linux/drivers/char/bsr.c
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   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
  57struct 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
  75static unsigned total_bsr_devs;
  76static struct list_head bsr_devs = LIST_HEAD_INIT(bsr_devs);
  77static struct class *bsr_class;
  78static int bsr_major;
  79
  80enum {
  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
  90static unsigned bsr_types[BSR_MAX];
  91
  92static ssize_t
  93bsr_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
  99static ssize_t
 100bsr_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
 106static ssize_t
 107bsr_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
 113static 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
 120static 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
 145static 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
 154static const struct file_operations bsr_fops = {
 155        .owner = THIS_MODULE,
 156        .mmap  = bsr_mmap,
 157        .open  = bsr_open,
 158        .llseek = noop_llseek,
 159};
 160
 161static 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
 175static 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
 280static 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
 295static 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
 341static 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
 353module_init(bsr_init);
 354module_exit(bsr_exit);
 355MODULE_LICENSE("GPL");
 356MODULE_AUTHOR("Sonny Rao <sonnyrao@us.ibm.com>");
 357
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