break;
246 default:
247 cur->bsr_type = BSR_UNKNOWN;
248 }
249
250 cur->bsr_num = bsr_types[cur->bsr_type];
251 snprintf(cur->bsr_name, 32, "bsr%d_%d",
252 cur->bsr_bytes, cur->bsr_num);
253
254 cdev_init(&cur->bsr_cdev, &bsr_fops);
255 result = cdev_add(&cur->bsr_cdev, cur->bsr_dev, 1);
256 if (result) {
257 kfree(cur);
258 goto out_err;
259 }
260
261 cur->bsr_device = device_create(bsr_class, NULL, cur->bsr_dev,
262 cur, "%s", cur->bsr_name);
263 if (IS_ERR(cur->bsr_device)) {
264 printk(KERN_ERR "device_create failed for %s\n",
265 cur->bsr_name);
266 cdev_del(&cur->bsr_cdev);
267 kfree(cur);
268 goto out_err;
269 }
270
271 bsr_types[cur->bsr_type] = cur->bsr_num + 1;
272 list_add_tail(&cur->bsr_list, &bsr_devs);
273 }
274
275 total_bsr_devs += num_bsr_devs;
276
277 return 0;
278
279 out_err:
280
281 bsr_cleanup_devs();
282 return ret;
283 }
284
bsr_create_devs(struct device_node * bn)285 static int bsr_create_devs(struct device_node *bn)
286 {
287 int ret;
288
289 while (bn) {
290 ret = bsr_add_node(bn);
291 if (ret) {
292 of_node_put(bn);
293 return ret;
294 }
295 bn = of_find_compatible_node(bn, NULL, "ibm,bsr");
296 }
297 return 0;
298 }
299
bsr_init(void)300 static int __init bsr_init(void)
301 {
302 struct device_node *np;
303 dev_t bsr_dev;
304 int ret = -ENODEV;
305
306 np = of_find_compatible_node(NULL, NULL, "ibm,bsr");
307 if (!np)
308 goto out_err;
309
310 bsr_class = class_create(THIS_MODULE, "bsr");
311 if (IS_ERR(bsr_class)) {
312 printk(KERN_ERR "class_create() failed for bsr_class\n");
313 ret = PTR_ERR(bsr_class);
314 goto out_err_1;
315 }
316 bsr_class->dev_groups = bsr_dev_groups;
317
318 ret = alloc_chrdev_region(&bsr_dev, 0, BSR_MAX_DEVS, "bsr");
319 bsr_major = MAJOR(bsr_dev);
320 if (ret < 0) {
321 printk(KERN_ERR "alloc_chrdev_region() failed for bsr\n");
322 goto out_err_2;
323 }
324
325 if ((ret = bsr_create_devs(np)) < 0) {
326 np = NULL;
327 goto out_err_3;
328 }
329
330 return 0;
331
332 out_err_3:
333 unregister_chrdev_region(bsr_dev, BSR_MAX_DEVS);
334
335 out_err_2:
336 class_destroy(bsr_class);
337
338 out_err_1:
339 of_node_put(np);
340
341 out_err:
342
343 return ret;
344 }
345
bsr_exit(void)346 static void __exit bsr_exit(void)
347 {
348
349 bsr_cleanup_devs();
350
351 if (bsr_class)
352 class_destroy(bsr_class);
353
354 if (bsr_major)
355 unregister_chrdev_region(MKDEV(bsr_major, 0), BSR_MAX_DEVS);
356 }
357
358 module_init(bsr_init);
359 module_exit(bsr_exit);
360 MODULE_LICENSE("GPL");
361 MODULE_AUTHOR("Sonny Rao <sonnyrao@us.ibm.com>");
362