drivers/char/bsr.c

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