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 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 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 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 }; 113 114 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 } 138 139 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 }; 154 155 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 } 168 169 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 } 273 274 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 } 288 289 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 } 331 332 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_DESCRIPTION("IBM POWER Barrier Synchronization Register Driver"); 346 MODULE_LICENSE("GPL"); 347 MODULE_AUTHOR("Sonny Rao <sonnyrao@us.ibm.com>"); 348