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_obj(struct bsr_dev, GFP_KERNEL); 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 } 272 273 static 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 } 287 288 static 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 } 330 331 static 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 } 341 342 module_init(bsr_init); 343 module_exit(bsr_exit); 344 MODULE_DESCRIPTION("IBM POWER Barrier Synchronization Register Driver"); 345 MODULE_LICENSE("GPL"); 346 MODULE_AUTHOR("Sonny Rao <sonnyrao@us.ibm.com>"); 347