projects/linux·blob master · refs

346 lines · 8.1 KiB

1// SPDX-License-Identifier: GPL-2.0-or-later
2/* IBM POWER Barrier Synchronization Register Driver
3 *
4 * Copyright IBM Corporation 2008
5 *
6 * Author: Sonny Rao <[email protected]>
7 */
8
9#include <linux/device.h>
10#include <linux/kernel.h>
11#include <linux/of.h>
12#include <linux/of_address.h>
13#include <linux/fs.h>
14#include <linux/module.h>
15#include <linux/cdev.h>
16#include <linux/list.h>
17#include <linux/mm.h>
18#include <linux/slab.h>
19#include <asm/io.h>
20
21/*
22 This driver exposes a special register which can be used for fast
23 synchronization across a large SMP machine. The hardware is exposed
24 as an array of bytes where each process will write to one of the bytes to
25 indicate it has finished the current stage and this update is broadcast to
26 all processors without having to bounce a cacheline between them. In
27 POWER5 and POWER6 there is one of these registers per SMP, but it is
28 presented in two forms; first, it is given as a whole and then as a number
29 of smaller registers which alias to parts of the single whole register.
30 This can potentially allow multiple groups of processes to each have their
31 own private synchronization device.
32
33 Note that this hardware *must* be written to using *only* single byte writes.
34 It may be read using 1, 2, 4, or 8 byte loads which must be aligned since
35 this region is treated as cache-inhibited processes should also use a
36 full sync before and after writing to the BSR to ensure all stores and
37 the BSR update have made it to all chips in the system
38*/
39
40/* This is arbitrary number, up to Power6 it's been 17 or fewer */
41#define BSR_MAX_DEVS (32)
42
43struct bsr_dev {
44 u64 bsr_addr; /* Real address */
45 u64 bsr_len; /* length of mem region we can map */
46 unsigned bsr_bytes; /* size of the BSR reg itself */
47 unsigned bsr_stride; /* interval at which BSR repeats in the page */
48 unsigned bsr_type; /* maps to enum below */
49 unsigned bsr_num; /* bsr id number for its type */
50 int bsr_minor;
51
52 struct list_head bsr_list;
53
54 dev_t bsr_dev;
55 struct cdev bsr_cdev;
56 struct device *bsr_device;
57 char bsr_name[32];
58
59};
60
61static unsigned total_bsr_devs;
62static LIST_HEAD(bsr_devs);
63static int bsr_major;
64
65enum {
66 BSR_8 = 0,
67 BSR_16 = 1,
68 BSR_64 = 2,
69 BSR_128 = 3,
70 BSR_4096 = 4,
71 BSR_UNKNOWN = 5,
72 BSR_MAX = 6,
73};
74
75static unsigned bsr_types[BSR_MAX];
76
77static ssize_t
78bsr_size_show(struct device *dev, struct device_attribute *attr, char *buf)
79{
80 struct bsr_dev *bsr_dev = dev_get_drvdata(dev);
81 return sprintf(buf, "%u\n", bsr_dev->bsr_bytes);
82}
83static DEVICE_ATTR_RO(bsr_size);
84
85static ssize_t
86bsr_stride_show(struct device *dev, struct device_attribute *attr, char *buf)
87{
88 struct bsr_dev *bsr_dev = dev_get_drvdata(dev);
89 return sprintf(buf, "%u\n", bsr_dev->bsr_stride);
90}
91static DEVICE_ATTR_RO(bsr_stride);
92
93static ssize_t
94bsr_length_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, "%llu\n", bsr_dev->bsr_len);
98}
99static DEVICE_ATTR_RO(bsr_length);
100
101static struct attribute *bsr_dev_attrs[] = {
102 &dev_attr_bsr_size.attr,
103 &dev_attr_bsr_stride.attr,
104 &dev_attr_bsr_length.attr,
105 NULL,
106};
107ATTRIBUTE_GROUPS(bsr_dev);
108
109static const struct class bsr_class = {
110 .name = "bsr",
111 .dev_groups = bsr_dev_groups,
112};
113
114static int bsr_mmap(struct file *filp, struct vm_area_struct *vma)
115{
116 unsigned long size = vma->vm_end - vma->vm_start;
117 struct bsr_dev *dev = filp->private_data;
118 int ret;
119
120 vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
121
122 /* check for the case of a small BSR device and map one 4k page for it*/
123 if (dev->bsr_len < PAGE_SIZE && size == PAGE_SIZE)
124 ret = remap_4k_pfn(vma, vma->vm_start, dev->bsr_addr >> 12,
125 vma->vm_page_prot);
126 else if (size <= dev->bsr_len)
127 ret = io_remap_pfn_range(vma, vma->vm_start,
128 dev->bsr_addr >> PAGE_SHIFT,
129 size, vma->vm_page_prot);
130 else
131 return -EINVAL;
132
133 if (ret)
134 return -EAGAIN;
135
136 return 0;
137}
138
139static int bsr_open(struct inode *inode, struct file *filp)
140{
141 struct cdev *cdev = inode->i_cdev;
142 struct bsr_dev *dev = container_of(cdev, struct bsr_dev, bsr_cdev);
143
144 filp->private_data = dev;
145 return 0;
146}
147
148static const struct file_operations bsr_fops = {
149 .owner = THIS_MODULE,
150 .mmap = bsr_mmap,
151 .open = bsr_open,
152 .llseek = noop_llseek,
153};
154
155static void bsr_cleanup_devs(void)
156{
157 struct bsr_dev *cur, *n;
158
159 list_for_each_entry_safe(cur, n, &bsr_devs, bsr_list) {
160 if (cur->bsr_device) {
161 cdev_del(&cur->bsr_cdev);
162 device_del(cur->bsr_device);
163 }
164 list_del(&cur->bsr_list);
165 kfree(cur);
166 }
167}
168
169static int bsr_add_node(struct device_node *bn)
170{
171 int bsr_stride_len, bsr_bytes_len, num_bsr_devs;
172 const u32 *bsr_stride;
173 const u32 *bsr_bytes;
174 unsigned i;
175 int ret = -ENODEV;
176
177 bsr_stride = of_get_property(bn, "ibm,lock-stride", &bsr_stride_len);
178 bsr_bytes = of_get_property(bn, "ibm,#lock-bytes", &bsr_bytes_len);
179
180 if (!bsr_stride || !bsr_bytes ||
181 (bsr_stride_len != bsr_bytes_len)) {
182 printk(KERN_ERR "bsr of-node has missing/incorrect property\n");
183 return ret;
184 }
185
186 num_bsr_devs = bsr_bytes_len / sizeof(u32);
187
188 for (i = 0 ; i < num_bsr_devs; i++) {
189 struct bsr_dev *cur = kzalloc_obj(struct bsr_dev);
190 struct resource res;
191 int result;
192
193 if (!cur) {
194 printk(KERN_ERR "Unable to alloc bsr dev\n");
195 ret = -ENOMEM;
196 goto out_err;
197 }
198
199 result = of_address_to_resource(bn, i, &res);
200 if (result < 0) {
201 printk(KERN_ERR "bsr of-node has invalid reg property, skipping\n");
202 kfree(cur);
203 continue;
204 }
205
206 cur->bsr_minor = i + total_bsr_devs;
207 cur->bsr_addr = res.start;
208 cur->bsr_len = resource_size(&res);
209 cur->bsr_bytes = bsr_bytes[i];
210 cur->bsr_stride = bsr_stride[i];
211 cur->bsr_dev = MKDEV(bsr_major, i + total_bsr_devs);
212
213 /* if we have a bsr_len of > 4k and less then PAGE_SIZE (64k pages) */
214 /* we can only map 4k of it, so only advertise the 4k in sysfs */
215 if (cur->bsr_len > 4096 && cur->bsr_len < PAGE_SIZE)
216 cur->bsr_len = 4096;
217
218 switch(cur->bsr_bytes) {
219 case 8:
220 cur->bsr_type = BSR_8;
221 break;
222 case 16:
223 cur->bsr_type = BSR_16;
224 break;
225 case 64:
226 cur->bsr_type = BSR_64;
227 break;
228 case 128:
229 cur->bsr_type = BSR_128;
230 break;
231 case 4096:
232 cur->bsr_type = BSR_4096;
233 break;
234 default:
235 cur->bsr_type = BSR_UNKNOWN;
236 }
237
238 cur->bsr_num = bsr_types[cur->bsr_type];
239 snprintf(cur->bsr_name, 32, "bsr%d_%d",
240 cur->bsr_bytes, cur->bsr_num);
241
242 cdev_init(&cur->bsr_cdev, &bsr_fops);
243 result = cdev_add(&cur->bsr_cdev, cur->bsr_dev, 1);
244 if (result) {
245 kfree(cur);
246 goto out_err;
247 }
248
249 cur->bsr_device = device_create(&bsr_class, NULL, cur->bsr_dev,
250 cur, "%s", cur->bsr_name);
251 if (IS_ERR(cur->bsr_device)) {
252 printk(KERN_ERR "device_create failed for %s\n",
253 cur->bsr_name);
254 cdev_del(&cur->bsr_cdev);
255 kfree(cur);
256 goto out_err;
257 }
258
259 bsr_types[cur->bsr_type] = cur->bsr_num + 1;
260 list_add_tail(&cur->bsr_list, &bsr_devs);
261 }
262
263 total_bsr_devs += num_bsr_devs;
264
265 return 0;
266
267 out_err:
268
269 bsr_cleanup_devs();
270 return ret;
271}
272
273static int bsr_create_devs(struct device_node *bn)
274{
275 int ret;
276
277 while (bn) {
278 ret = bsr_add_node(bn);
279 if (ret) {
280 of_node_put(bn);
281 return ret;
282 }
283 bn = of_find_compatible_node(bn, NULL, "ibm,bsr");
284 }
285 return 0;
286}
287
288static int __init bsr_init(void)
289{
290 struct device_node *np;
291 dev_t bsr_dev;
292 int ret = -ENODEV;
293
294 np = of_find_compatible_node(NULL, NULL, "ibm,bsr");
295 if (!np)
296 goto out_err;
297
298 ret = class_register(&bsr_class);
299 if (ret)
300 goto out_err_1;
301
302 ret = alloc_chrdev_region(&bsr_dev, 0, BSR_MAX_DEVS, "bsr");
303 bsr_major = MAJOR(bsr_dev);
304 if (ret < 0) {
305 printk(KERN_ERR "alloc_chrdev_region() failed for bsr\n");
306 goto out_err_2;
307 }
308
309 ret = bsr_create_devs(np);
310 if (ret < 0) {
311 np = NULL;
312 goto out_err_3;
313 }
314
315 return 0;
316
317 out_err_3:
318 unregister_chrdev_region(bsr_dev, BSR_MAX_DEVS);
319
320 out_err_2:
321 class_unregister(&bsr_class);
322
323 out_err_1:
324 of_node_put(np);
325
326 out_err:
327
328 return ret;
329}
330
331static void __exit bsr_exit(void)
332{
333
334 bsr_cleanup_devs();
335
336 class_unregister(&bsr_class);
337
338 if (bsr_major)
339 unregister_chrdev_region(MKDEV(bsr_major, 0), BSR_MAX_DEVS);
340}
341
342module_init(bsr_init);
343module_exit(bsr_exit);
344MODULE_DESCRIPTION("IBM POWER Barrier Synchronization Register Driver");
345MODULE_LICENSE("GPL");
346MODULE_AUTHOR("Sonny Rao <[email protected]>");