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 };
 159
 160 static void bsr_cleanup_devs(void)
 161 {
 162         struct bsr_dev *cur, *n;
 163
 164         list_for_each_entry_safe(cur, n, &bsr_devs, bsr_list) {
 165                 if (cur->bsr_device) {
 166                         cdev_del(&cur->bsr_cdev);
 167                         device_del(cur->bsr_device);
 168                 }
 169                 list_del(&cur->bsr_list);
 170                 kfree(cur);
 171         }
 172 }
 173
 174 static int bsr_add_node(struct device_node *bn)
 175 {
 176         int bsr_stride_len, bsr_bytes_len, num_bsr_devs;
 177         const u32 *bsr_stride;
 178         const u32 *bsr_bytes;
 179         unsigned i;
 180         int ret = -ENODEV;
 181
 182         bsr_stride = of_get_property(bn, "ibm,lock-stride", &bsr_stride_len);
 183         bsr_bytes  = of_get_property(bn, "ibm,#lock-bytes", &bsr_bytes_len);
 184
 185         if (!bsr_stride || !bsr_bytes ||
 186             (bsr_stride_len != bsr_bytes_len)) {
 187                 printk(KERN_ERR "bsr of-node has missing/incorrect property\n");
 188                 return ret;
 189         }
 190
 191         num_bsr_devs = bsr_bytes_len / sizeof(u32);
 192
 193         for (i = 0 ; i < num_bsr_devs; i++) {
 194                 struct bsr_dev *cur = kzalloc(sizeof(struct bsr_dev),
 195                                               GFP_KERNEL);
 196                 struct resource res;
 197                 int result;
 198
 199                 if (!cur) {
 200                         printk(KERN_ERR "Unable to alloc bsr dev\n");
 201                         ret = -ENOMEM;
 202                         goto out_err;
 203                 }
 204
 205                 result = of_address_to_resource(bn, i, &res);
 206                 if (result < 0) {
 207                         printk(KERN_ERR "bsr of-node has invalid reg property, skipping\n");
 208                         kfree(cur);
 209                         continue;
 210                 }
 211
 212                 cur->bsr_minor  = i + total_bsr_devs;
 213                 cur->bsr_addr   = res.start;
 214                 cur->bsr_len    = res.end - res.start + 1;
 215                 cur->bsr_bytes  = bsr_bytes[i];
 216                 cur->bsr_stride = bsr_stride[i];
 217                 cur->bsr_dev    = MKDEV(bsr_major, i + total_bsr_devs);
 218
 219                 /* if we have a bsr_len of > 4k and less then PAGE_SIZE (64k pages) */
 220                 /* we can only map 4k of it, so only advertise the 4k in sysfs */
 221                 if (cur->bsr_len > 4096 && cur->bsr_len < PAGE_SIZE)
 222                         cur->bsr_len = 4096;
 223
 224                 switch(cur->bsr_bytes) {
 225                 case 8:
 226                         cur->bsr_type = BSR_8;
 227                         break;
 228                 case 16:
 229                         cur->bsr_type = BSR_16;
 230                         break;
 231                 case 64:
 232                         cur->bsr_type = BSR_64;
 233                         break;
 234                 case 128:
 235                         cur->bsr_type = BSR_128;
 236                         break;
 237                 case 4096:
 238                         cur->bsr_type = BSR_4096;
 239                         break;
 240                 default:
 241                         cur->bsr_type = BSR_UNKNOWN;
 242                 }
 243
 244                 cur->bsr_num = bsr_types[cur->bsr_type];
 245                 snprintf(cur->bsr_name, 32, "bsr%d_%d",
 246                          cur->bsr_bytes, cur->bsr_num);
 247
 248                 cdev_init(&cur->bsr_cdev, &bsr_fops);
 249                 result = cdev_add(&cur->bsr_cdev, cur->bsr_dev, 1);
 250                 if (result) {
 251                         kfree(cur);
 252                         goto out_err;
 253                 }
 254
 255                 cur->bsr_device = device_create(bsr_class, NULL, cur->bsr_dev,
 256                                                 cur, cur->bsr_name);
 257                 if (IS_ERR(cur->bsr_device)) {
 258                         printk(KERN_ERR "device_create failed for %s\n",
 259                                cur->bsr_name);
 260                         cdev_del(&cur->bsr_cdev);
 261                         kfree(cur);
 262                         goto out_err;
 263                 }
 264
 265                 bsr_types[cur->bsr_type] = cur->bsr_num + 1;
 266                 list_add_tail(&cur->bsr_list, &bsr_devs);
 267         }
 268
 269         total_bsr_devs += num_bsr_devs;
 270
 271         return 0;
 272
 273  out_err:
 274
 275         bsr_cleanup_devs();
 276         return ret;
 277 }
 278
 279 static int bsr_create_devs(struct device_node *bn)
 280 {
 281         int ret;
 282
 283         while (bn) {
 284                 ret = bsr_add_node(bn);
 285                 if (ret) {
 286                         of_node_put(bn);
 287                         return ret;
 288                 }
 289                 bn = of_find_compatible_node(bn, NULL, "ibm,bsr");
 290         }
 291         return 0;
 292 }
 293
 294 static int __init bsr_init(void)
 295 {
 296         struct device_node *np;
 297         dev_t bsr_dev = MKDEV(bsr_major, 0);
 298         int ret = -ENODEV;
 299         int result;
 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                 goto out_err_1;
 309         }
 310         bsr_class->dev_attrs = bsr_dev_attrs;
 311
 312         result = alloc_chrdev_region(&bsr_dev, 0, BSR_MAX_DEVS, "bsr");
 313         bsr_major = MAJOR(bsr_dev);
 314         if (result < 0) {
 315                 printk(KERN_ERR "alloc_chrdev_region() failed for bsr\n");
 316                 goto out_err_2;
 317         }
 318
 319         if ((ret = bsr_create_devs(np)) < 0) {
 320                 np = NULL;
 321                 goto out_err_3;
 322         }
 323
 324         return 0;
 325
 326  out_err_3:
 327         unregister_chrdev_region(bsr_dev, BSR_MAX_DEVS);
 328
 329  out_err_2:
 330         class_destroy(bsr_class);
 331
 332  out_err_1:
 333         of_node_put(np);
 334
 335  out_err:
 336
 337         return ret;
 338 }
 339
 340 static void __exit  bsr_exit(void)
 341 {
 342
 343         bsr_cleanup_devs();
 344
 345         if (bsr_class)
 346                 class_destroy(bsr_class);
 347
 348         if (bsr_major)
 349                 unregister_chrdev_region(MKDEV(bsr_major, 0), BSR_MAX_DEVS);
 350 }
 351
 352 module_init(bsr_init);
 353 module_exit(bsr_exit);
 354 MODULE_LICENSE("GPL");
 355 MODULE_AUTHOR("Sonny Rao <sonnyrao@us.ibm.com>");