xref: /openbmc/linux/drivers/char/bsr.c (revision 89f6fc9c)
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 <sonnyrao@us.ibm.com>
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 
43 struct 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 
61 static unsigned total_bsr_devs;
62 static LIST_HEAD(bsr_devs);
63 static int bsr_major;
64 
65 enum {
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 
75 static unsigned bsr_types[BSR_MAX];
76 
77 static ssize_t
bsr_size_show(struct device * dev,struct device_attribute * attr,char * buf)78 bsr_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 }
83 static DEVICE_ATTR_RO(bsr_size);
84 
85 static ssize_t
bsr_stride_show(struct device * dev,struct device_attribute * attr,char * buf)86 bsr_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 }
91 static DEVICE_ATTR_RO(bsr_stride);
92 
93 static ssize_t
bsr_length_show(struct device * dev,struct device_attribute * attr,char * buf)94 bsr_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 }
99 static DEVICE_ATTR_RO(bsr_length);
100 
101 static 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 };
107 ATTRIBUTE_GROUPS(bsr_dev);
108 
109 static const struct class bsr_class = {
110 	.name		= "bsr",
111 	.dev_groups	= bsr_dev_groups,
112 };
113 
bsr_mmap(struct file * filp,struct vm_area_struct * vma)114 static 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 
bsr_open(struct inode * inode,struct file * filp)139 static 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 
148 static const struct file_operations bsr_fops = {
149 	.owner = THIS_MODULE,
150 	.mmap  = bsr_mmap,
151 	.open  = bsr_open,
152 	.llseek = noop_llseek,
153 };
154 
bsr_cleanup_devs(void)155 static 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 
bsr_add_node(struct device_node * bn)169 static 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(sizeof(struct bsr_dev),
190 					      GFP_KERNEL);
191 		struct resource res;
192 		int result;
193 
194 		if (!cur) {
195 			printk(KERN_ERR "Unable to alloc bsr dev\n");
196 			ret = -ENOMEM;
197 			goto out_err;
198 		}
199 
200 		result = of_address_to_resource(bn, i, &res);
201 		if (result < 0) {
202 			printk(KERN_ERR "bsr of-node has invalid reg property, skipping\n");
203 			kfree(cur);
204 			continue;
205 		}
206 
207 		cur->bsr_minor  = i + total_bsr_devs;
208 		cur->bsr_addr   = res.start;
209 		cur->bsr_len    = resource_size(&res);
210 		cur->bsr_bytes  = bsr_bytes[i];
211 		cur->bsr_stride = bsr_stride[i];
212 		cur->bsr_dev    = MKDEV(bsr_major, i + total_bsr_devs);
213 
214 		/* if we have a bsr_len of > 4k and less then PAGE_SIZE (64k pages) */
215 		/* we can only map 4k of it, so only advertise the 4k in sysfs */
216 		if (cur->bsr_len > 4096 && cur->bsr_len < PAGE_SIZE)
217 			cur->bsr_len = 4096;
218 
219 		switch(cur->bsr_bytes) {
220 		case 8:
221 			cur->bsr_type = BSR_8;
222 			break;
223 		case 16:
224 			cur->bsr_type = BSR_16;
225 			break;
226 		case 64:
227 			cur->bsr_type = BSR_64;
228 			break;
229 		case 128:
230 			cur->bsr_type = BSR_128;
231 			break;
232 		case 4096:
233 			cur->bsr_type = BSR_4096;
234 			break;
235 		default:
236 			cur->bsr_type = BSR_UNKNOWN;
237 		}
238 
239 		cur->bsr_num = bsr_types[cur->bsr_type];
240 		snprintf(cur->bsr_name, 32, "bsr%d_%d",
241 			 cur->bsr_bytes, cur->bsr_num);
242 
243 		cdev_init(&cur->bsr_cdev, &bsr_fops);
244 		result = cdev_add(&cur->bsr_cdev, cur->bsr_dev, 1);
245 		if (result) {
246 			kfree(cur);
247 			goto out_err;
248 		}
249 
250 		cur->bsr_device = device_create(&bsr_class, NULL, cur->bsr_dev,
251 						cur, "%s", cur->bsr_name);
252 		if (IS_ERR(cur->bsr_device)) {
253 			printk(KERN_ERR "device_create failed for %s\n",
254 			       cur->bsr_name);
255 			cdev_del(&cur->bsr_cdev);
256 			kfree(cur);
257 			goto out_err;
258 		}
259 
260 		bsr_types[cur->bsr_type] = cur->bsr_num + 1;
261 		list_add_tail(&cur->bsr_list, &bsr_devs);
262 	}
263 
264 	total_bsr_devs += num_bsr_devs;
265 
266 	return 0;
267 
268  out_err:
269 
270 	bsr_cleanup_devs();
271 	return ret;
272 }
273 
bsr_create_devs(struct device_node * bn)274 static int bsr_create_devs(struct device_node *bn)
275 {
276 	int ret;
277 
278 	while (bn) {
279 		ret = bsr_add_node(bn);
280 		if (ret) {
281 			of_node_put(bn);
282 			return ret;
283 		}
284 		bn = of_find_compatible_node(bn, NULL, "ibm,bsr");
285 	}
286 	return 0;
287 }
288 
bsr_init(void)289 static int __init bsr_init(void)
290 {
291 	struct device_node *np;
292 	dev_t bsr_dev;
293 	int ret = -ENODEV;
294 
295 	np = of_find_compatible_node(NULL, NULL, "ibm,bsr");
296 	if (!np)
297 		goto out_err;
298 
299 	ret = class_register(&bsr_class);
300 	if (ret)
301 		goto out_err_1;
302 
303 	ret = alloc_chrdev_region(&bsr_dev, 0, BSR_MAX_DEVS, "bsr");
304 	bsr_major = MAJOR(bsr_dev);
305 	if (ret < 0) {
306 		printk(KERN_ERR "alloc_chrdev_region() failed for bsr\n");
307 		goto out_err_2;
308 	}
309 
310 	ret = bsr_create_devs(np);
311 	if (ret < 0) {
312 		np = NULL;
313 		goto out_err_3;
314 	}
315 
316 	return 0;
317 
318  out_err_3:
319 	unregister_chrdev_region(bsr_dev, BSR_MAX_DEVS);
320 
321  out_err_2:
322 	class_unregister(&bsr_class);
323 
324  out_err_1:
325 	of_node_put(np);
326 
327  out_err:
328 
329 	return ret;
330 }
331 
bsr_exit(void)332 static void __exit  bsr_exit(void)
333 {
334 
335 	bsr_cleanup_devs();
336 
337 	class_unregister(&bsr_class);
338 
339 	if (bsr_major)
340 		unregister_chrdev_region(MKDEV(bsr_major, 0), BSR_MAX_DEVS);
341 }
342 
343 module_init(bsr_init);
344 module_exit(bsr_exit);
345 MODULE_LICENSE("GPL");
346 MODULE_AUTHOR("Sonny Rao <sonnyrao@us.ibm.com>");
347