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/kernel.h> 10 #include <linux/of.h> 11 #include <linux/of_address.h> 12 #include <linux/of_device.h> 13 #include <linux/of_platform.h> 14 #include <linux/fs.h> 15 #include <linux/module.h> 16 #include <linux/cdev.h> 17 #include <linux/list.h> 18 #include <linux/mm.h> 19 #include <linux/slab.h> 20 #include <asm/io.h> 21 22 /* 23 This driver exposes a special register which can be used for fast 24 synchronization across a large SMP machine. The hardware is exposed 25 as an array of bytes where each process will write to one of the bytes to 26 indicate it has finished the current stage and this update is broadcast to 27 all processors without having to bounce a cacheline between them. In 28 POWER5 and POWER6 there is one of these registers per SMP, but it is 29 presented in two forms; first, it is given as a whole and then as a number 30 of smaller registers which alias to parts of the single whole register. 31 This can potentially allow multiple groups of processes to each have their 32 own private synchronization device. 33 34 Note that this hardware *must* be written to using *only* single byte writes. 35 It may be read using 1, 2, 4, or 8 byte loads which must be aligned since 36 this region is treated as cache-inhibited processes should also use a 37 full sync before and after writing to the BSR to ensure all stores and 38 the BSR update have made it to all chips in the system 39 */ 40 41 /* This is arbitrary number, up to Power6 it's been 17 or fewer */ 42 #define BSR_MAX_DEVS (32) 43 44 struct bsr_dev { 45 u64 bsr_addr; /* Real address */ 46 u64 bsr_len; /* length of mem region we can map */ 47 unsigned bsr_bytes; /* size of the BSR reg itself */ 48 unsigned bsr_stride; /* interval at which BSR repeats in the page */ 49 unsigned bsr_type; /* maps to enum below */ 50 unsigned bsr_num; /* bsr id number for its type */ 51 int bsr_minor; 52 53 struct list_head bsr_list; 54 55 dev_t bsr_dev; 56 struct cdev bsr_cdev; 57 struct device *bsr_device; 58 char bsr_name[32]; 59 60 }; 61 62 static unsigned total_bsr_devs; 63 static LIST_HEAD(bsr_devs); 64 static int bsr_major; 65 66 enum { 67 BSR_8 = 0, 68 BSR_16 = 1, 69 BSR_64 = 2, 70 BSR_128 = 3, 71 BSR_4096 = 4, 72 BSR_UNKNOWN = 5, 73 BSR_MAX = 6, 74 }; 75 76 static unsigned bsr_types[BSR_MAX]; 77 78 static ssize_t 79 bsr_size_show(struct device *dev, struct device_attribute *attr, char *buf) 80 { 81 struct bsr_dev *bsr_dev = dev_get_drvdata(dev); 82 return sprintf(buf, "%u\n", bsr_dev->bsr_bytes); 83 } 84 static DEVICE_ATTR_RO(bsr_size); 85 86 static ssize_t 87 bsr_stride_show(struct device *dev, struct device_attribute *attr, char *buf) 88 { 89 struct bsr_dev *bsr_dev = dev_get_drvdata(dev); 90 return sprintf(buf, "%u\n", bsr_dev->bsr_stride); 91 } 92 static DEVICE_ATTR_RO(bsr_stride); 93 94 static ssize_t 95 bsr_length_show(struct device *dev, struct device_attribute *attr, char *buf) 96 { 97 struct bsr_dev *bsr_dev = dev_get_drvdata(dev); 98 return sprintf(buf, "%llu\n", bsr_dev->bsr_len); 99 } 100 static DEVICE_ATTR_RO(bsr_length); 101 102 static struct attribute *bsr_dev_attrs[] = { 103 &dev_attr_bsr_size.attr, 104 &dev_attr_bsr_stride.attr, 105 &dev_attr_bsr_length.attr, 106 NULL, 107 }; 108 ATTRIBUTE_GROUPS(bsr_dev); 109 110 static const struct class bsr_class = { 111 .name = "bsr", 112 .dev_groups = bsr_dev_groups, 113 }; 114 115 static int bsr_mmap(struct file *filp, struct vm_area_struct *vma) 116 { 117 unsigned long size = vma->vm_end - vma->vm_start; 118 struct bsr_dev *dev = filp->private_data; 119 int ret; 120 121 vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot); 122 123 /* check for the case of a small BSR device and map one 4k page for it*/ 124 if (dev->bsr_len < PAGE_SIZE && size == PAGE_SIZE) 125 ret = remap_4k_pfn(vma, vma->vm_start, dev->bsr_addr >> 12, 126 vma->vm_page_prot); 127 else if (size <= dev->bsr_len) 128 ret = io_remap_pfn_range(vma, vma->vm_start, 129 dev->bsr_addr >> PAGE_SHIFT, 130 size, vma->vm_page_prot); 131 else 132 return -EINVAL; 133 134 if (ret) 135 return -EAGAIN; 136 137 return 0; 138 } 139 140 static int bsr_open(struct inode *inode, struct file *filp) 141 { 142 struct cdev *cdev = inode->i_cdev; 143 struct bsr_dev *dev = container_of(cdev, struct bsr_dev, bsr_cdev); 144 145 filp->private_data = dev; 146 return 0; 147 } 148 149 static const struct file_operations bsr_fops = { 150 .owner = THIS_MODULE, 151 .mmap = bsr_mmap, 152 .open = bsr_open, 153 .llseek = noop_llseek, 154 }; 155 156 static void bsr_cleanup_devs(void) 157 { 158 struct bsr_dev *cur, *n; 159 160 list_for_each_entry_safe(cur, n, &bsr_devs, bsr_list) { 161 if (cur->bsr_device) { 162 cdev_del(&cur->bsr_cdev); 163 device_del(cur->bsr_device); 164 } 165 list_del(&cur->bsr_list); 166 kfree(cur); 167 } 168 } 169 170 static int bsr_add_node(struct device_node *bn) 171 { 172 int bsr_stride_len, bsr_bytes_len, num_bsr_devs; 173 const u32 *bsr_stride; 174 const u32 *bsr_bytes; 175 unsigned i; 176 int ret = -ENODEV; 177 178 bsr_stride = of_get_property(bn, "ibm,lock-stride", &bsr_stride_len); 179 bsr_bytes = of_get_property(bn, "ibm,#lock-bytes", &bsr_bytes_len); 180 181 if (!bsr_stride || !bsr_bytes || 182 (bsr_stride_len != bsr_bytes_len)) { 183 printk(KERN_ERR "bsr of-node has missing/incorrect property\n"); 184 return ret; 185 } 186 187 num_bsr_devs = bsr_bytes_len / sizeof(u32); 188 189 for (i = 0 ; i < num_bsr_devs; i++) { 190 struct bsr_dev *cur = kzalloc(sizeof(struct bsr_dev), 191 GFP_KERNEL); 192 struct resource res; 193 int result; 194 195 if (!cur) { 196 printk(KERN_ERR "Unable to alloc bsr dev\n"); 197 ret = -ENOMEM; 198 goto out_err; 199 } 200 201 result = of_address_to_resource(bn, i, &res); 202 if (result < 0) { 203 printk(KERN_ERR "bsr of-node has invalid reg property, skipping\n"); 204 kfree(cur); 205 continue; 206 } 207 208 cur->bsr_minor = i + total_bsr_devs; 209 cur->bsr_addr = res.start; 210 cur->bsr_len = resource_size(&res); 211 cur->bsr_bytes = bsr_bytes[i]; 212 cur->bsr_stride = bsr_stride[i]; 213 cur->bsr_dev = MKDEV(bsr_major, i + total_bsr_devs); 214 215 /* if we have a bsr_len of > 4k and less then PAGE_SIZE (64k pages) */ 216 /* we can only map 4k of it, so only advertise the 4k in sysfs */ 217 if (cur->bsr_len > 4096 && cur->bsr_len < PAGE_SIZE) 218 cur->bsr_len = 4096; 219 220 switch(cur->bsr_bytes) { 221 case 8: 222 cur->bsr_type = BSR_8; 223 break; 224 case 16: 225 cur->bsr_type = BSR_16; 226 break; 227 case 64: 228 cur->bsr_type = BSR_64; 229 break; 230 case 128: 231 cur->bsr_type = BSR_128; 232 break; 233 case 4096: 234 cur->bsr_type = BSR_4096; 235 break; 236 default: 237 cur->bsr_type = BSR_UNKNOWN; 238 } 239 240 cur->bsr_num = bsr_types[cur->bsr_type]; 241 snprintf(cur->bsr_name, 32, "bsr%d_%d", 242 cur->bsr_bytes, cur->bsr_num); 243 244 cdev_init(&cur->bsr_cdev, &bsr_fops); 245 result = cdev_add(&cur->bsr_cdev, cur->bsr_dev, 1); 246 if (result) { 247 kfree(cur); 248 goto out_err; 249 } 250 251 cur->bsr_device = device_create(&bsr_class, NULL, cur->bsr_dev, 252 cur, "%s", cur->bsr_name); 253 if (IS_ERR(cur->bsr_device)) { 254 printk(KERN_ERR "device_create failed for %s\n", 255 cur->bsr_name); 256 cdev_del(&cur->bsr_cdev); 257 kfree(cur); 258 goto out_err; 259 } 260 261 bsr_types[cur->bsr_type] = cur->bsr_num + 1; 262 list_add_tail(&cur->bsr_list, &bsr_devs); 263 } 264 265 total_bsr_devs += num_bsr_devs; 266 267 return 0; 268 269 out_err: 270 271 bsr_cleanup_devs(); 272 return ret; 273 } 274 275 static int bsr_create_devs(struct device_node *bn) 276 { 277 int ret; 278 279 while (bn) { 280 ret = bsr_add_node(bn); 281 if (ret) { 282 of_node_put(bn); 283 return ret; 284 } 285 bn = of_find_compatible_node(bn, NULL, "ibm,bsr"); 286 } 287 return 0; 288 } 289 290 static int __init bsr_init(void) 291 { 292 struct device_node *np; 293 dev_t bsr_dev; 294 int ret = -ENODEV; 295 296 np = of_find_compatible_node(NULL, NULL, "ibm,bsr"); 297 if (!np) 298 goto out_err; 299 300 ret = class_register(&bsr_class); 301 if (ret) 302 goto out_err_1; 303 304 ret = alloc_chrdev_region(&bsr_dev, 0, BSR_MAX_DEVS, "bsr"); 305 bsr_major = MAJOR(bsr_dev); 306 if (ret < 0) { 307 printk(KERN_ERR "alloc_chrdev_region() failed for bsr\n"); 308 goto out_err_2; 309 } 310 311 ret = bsr_create_devs(np); 312 if (ret < 0) { 313 np = NULL; 314 goto out_err_3; 315 } 316 317 return 0; 318 319 out_err_3: 320 unregister_chrdev_region(bsr_dev, BSR_MAX_DEVS); 321 322 out_err_2: 323 class_unregister(&bsr_class); 324 325 out_err_1: 326 of_node_put(np); 327 328 out_err: 329 330 return ret; 331 } 332 333 static void __exit bsr_exit(void) 334 { 335 336 bsr_cleanup_devs(); 337 338 class_unregister(&bsr_class); 339 340 if (bsr_major) 341 unregister_chrdev_region(MKDEV(bsr_major, 0), BSR_MAX_DEVS); 342 } 343 344 module_init(bsr_init); 345 module_exit(bsr_exit); 346 MODULE_LICENSE("GPL"); 347 MODULE_AUTHOR("Sonny Rao <sonnyrao@us.ibm.com>"); 348