| 1 | /* IBM POWER Barrier Synchronization Register Driver |
| 2 | * |
| 3 | * Copyright IBM Corporation 2008 |
| 4 | * |
| 5 | * Author: Sonny Rao <sonnyrao@us.ibm.com> |
| 6 | * |
| 7 | * This program is free software; you can redistribute it and/or modify |
| 8 | * it under the terms of the GNU General Public License as published by |
| 9 | * the Free Software Foundation; either version 2 of the License, or |
| 10 | * (at your option) any later version. |
| 11 | * |
| 12 | * This program is distributed in the hope that it will be useful, |
| 13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 15 | * GNU General Public License for more details. |
| 16 | * |
| 17 | * You should have received a copy of the GNU General Public License |
| 18 | * along with this program; if not, write to the Free Software |
| 19 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
| 20 | */ |
| 21 | |
| 22 | #include <linux/kernel.h> |
| 23 | #include <linux/of.h> |
| 24 | #include <linux/of_device.h> |
| 25 | #include <linux/of_platform.h> |
| 26 | #include <linux/module.h> |
| 27 | #include <linux/cdev.h> |
| 28 | #include <linux/list.h> |
| 29 | #include <linux/mm.h> |
| 30 | #include <asm/pgtable.h> |
| 31 | #include <asm/io.h> |
| 32 | |
| 33 | /* |
| 34 | This driver exposes a special register which can be used for fast |
| 35 | synchronization across a large SMP machine. The hardware is exposed |
| 36 | as an array of bytes where each process will write to one of the bytes to |
| 37 | indicate it has finished the current stage and this update is broadcast to |
| 38 | all processors without having to bounce a cacheline between them. In |
| 39 | POWER5 and POWER6 there is one of these registers per SMP, but it is |
| 40 | presented in two forms; first, it is given as a whole and then as a number |
| 41 | of smaller registers which alias to parts of the single whole register. |
| 42 | This can potentially allow multiple groups of processes to each have their |
| 43 | own private synchronization device. |
| 44 | |
| 45 | Note that this hardware *must* be written to using *only* single byte writes. |
| 46 | It may be read using 1, 2, 4, or 8 byte loads which must be aligned since |
| 47 | this region is treated as cache-inhibited processes should also use a |
| 48 | full sync before and after writing to the BSR to ensure all stores and |
| 49 | the BSR update have made it to all chips in the system |
| 50 | */ |
| 51 | |
| 52 | /* This is arbitrary number, up to Power6 it's been 17 or fewer */ |
| 53 | #define BSR_MAX_DEVS (32) |
| 54 | |
| 55 | struct bsr_dev { |
| 56 | u64 bsr_addr; /* Real address */ |
| 57 | u64 bsr_len; /* length of mem region we can map */ |
| 58 | unsigned bsr_bytes; /* size of the BSR reg itself */ |
| 59 | unsigned bsr_stride; /* interval at which BSR repeats in the page */ |
| 60 | unsigned bsr_type; /* maps to enum below */ |
| 61 | unsigned bsr_num; /* bsr id number for its type */ |
| 62 | int bsr_minor; |
| 63 | |
| 64 | struct list_head bsr_list; |
| 65 | |
| 66 | dev_t bsr_dev; |
| 67 | struct cdev bsr_cdev; |
| 68 | struct device *bsr_device; |
| 69 | char bsr_name[32]; |
| 70 | |
| 71 | }; |
| 72 | |
| 73 | static unsigned total_bsr_devs; |
| 74 | static struct list_head bsr_devs = LIST_HEAD_INIT(bsr_devs); |
| 75 | static struct class *bsr_class; |
| 76 | static int bsr_major; |
| 77 | |
| 78 | enum { |
| 79 | BSR_8 = 0, |
| 80 | BSR_16 = 1, |
| 81 | BSR_64 = 2, |
| 82 | BSR_128 = 3, |
| 83 | BSR_4096 = 4, |
| 84 | BSR_UNKNOWN = 5, |
| 85 | BSR_MAX = 6, |
| 86 | }; |
| 87 | |
| 88 | static unsigned bsr_types[BSR_MAX]; |
| 89 | |
| 90 | static ssize_t |
| 91 | bsr_size_show(struct device *dev, struct device_attribute *attr, char *buf) |
| 92 | { |
| 93 | struct bsr_dev *bsr_dev = dev_get_drvdata(dev); |
| 94 | return sprintf(buf, "%u\n", bsr_dev->bsr_bytes); |
| 95 | } |
| 96 | |
| 97 | static ssize_t |
| 98 | bsr_stride_show(struct device *dev, struct device_attribute *attr, char *buf) |
| 99 | { |
| 100 | struct bsr_dev *bsr_dev = dev_get_drvdata(dev); |
| 101 | return sprintf(buf, "%u\n", bsr_dev->bsr_stride); |
| 102 | } |
| 103 | |
| 104 | static ssize_t |
| 105 | bsr_len_show(struct device *dev, struct device_attribute *attr, char *buf) |
| 106 | { |
| 107 | struct bsr_dev *bsr_dev = dev_get_drvdata(dev); |
| 108 | return sprintf(buf, "%llu\n", bsr_dev->bsr_len); |
| 109 | } |
| 110 | |
| 111 | static struct device_attribute bsr_dev_attrs[] = { |
| 112 | __ATTR(bsr_size, S_IRUGO, bsr_size_show, NULL), |
| 113 | __ATTR(bsr_stride, S_IRUGO, bsr_stride_show, NULL), |
| 114 | __ATTR(bsr_length, S_IRUGO, bsr_len_show, NULL), |
| 115 | __ATTR_NULL |
| 116 | }; |
| 117 | |
| 118 | static int bsr_mmap(struct file *filp, struct vm_area_struct *vma) |
| 119 | { |
| 120 | unsigned long size = vma->vm_end - vma->vm_start; |
| 121 | struct bsr_dev *dev = filp->private_data; |
| 122 | int ret; |
| 123 | |
| 124 | vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot); |
| 125 | |
| 126 | /* check for the case of a small BSR device and map one 4k page for it*/ |
| 127 | if (dev->bsr_len < PAGE_SIZE && size == PAGE_SIZE) |
| 128 | ret = remap_4k_pfn(vma, vma->vm_start, dev->bsr_addr >> 12, |
| 129 | vma->vm_page_prot); |
| 130 | else if (size <= dev->bsr_len) |
| 131 | ret = io_remap_pfn_range(vma, vma->vm_start, |
| 132 | dev->bsr_addr >> PAGE_SHIFT, |
| 133 | size, vma->vm_page_prot); |
| 134 | else |
| 135 | return -EINVAL; |
| 136 | |
| 137 | if (ret) |
| 138 | return -EAGAIN; |
| 139 | |
| 140 | return 0; |
| 141 | } |
| 142 | |
| 143 | static int bsr_open(struct inode * inode, struct file * filp) |
| 144 | { |
| 145 | struct cdev *cdev = inode->i_cdev; |
| 146 | struct bsr_dev *dev = container_of(cdev, struct bsr_dev, bsr_cdev); |
| 147 | |
| 148 | filp->private_data = dev; |
| 149 | return 0; |
| 150 | } |
| 151 | |
| 152 | static const struct file_operations bsr_fops = { |
| 153 | .owner = THIS_MODULE, |
| 154 | .mmap = bsr_mmap, |
| 155 | .open = bsr_open, |
| 156 | }; |
| 157 | |
| 158 | static void bsr_cleanup_devs(void) |
| 159 | { |
| 160 | struct bsr_dev *cur, *n; |
| 161 | |
| 162 | list_for_each_entry_safe(cur, n, &bsr_devs, bsr_list) { |
| 163 | if (cur->bsr_device) { |
| 164 | cdev_del(&cur->bsr_cdev); |
| 165 | device_del(cur->bsr_device); |
| 166 | } |
| 167 | list_del(&cur->bsr_list); |
| 168 | kfree(cur); |
| 169 | } |
| 170 | } |
| 171 | |
| 172 | static int bsr_add_node(struct device_node *bn) |
| 173 | { |
| 174 | int bsr_stride_len, bsr_bytes_len, num_bsr_devs; |
| 175 | const u32 *bsr_stride; |
| 176 | const u32 *bsr_bytes; |
| 177 | unsigned i; |
| 178 | int ret = -ENODEV; |
| 179 | |
| 180 | bsr_stride = of_get_property(bn, "ibm,lock-stride", &bsr_stride_len); |
| 181 | bsr_bytes = of_get_property(bn, "ibm,#lock-bytes", &bsr_bytes_len); |
| 182 | |
| 183 | if (!bsr_stride || !bsr_bytes || |
| 184 | (bsr_stride_len != bsr_bytes_len)) { |
| 185 | printk(KERN_ERR "bsr of-node has missing/incorrect property\n"); |
| 186 | return ret; |
| 187 | } |
| 188 | |
| 189 | num_bsr_devs = bsr_bytes_len / sizeof(u32); |
| 190 | |
| 191 | for (i = 0 ; i < num_bsr_devs; i++) { |
| 192 | struct bsr_dev *cur = kzalloc(sizeof(struct bsr_dev), |
| 193 | GFP_KERNEL); |
| 194 | struct resource res; |
| 195 | int result; |
| 196 | |
| 197 | if (!cur) { |
| 198 | printk(KERN_ERR "Unable to alloc bsr dev\n"); |
| 199 | ret = -ENOMEM; |
| 200 | goto out_err; |
| 201 | } |
| 202 | |
| 203 | result = of_address_to_resource(bn, i, &res); |
| 204 | if (result < 0) { |
| 205 | printk(KERN_ERR "bsr of-node has invalid reg property, skipping\n"); |
| 206 | kfree(cur); |
| 207 | continue; |
| 208 | } |
| 209 | |
| 210 | cur->bsr_minor = i + total_bsr_devs; |
| 211 | cur->bsr_addr = res.start; |
| 212 | cur->bsr_len = res.end - res.start + 1; |
| 213 | cur->bsr_bytes = bsr_bytes[i]; |
| 214 | cur->bsr_stride = bsr_stride[i]; |
| 215 | cur->bsr_dev = MKDEV(bsr_major, i + total_bsr_devs); |
| 216 | |
| 217 | /* if we have a bsr_len of > 4k and less then PAGE_SIZE (64k pages) */ |
| 218 | /* we can only map 4k of it, so only advertise the 4k in sysfs */ |
| 219 | if (cur->bsr_len > 4096 && cur->bsr_len < PAGE_SIZE) |
| 220 | cur->bsr_len = 4096; |
| 221 | |
| 222 | switch(cur->bsr_bytes) { |
| 223 | case 8: |
| 224 | cur->bsr_type = BSR_8; |
| 225 | break; |
| 226 | case 16: |
| 227 | cur->bsr_type = BSR_16; |
| 228 | break; |
| 229 | case 64: |
| 230 | cur->bsr_type = BSR_64; |
| 231 | break; |
| 232 | case 128: |
| 233 | cur->bsr_type = BSR_128; |
| 234 | break; |
| 235 | case 4096: |
| 236 | cur->bsr_type = BSR_4096; |
| 237 | break; |
| 238 | default: |
| 239 | cur->bsr_type = BSR_UNKNOWN; |
| 240 | } |
| 241 | |
| 242 | cur->bsr_num = bsr_types[cur->bsr_type]; |
| 243 | snprintf(cur->bsr_name, 32, "bsr%d_%d", |
| 244 | cur->bsr_bytes, cur->bsr_num); |
| 245 | |
| 246 | cdev_init(&cur->bsr_cdev, &bsr_fops); |
| 247 | result = cdev_add(&cur->bsr_cdev, cur->bsr_dev, 1); |
| 248 | if (result) { |
| 249 | kfree(cur); |
| 250 | goto out_err; |
| 251 | } |
| 252 | |
| 253 | cur->bsr_device = device_create(bsr_class, NULL, cur->bsr_dev, |
| 254 | cur, cur->bsr_name); |
| 255 | if (!cur->bsr_device) { |
| 256 | printk(KERN_ERR "device_create failed for %s\n", |
| 257 | cur->bsr_name); |
| 258 | cdev_del(&cur->bsr_cdev); |
| 259 | kfree(cur); |
| 260 | goto out_err; |
| 261 | } |
| 262 | |
| 263 | bsr_types[cur->bsr_type] = cur->bsr_num + 1; |
| 264 | list_add_tail(&cur->bsr_list, &bsr_devs); |
| 265 | } |
| 266 | |
| 267 | total_bsr_devs += num_bsr_devs; |
| 268 | |
| 269 | return 0; |
| 270 | |
| 271 | out_err: |
| 272 | |
| 273 | bsr_cleanup_devs(); |
| 274 | return ret; |
| 275 | } |
| 276 | |
| 277 | static int bsr_create_devs(struct device_node *bn) |
| 278 | { |
| 279 | int ret; |
| 280 | |
| 281 | while (bn) { |
| 282 | ret = bsr_add_node(bn); |
| 283 | if (ret) { |
| 284 | of_node_put(bn); |
| 285 | return ret; |
| 286 | } |
| 287 | bn = of_find_compatible_node(bn, NULL, "ibm,bsr"); |
| 288 | } |
| 289 | return 0; |
| 290 | } |
| 291 | |
| 292 | static int __init bsr_init(void) |
| 293 | { |
| 294 | struct device_node *np; |
| 295 | dev_t bsr_dev = MKDEV(bsr_major, 0); |
| 296 | int ret = -ENODEV; |
| 297 | int result; |
| 298 | |
| 299 | np = of_find_compatible_node(NULL, NULL, "ibm,bsr"); |
| 300 | if (!np) |
| 301 | goto out_err; |
| 302 | |
| 303 | bsr_class = class_create(THIS_MODULE, "bsr"); |
| 304 | if (IS_ERR(bsr_class)) { |
| 305 | printk(KERN_ERR "class_create() failed for bsr_class\n"); |
| 306 | goto out_err_1; |
| 307 | } |
| 308 | bsr_class->dev_attrs = bsr_dev_attrs; |
| 309 | |
| 310 | result = alloc_chrdev_region(&bsr_dev, 0, BSR_MAX_DEVS, "bsr"); |
| 311 | bsr_major = MAJOR(bsr_dev); |
| 312 | if (result < 0) { |
| 313 | printk(KERN_ERR "alloc_chrdev_region() failed for bsr\n"); |
| 314 | goto out_err_2; |
| 315 | } |
| 316 | |
| 317 | if ((ret = bsr_create_devs(np)) < 0) { |
| 318 | np = NULL; |
| 319 | goto out_err_3; |
| 320 | } |
| 321 | |
| 322 | return 0; |
| 323 | |
| 324 | out_err_3: |
| 325 | unregister_chrdev_region(bsr_dev, BSR_MAX_DEVS); |
| 326 | |
| 327 | out_err_2: |
| 328 | class_destroy(bsr_class); |
| 329 | |
| 330 | out_err_1: |
| 331 | of_node_put(np); |
| 332 | |
| 333 | out_err: |
| 334 | |
| 335 | return ret; |
| 336 | } |
| 337 | |
| 338 | static void __exit bsr_exit(void) |
| 339 | { |
| 340 | |
| 341 | bsr_cleanup_devs(); |
| 342 | |
| 343 | if (bsr_class) |
| 344 | class_destroy(bsr_class); |
| 345 | |
| 346 | if (bsr_major) |
| 347 | unregister_chrdev_region(MKDEV(bsr_major, 0), BSR_MAX_DEVS); |
| 348 | } |
| 349 | |
| 350 | module_init(bsr_init); |
| 351 | module_exit(bsr_exit); |
| 352 | MODULE_LICENSE("GPL"); |
| 353 | MODULE_AUTHOR("Sonny Rao <sonnyrao@us.ibm.com>"); |