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_address.h>
  25 #include <linux/of_device.h>
  26 #include <linux/of_platform.h>
  27 #include <linux/fs.h>
  28 #include <linux/module.h>
  29 #include <linux/cdev.h>
  30 #include <linux/list.h>
  31 #include <linux/mm.h>
  32 #include <linux/slab.h>
  33 #include <asm/pgtable.h>
  34 #include <asm/io.h>
  35
  36 /*
  37  This driver exposes a special register which can be used for fast
  38  synchronization across a large SMP machine.  The hardware is exposed
  39  as an array of bytes where each process will write to one of the bytes to
  40  indicate it has finished the current stage and this update is broadcast to
  41  all processors without having to bounce a cacheline between them. In
  42  POWER5 and POWER6 there is one of these registers per SMP,  but it is
  43  presented in two forms; first, it is given as a whole and then as a number
  44  of smaller registers which alias to parts of the single whole register.
  45  This can potentially allow multiple groups of processes to each have their
  46  own private synchronization device.
  47
  48  Note that this hardware *must* be written to using *only* single byte writes.
  49  It may be read using 1, 2, 4, or 8 byte loads which must be aligned since
  50  this region is treated as cache-inhibited  processes should also use a
  51  full sync before and after writing to the BSR to ensure all stores and
  52  the BSR update have made it to all chips in the system
  53 */
  54
  55 /* This is arbitrary number, up to Power6 it's been 17 or fewer  */
  56 #define BSR_MAX_DEVS (32)
  57
  58 struct bsr_dev {
  59         u64      bsr_addr;     /* Real address */
  60         u64      bsr_len;      /* length of mem region we can map */
  61         unsigned bsr_bytes;    /* size of the BSR reg itself */
  62         unsigned bsr_stride;   /* interval at which BSR repeats in the page */
  63         unsigned bsr_type;     /* maps to enum below */
  64         unsigned bsr_num;      /* bsr id number for its type */
  65         int      bsr_minor;
  66
  67         struct list_head bsr_list;
  68
  69         dev_t    bsr_dev;
  70         struct cdev bsr_cdev;
  71         struct device *bsr_device;
  72         char     bsr_name[32];
  73
  74 };
  75
  76 static unsigned total_bsr_devs;
  77 static struct list_head bsr_devs = LIST_HEAD_INIT(bsr_devs);
  78 static struct class *bsr_class;
  79 static int bsr_major;
  80
  81 enum {
  82         BSR_8    = 0,
  83         BSR_16   = 1,
  84         BSR_64   = 2,
  85         BSR_128  = 3,
  86         BSR_4096 = 4,
  87         BSR_UNKNOWN = 5,
  88         BSR_MAX  = 6,
  89 };
  90
  91 static unsigned bsr_types[BSR_MAX];
  92
  93 static ssize_t
  94 bsr_size_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, "%u\n", bsr_dev->bsr_bytes);
  98 }
  99 static DEVICE_ATTR_RO(bsr_size);
 100
 101 static ssize_t
 102 bsr_stride_show(struct device *dev, struct device_attribute *attr, char *buf)
 103 {
 104         struct bsr_dev *bsr_dev = dev_get_drvdata(dev);
 105         return sprintf(buf, "%u\n", bsr_dev->bsr_stride);
 106 }
 107 static DEVICE_ATTR_RO(bsr_stride);
 108
 109 static ssize_t
 110 bsr_length_show(struct device *dev, struct device_attribute *attr, char *buf)
 111 {
 112         struct bsr_dev *bsr_dev = dev_get_drvdata(dev);
 113         return sprintf(buf, "%llu\n", bsr_dev->bsr_len);
 114 }
 115 static DEVICE_ATTR_RO(bsr_length);
 116
 117 static struct attribute *bsr_dev_attrs[] = {
 118         &dev_attr_bsr_size.attr,
 119         &dev_attr_bsr_stride.attr,
 120         &dev_attr_bsr_length.attr,
 121         NULL,
 122 };
 123 ATTRIBUTE_GROUPS(bsr_dev);
 124
 125 static int bsr_mmap(struct file *filp, struct vm_area_struct *vma)
 126 {
 127         unsigned long size   = vma->vm_end - vma->vm_start;
 128         struct bsr_dev *dev = filp->private_data;
 129         int ret;
 130
 131         vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
 132
 133         /* check for the case of a small BSR device and map one 4k page for it*/
 134         if (dev->bsr_len < PAGE_SIZE && size == PAGE_SIZE)
 135                 ret = remap_4k_pfn(vma, vma->vm_start, dev->bsr_addr >> 12,
 136                                    vma->vm_page_prot);
 137         else if (size <= dev->bsr_len)
 138                 ret = io_remap_pfn_range(vma, vma->vm_start,
 139                                          dev->bsr_addr >> PAGE_SHIFT,
 140                                          size, vma->vm_page_prot);
 141         else
 142                 return -EINVAL;
 143
 144         if (ret)
 145                 return -EAGAIN;
 146
 147         return 0;
 148 }
 149
 150 static int bsr_open(struct inode * inode, struct file * filp)
 151 {
 152         struct cdev *cdev = inode->i_cdev;
 153         struct bsr_dev *dev = container_of(cdev, struct bsr_dev, bsr_cdev);
 154
 155         filp->private_data = dev;
 156         return 0;
 157 }
 158
 159 static const struct file_operations bsr_fops = {
 160         .owner = THIS_MODULE,
 161         .mmap  = bsr_mmap,
 162         .open  = bsr_open,
 163         .llseek = noop_llseek,
 164 };
 165
 166 static void bsr_cleanup_devs(void)
 167 {
 168         struct bsr_dev *cur, *n;
 169
 170         list_for_each_entry_safe(cur, n, &bsr_devs, bsr_list) {
 171                 if (cur->bsr_device) {
 172                         cdev_del(&cur->bsr_cdev);
 173                         device_del(cur->bsr_device);
 174                 }
 175                 list_del(&cur->bsr_list);
 176                 kfree(cur);
 177         }
 178 }
 179
 180 static int bsr_add_node(struct device_node *bn)
 181 {
 182         int bsr_stride_len, bsr_bytes_len, num_bsr_devs;
 183         const u32 *bsr_stride;
 184         const u32 *bsr_bytes;
 185         unsigned i;
 186         int ret = -ENODEV;
 187
 188         bsr_stride = of_get_property(bn, "ibm,lock-stride", &bsr_stride_len);
 189         bsr_bytes  = of_get_property(bn, "ibm,#lock-bytes", &bsr_bytes_len);
 190
 191         if (!bsr_stride || !bsr_bytes ||
 192             (bsr_stride_len != bsr_bytes_len)) {
 193                 printk(KERN_ERR "bsr of-node has missing/incorrect property\n");
 194                 return ret;
 195         }
 196
 197         num_bsr_devs = bsr_bytes_len / sizeof(u32);
 198
 199         for (i = 0 ; i < num_bsr_devs; i++) {
 200                 struct bsr_dev *cur = kzalloc(sizeof(struct bsr_dev),
 201                                               GFP_KERNEL);
 202                 struct resource res;
 203                 int result;
 204
 205                 if (!cur) {
 206                         printk(KERN_ERR "Unable to alloc bsr dev\n");
 207                         ret = -ENOMEM;
 208                         goto out_err;
 209                 }
 210
 211                 result = of_address_to_resource(bn, i, &res);
 212                 if (result < 0) {
 213                         printk(KERN_ERR "bsr of-node has invalid reg property, skipping\n");
 214                         kfree(cur);
 215                         continue;
 216                 }
 217
 218                 cur->bsr_minor  = i + total_bsr_devs;
 219                 cur->bsr_addr   = res.start;
 220                 cur->bsr_len    = resource_size(&res);
 221                 cur->bsr_bytes  = bsr_bytes[i];
 222                 cur->bsr_stride = bsr_stride[i];
 223                 cur->bsr_dev    = MKDEV(bsr_major, i + total_bsr_devs);
 224
 225                 /* if we have a bsr_len of > 4k and less then PAGE_SIZE (64k pages) */
 226                 /* we can only map 4k of it, so only advertise the 4k in sysfs */
 227                 if (cur->bsr_len > 4096 && cur->bsr_len < PAGE_SIZE)
 228                         cur->bsr_len = 4096;
 229
 230                 switch(cur->bsr_bytes) {
 231                 case 8:
 232                         cur->bsr_type = BSR_8;
 233                         break;
 234                 case 16:
 235                         cur->bsr_type = BSR_16;
 236                         break;
 237                 case 64:
 238                         cur->bsr_type = BSR_64;
 239                         break;
 240                 case 128:
 241                         cur->bsr_type = BSR_128;
 242                         break;
 243                 case 4096:
 244                         cur->bsr_type = BSR_4096;
 245                         break;
 246                 default:
 247                         cur->bsr_type = BSR_UNKNOWN;
 248                 }
 249
 250                 cur->bsr_num = bsr_types[cur->bsr_type];
 251                 snprintf(cur->bsr_name, 32, "bsr%d_%d",
 252                          cur->bsr_bytes, cur->bsr_num);
 253
 254                 cdev_init(&cur->bsr_cdev, &bsr_fops);
 255                 result = cdev_add(&cur->bsr_cdev, cur->bsr_dev, 1);
 256                 if (result) {
 257                         kfree(cur);
 258                         goto out_err;
 259                 }
 260
 261                 cur->bsr_device = device_create(bsr_class, NULL, cur->bsr_dev,
 262                                                 cur, "%s", cur->bsr_name);
 263                 if (IS_ERR(cur->bsr_device)) {
 264                         printk(KERN_ERR "device_create failed for %s\n",
 265                                cur->bsr_name);
 266                         cdev_del(&cur->bsr_cdev);
 267                         kfree(cur);
 268                         goto out_err;
 269                 }
 270
 271                 bsr_types[cur->bsr_type] = cur->bsr_num + 1;
 272                 list_add_tail(&cur->bsr_list, &bsr_devs);
 273         }
 274
 275         total_bsr_devs += num_bsr_devs;
 276
 277         return 0;
 278
 279  out_err:
 280
 281         bsr_cleanup_devs();
 282         return ret;
 283 }
 284
 285 static int bsr_create_devs(struct device_node *bn)
 286 {
 287         int ret;
 288
 289         while (bn) {
 290                 ret = bsr_add_node(bn);
 291                 if (ret) {
 292                         of_node_put(bn);
 293                         return ret;
 294                 }
 295                 bn = of_find_compatible_node(bn, NULL, "ibm,bsr");
 296         }
 297         return 0;
 298 }
 299
 300 static int __init bsr_init(void)
 301 {
 302         struct device_node *np;
 303         dev_t bsr_dev;
 304         int ret = -ENODEV;
 305
 306         np = of_find_compatible_node(NULL, NULL, "ibm,bsr");
 307         if (!np)
 308                 goto out_err;
 309
 310         bsr_class = class_create(THIS_MODULE, "bsr");
 311         if (IS_ERR(bsr_class)) {
 312                 printk(KERN_ERR "class_create() failed for bsr_class\n");
 313                 ret = PTR_ERR(bsr_class);
 314                 goto out_err_1;
 315         }
 316         bsr_class->dev_groups = bsr_dev_groups;
 317
 318         ret = alloc_chrdev_region(&bsr_dev, 0, BSR_MAX_DEVS, "bsr");
 319         bsr_major = MAJOR(bsr_dev);
 320         if (ret < 0) {
 321                 printk(KERN_ERR "alloc_chrdev_region() failed for bsr\n");
 322                 goto out_err_2;
 323         }
 324
 325         if ((ret = bsr_create_devs(np)) < 0) {
 326                 np = NULL;
 327                 goto out_err_3;
 328         }
 329
 330         return 0;
 331
 332  out_err_3:
 333         unregister_chrdev_region(bsr_dev, BSR_MAX_DEVS);
 334
 335  out_err_2:
 336         class_destroy(bsr_class);
 337
 338  out_err_1:
 339         of_node_put(np);
 340
 341  out_err:
 342
 343         return ret;
 344 }
 345
 346 static void __exit  bsr_exit(void)
 347 {
 348
 349         bsr_cleanup_devs();
 350
 351         if (bsr_class)
 352                 class_destroy(bsr_class);
 353
 354         if (bsr_major)
 355                 unregister_chrdev_region(MKDEV(bsr_major, 0), BSR_MAX_DEVS);
 356 }
 357
 358 module_init(bsr_init);
 359 module_exit(bsr_exit);
 360 MODULE_LICENSE("GPL");
 361 MODULE_AUTHOR("Sonny Rao <sonnyrao@us.ibm.com>");