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 struct list_head bsr_devs = LIST_HEAD_INIT(bsr_devs); 64 static struct class *bsr_class; 65 static int bsr_major; 66 67 enum { 68 BSR_8 = 0, 69 BSR_16 = 1, 70 BSR_64 = 2, 71 BSR_128 = 3, 72 BSR_4096 = 4, 73 BSR_UNKNOWN = 5, 74 BSR_MAX = 6, 75 }; 76 77 static unsigned bsr_types[BSR_MAX]; 78 79 static ssize_t 80 bsr_size_show(struct device *dev, struct device_attribute *attr, char *buf) 81 { 82 struct bsr_dev *bsr_dev = dev_get_drvdata(dev); 83 return sprintf(buf, "%u\n", bsr_dev->bsr_bytes); 84 } 85 static DEVICE_ATTR_RO(bsr_size); 86 87 static ssize_t 88 bsr_stride_show(struct device *dev, struct device_attribute *attr, char *buf) 89 { 90 struct bsr_dev *bsr_dev = dev_get_drvdata(dev); 91 return sprintf(buf, "%u\n", bsr_dev->bsr_stride); 92 } 93 static DEVICE_ATTR_RO(bsr_stride); 94 95 static ssize_t 96 bsr_length_show(struct device *dev, struct device_attribute *attr, char *buf) 97 { 98 struct bsr_dev *bsr_dev = dev_get_drvdata(dev); 99 return sprintf(buf, "%llu\n", bsr_dev->bsr_len); 100 } 101 static DEVICE_ATTR_RO(bsr_length); 102 103 static struct attribute *bsr_dev_attrs[] = { 104 &dev_attr_bsr_size.attr, 105 &dev_attr_bsr_stride.attr, 106 &dev_attr_bsr_length.attr, 107 NULL, 108 }; 109 ATTRIBUTE_GROUPS(bsr_dev); 110 111 static int bsr_mmap(struct file *filp, struct vm_area_struct *vma) 112 { 113 unsigned long size = vma->vm_end - vma->vm_start; 114 struct bsr_dev *dev = filp->private_data; 115 int ret; 116 117 vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot); 118 119 /* check for the case of a small BSR device and map one 4k page for it*/ 120 if (dev->bsr_len < PAGE_SIZE && size == PAGE_SIZE) 121 ret = remap_4k_pfn(vma, vma->vm_start, dev->bsr_addr >> 12, 122 vma->vm_page_prot); 123 else if (size <= dev->bsr_len) 124 ret = io_remap_pfn_range(vma, vma->vm_start, 125 dev->bsr_addr >> PAGE_SHIFT, 126 size, vma->vm_page_prot); 127 else 128 return -EINVAL; 129 130 if (ret) 131 return -EAGAIN; 132 133 return 0; 134 } 135 136 static int bsr_open(struct inode *inode, struct file *filp) 137 { 138 struct cdev *cdev = inode->i_cdev; 139 struct bsr_dev *dev = container_of(cdev, struct bsr_dev, bsr_cdev); 140 141 filp->private_data = dev; 142 return 0; 143 } 144 145 static const struct file_operations bsr_fops = { 146 .owner = THIS_MODULE, 147 .mmap = bsr_mmap, 148 .open = bsr_open, 149 .llseek = noop_llseek, 150 }; 151 152 static void bsr_cleanup_devs(void) 153 { 154 struct bsr_dev *cur, *n; 155 156 list_for_each_entry_safe(cur, n, &bsr_devs, bsr_list) { 157 if (cur->bsr_device) { 158 cdev_del(&cur->bsr_cdev); 159 device_del(cur->bsr_device); 160 } 161 list_del(&cur->bsr_list); 162 kfree(cur); 163 } 164 } 165 166 static int bsr_add_node(struct device_node *bn) 167 { 168 int bsr_stride_len, bsr_bytes_len, num_bsr_devs; 169 const u32 *bsr_stride; 170 const u32 *bsr_bytes; 171 unsigned i; 172 int ret = -ENODEV; 173 174 bsr_stride = of_get_property(bn, "ibm,lock-stride", &bsr_stride_len); 175 bsr_bytes = of_get_property(bn, "ibm,#lock-bytes", &bsr_bytes_len); 176 177 if (!bsr_stride || !bsr_bytes || 178 (bsr_stride_len != bsr_bytes_len)) { 179 printk(KERN_ERR "bsr of-node has missing/incorrect property\n"); 180 return ret; 181 } 182 183 num_bsr_devs = bsr_bytes_len / sizeof(u32); 184 185 for (i = 0 ; i < num_bsr_devs; i++) { 186 struct bsr_dev *cur = kzalloc(sizeof(struct bsr_dev), 187 GFP_KERNEL); 188 struct resource res; 189 int result; 190 191 if (!cur) { 192 printk(KERN_ERR "Unable to alloc bsr dev\n"); 193 ret = -ENOMEM; 194 goto out_err; 195 } 196 197 result = of_address_to_resource(bn, i, &res); 198 if (result < 0) { 199 printk(KERN_ERR "bsr of-node has invalid reg property, skipping\n"); 200 kfree(cur); 201 continue; 202 } 203 204 cur->bsr_minor = i + total_bsr_devs; 205 cur->bsr_addr = res.start; 206 cur->bsr_len = resource_size(&res); 207 cur->bsr_bytes = bsr_bytes[i]; 208 cur->bsr_stride = bsr_stride[i]; 209 cur->bsr_dev = MKDEV(bsr_major, i + total_bsr_devs); 210 211 /* if we have a bsr_len of > 4k and less then PAGE_SIZE (64k pages) */ 212 /* we can only map 4k of it, so only advertise the 4k in sysfs */ 213 if (cur->bsr_len > 4096 && cur->bsr_len < PAGE_SIZE) 214 cur->bsr_len = 4096; 215 216 switch(cur->bsr_bytes) { 217 case 8: 218 cur->bsr_type = BSR_8; 219 break; 220 case 16: 221 cur->bsr_type = BSR_16; 222 break; 223 case 64: 224 cur->bsr_type = BSR_64; 225 break; 226 case 128: 227 cur->bsr_type = BSR_128; 228 break; 229 case 4096: 230 cur->bsr_type = BSR_4096; 231 break; 232 default: 233 cur->bsr_type = BSR_UNKNOWN; 234 } 235 236 cur->bsr_num = bsr_types[cur->bsr_type]; 237 snprintf(cur->bsr_name, 32, "bsr%d_%d", 238 cur->bsr_bytes, cur->bsr_num); 239 240 cdev_init(&cur->bsr_cdev, &bsr_fops); 241 result = cdev_add(&cur->bsr_cdev, cur->bsr_dev, 1); 242 if (result) { 243 kfree(cur); 244 goto out_err; 245 } 246 247 cur->bsr_device = device_create(bsr_class, NULL, cur->bsr_dev, 248 cur, "%s", cur->bsr_name); 249 if (IS_ERR(cur->bsr_device)) { 250 printk(KERN_ERR "device_create failed for %s\n", 251 cur->bsr_name); 252 cdev_del(&cur->bsr_cdev); 253 kfree(cur); 254 goto out_err; 255 } 256 257 bsr_types[cur->bsr_type] = cur->bsr_num + 1; 258 list_add_tail(&cur->bsr_list, &bsr_devs); 259 } 260 261 total_bsr_devs += num_bsr_devs; 262 263 return 0; 264 265 out_err: 266 267 bsr_cleanup_devs(); 268 return ret; 269 } 270 271 static int bsr_create_devs(struct device_node *bn) 272 { 273 int ret; 274 275 while (bn) { 276 ret = bsr_add_node(bn); 277 if (ret) { 278 of_node_put(bn); 279 return ret; 280 } 281 bn = of_find_compatible_node(bn, NULL, "ibm,bsr"); 282 } 283 return 0; 284 } 285 286 static int __init bsr_init(void) 287 { 288 struct device_node *np; 289 dev_t bsr_dev; 290 int ret = -ENODEV; 291 292 np = of_find_compatible_node(NULL, NULL, "ibm,bsr"); 293 if (!np) 294 goto out_err; 295 296 bsr_class = class_create(THIS_MODULE, "bsr"); 297 if (IS_ERR(bsr_class)) { 298 printk(KERN_ERR "class_create() failed for bsr_class\n"); 299 ret = PTR_ERR(bsr_class); 300 goto out_err_1; 301 } 302 bsr_class->dev_groups = bsr_dev_groups; 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_destroy(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 if (bsr_class) 339 class_destroy(bsr_class); 340 341 if (bsr_major) 342 unregister_chrdev_region(MKDEV(bsr_major, 0), BSR_MAX_DEVS); 343 } 344 345 module_init(bsr_init); 346 module_exit(bsr_exit); 347 MODULE_LICENSE("GPL"); 348 MODULE_AUTHOR("Sonny Rao <sonnyrao@us.ibm.com>"); 349