drivers/char/bsr.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* IBM POWER Barrier Synchronization Register Driver
   3  *
   4  * Copyright IBM Corporation 2008
   5  *
   6  * Author: Sonny Rao <sonnyrao@us.ibm.com>
   7  */
   8
   9 #include <linux/kernel.h>
  10 #include <linux/of.h>
  11 #include <linux/of_address.h>
  12 #include <linux/of_device.h>
  13 #include <linux/of_platform.h>
  14 #include <linux/fs.h>
  15 #include <linux/module.h>
  16 #include <linux/cdev.h>
  17 #include <linux/list.h>
  18 #include <linux/mm.h>
  19 #include <linux/slab.h>
  20 #include <asm/pgtable.h>
  21 #include <asm/io.h>
  22
  23 /*
  24  This driver exposes a special register which can be used for fast
  25  synchronization across a large SMP machine.  The hardware is exposed
  26  as an array of bytes where each process will write to one of the bytes to
  27  indicate it has finished the current stage and this update is broadcast to
  28  all processors without having to bounce a cacheline between them. In
  29  POWER5 and POWER6 there is one of these registers per SMP,  but it is
  30  presented in two forms; first, it is given as a whole and then as a number
  31  of smaller registers which alias to parts of the single whole register.
  32  This can potentially allow multiple groups of processes to each have their
  33  own private synchronization device.
  34
  35  Note that this hardware *must* be written to using *only* single byte writes.
  36  It may be read using 1, 2, 4, or 8 byte loads which must be aligned since
  37  this region is treated as cache-inhibited  processes should also use a
  38  full sync before and after writing to the BSR to ensure all stores and
  39  the BSR update have made it to all chips in the system
  40 */
  41
  42 /* This is arbitrary number, up to Power6 it's been 17 or fewer  */
  43 #define BSR_MAX_DEVS (32)
  44
  45 struct bsr_dev {
  46         u64      bsr_addr;     /* Real address */
  47         u64      bsr_len;      /* length of mem region we can map */
  48         unsigned bsr_bytes;    /* size of the BSR reg itself */
  49         unsigned bsr_stride;   /* interval at which BSR repeats in the page */
  50         unsigned bsr_type;     /* maps to enum below */
  51         unsigned bsr_num;      /* bsr id number for its type */
  52         int      bsr_minor;
  53
  54         struct list_head bsr_list;
  55
  56         dev_t    bsr_dev;
  57         struct cdev bsr_cdev;
  58         struct device *bsr_device;
  59         char     bsr_name[32];
  60
  61 };
  62
  63 static unsigned total_bsr_devs;
  64 static struct list_head bsr_devs = LIST_HEAD_INIT(bsr_devs);
  65 static struct class *bsr_class;
  66 static int bsr_major;
  67
  68 enum {
  69         BSR_8    = 0,
  70         BSR_16   = 1,
  71         BSR_64   = 2,
  72         BSR_128  = 3,
  73         BSR_4096 = 4,
  74         BSR_UNKNOWN = 5,
  75         BSR_MAX  = 6,
  76 };
  77
  78 static unsigned bsr_types[BSR_MAX];
  79
  80 static ssize_t
  81 bsr_size_show(struct device *dev, struct device_attribute *attr, char *buf)
  82 {
  83         struct bsr_dev *bsr_dev = dev_get_drvdata(dev);
  84         return sprintf(buf, "%u\n", bsr_dev->bsr_bytes);
  85 }
  86 static DEVICE_ATTR_RO(bsr_size);
  87
  88 static ssize_t
  89 bsr_stride_show(struct device *dev, struct device_attribute *attr, char *buf)
  90 {
  91         struct bsr_dev *bsr_dev = dev_get_drvdata(dev);
  92         return sprintf(buf, "%u\n", bsr_dev->bsr_stride);
  93 }
  94 static DEVICE_ATTR_RO(bsr_stride);
  95
  96 static ssize_t
  97 bsr_length_show(struct device *dev, struct device_attribute *attr, char *buf)
  98 {
  99         struct bsr_dev *bsr_dev = dev_get_drvdata(dev);
 100         return sprintf(buf, "%llu\n", bsr_dev->bsr_len);
 101 }
 102 static DEVICE_ATTR_RO(bsr_length);
 103
 104 static struct attribute *bsr_dev_attrs[] = {
 105         &dev_attr_bsr_size.attr,
 106         &dev_attr_bsr_stride.attr,
 107         &dev_attr_bsr_length.attr,
 108         NULL,
 109 };
 110 ATTRIBUTE_GROUPS(bsr_dev);
 111
 112 static int bsr_mmap(struct file *filp, struct vm_area_struct *vma)
 113 {
 114         unsigned long size   = vma->vm_end - vma->vm_start;
 115         struct bsr_dev *dev = filp->private_data;
 116         int ret;
 117
 118         vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
 119
 120         /* check for the case of a small BSR device and map one 4k page for it*/
 121         if (dev->bsr_len < PAGE_SIZE && size == PAGE_SIZE)
 122                 ret = remap_4k_pfn(vma, vma->vm_start, dev->bsr_addr >> 12,
 123                                    vma->vm_page_prot);
 124         else if (size <= dev->bsr_len)
 125                 ret = io_remap_pfn_range(vma, vma->vm_start,
 126                                          dev->bsr_addr >> PAGE_SHIFT,
 127                                          size, vma->vm_page_prot);
 128         else
 129                 return -EINVAL;
 130
 131         if (ret)
 132                 return -EAGAIN;
 133
 134         return 0;
 135 }
 136
 137 static int bsr_open(struct inode *inode, struct file *filp)
 138 {
 139         struct cdev *cdev = inode->i_cdev;
 140         struct bsr_dev *dev = container_of(cdev, struct bsr_dev, bsr_cdev);
 141
 142         filp->private_data = dev;
 143         return 0;
 144 }
 145
 146 static const struct file_operations bsr_fops = {
 147         .owner = THIS_MODULE,
 148         .mmap  = bsr_mmap,
 149         .open  = bsr_open,
 150         .llseek = noop_llseek,
 151 };
 152
 153 static void bsr_cleanup_devs(void)
 154 {
 155         struct bsr_dev *cur, *n;
 156
 157         list_for_each_entry_safe(cur, n, &bsr_devs, bsr_list) {
 158                 if (cur->bsr_device) {
 159                         cdev_del(&cur->bsr_cdev);
 160                         device_del(cur->bsr_device);
 161                 }
 162                 list_del(&cur->bsr_list);
 163                 kfree(cur);
 164         }
 165 }
 166
 167 static int bsr_add_node(struct device_node *bn)
 168 {
 169         int bsr_stride_len, bsr_bytes_len, num_bsr_devs;
 170         const u32 *bsr_stride;
 171         const u32 *bsr_bytes;
 172         unsigned i;
 173         int ret = -ENODEV;
 174
 175         bsr_stride = of_get_property(bn, "ibm,lock-stride", &bsr_stride_len);
 176         bsr_bytes  = of_get_property(bn, "ibm,#lock-bytes", &bsr_bytes_len);
 177
 178         if (!bsr_stride || !bsr_bytes ||
 179             (bsr_stride_len != bsr_bytes_len)) {
 180                 printk(KERN_ERR "bsr of-node has missing/incorrect property\n");
 181                 return ret;
 182         }
 183
 184         num_bsr_devs = bsr_bytes_len / sizeof(u32);
 185
 186         for (i = 0 ; i < num_bsr_devs; i++) {
 187                 struct bsr_dev *cur = kzalloc(sizeof(struct bsr_dev),
 188                                               GFP_KERNEL);
 189                 struct resource res;
 190                 int result;
 191
 192                 if (!cur) {
 193                         printk(KERN_ERR "Unable to alloc bsr dev\n");
 194                         ret = -ENOMEM;
 195                         goto out_err;
 196                 }
 197
 198                 result = of_address_to_resource(bn, i, &res);
 199                 if (result < 0) {
 200                         printk(KERN_ERR "bsr of-node has invalid reg property, skipping\n");
 201                         kfree(cur);
 202                         continue;
 203                 }
 204
 205                 cur->bsr_minor  = i + total_bsr_devs;
 206                 cur->bsr_addr   = res.start;
 207                 cur->bsr_len    = resource_size(&res);
 208                 cur->bsr_bytes  = bsr_bytes[i];
 209                 cur->bsr_stride = bsr_stride[i];
 210                 cur->bsr_dev    = MKDEV(bsr_major, i + total_bsr_devs);
 211
 212                 /* if we have a bsr_len of > 4k and less then PAGE_SIZE (64k pages) */
 213                 /* we can only map 4k of it, so only advertise the 4k in sysfs */
 214                 if (cur->bsr_len > 4096 && cur->bsr_len < PAGE_SIZE)
 215                         cur->bsr_len = 4096;
 216
 217                 switch(cur->bsr_bytes) {
 218                 case 8:
 219                         cur->bsr_type = BSR_8;
 220                         break;
 221                 case 16:
 222                         cur->bsr_type = BSR_16;
 223                         break;
 224                 case 64:
 225                         cur->bsr_type = BSR_64;
 226                         break;
 227                 case 128:
 228                         cur->bsr_type = BSR_128;
 229                         break;
 230                 case 4096:
 231                         cur->bsr_type = BSR_4096;
 232                         break;
 233                 default:
 234                         cur->bsr_type = BSR_UNKNOWN;
 235                 }
 236
 237                 cur->bsr_num = bsr_types[cur->bsr_type];
 238                 snprintf(cur->bsr_name, 32, "bsr%d_%d",
 239                          cur->bsr_bytes, cur->bsr_num);
 240
 241                 cdev_init(&cur->bsr_cdev, &bsr_fops);
 242                 result = cdev_add(&cur->bsr_cdev, cur->bsr_dev, 1);
 243                 if (result) {
 244                         kfree(cur);
 245                         goto out_err;
 246                 }
 247
 248                 cur->bsr_device = device_create(bsr_class, NULL, cur->bsr_dev,
 249                                                 cur, "%s", cur->bsr_name);
 250                 if (IS_ERR(cur->bsr_device)) {
 251                         printk(KERN_ERR "device_create failed for %s\n",
 252                                cur->bsr_name);
 253                         cdev_del(&cur->bsr_cdev);
 254                         kfree(cur);
 255                         goto out_err;
 256                 }
 257
 258                 bsr_types[cur->bsr_type] = cur->bsr_num + 1;
 259                 list_add_tail(&cur->bsr_list, &bsr_devs);
 260         }
 261
 262         total_bsr_devs += num_bsr_devs;
 263
 264         return 0;
 265
 266  out_err:
 267
 268         bsr_cleanup_devs();
 269         return ret;
 270 }
 271
 272 static int bsr_create_devs(struct device_node *bn)
 273 {
 274         int ret;
 275
 276         while (bn) {
 277                 ret = bsr_add_node(bn);
 278                 if (ret) {
 279                         of_node_put(bn);
 280                         return ret;
 281                 }
 282                 bn = of_find_compatible_node(bn, NULL, "ibm,bsr");
 283         }
 284         return 0;
 285 }
 286
 287 static int __init bsr_init(void)
 288 {
 289         struct device_node *np;
 290         dev_t bsr_dev;
 291         int ret = -ENODEV;
 292
 293         np = of_find_compatible_node(NULL, NULL, "ibm,bsr");
 294         if (!np)
 295                 goto out_err;
 296
 297         bsr_class = class_create(THIS_MODULE, "bsr");
 298         if (IS_ERR(bsr_class)) {
 299                 printk(KERN_ERR "class_create() failed for bsr_class\n");
 300                 ret = PTR_ERR(bsr_class);
 301                 goto out_err_1;
 302         }
 303         bsr_class->dev_groups = bsr_dev_groups;
 304
 305         ret = alloc_chrdev_region(&bsr_dev, 0, BSR_MAX_DEVS, "bsr");
 306         bsr_major = MAJOR(bsr_dev);
 307         if (ret < 0) {
 308                 printk(KERN_ERR "alloc_chrdev_region() failed for bsr\n");
 309                 goto out_err_2;
 310         }
 311
 312         ret = bsr_create_devs(np);
 313         if (ret < 0) {
 314                 np = NULL;
 315                 goto out_err_3;
 316         }
 317
 318         return 0;
 319
 320  out_err_3:
 321         unregister_chrdev_region(bsr_dev, BSR_MAX_DEVS);
 322
 323  out_err_2:
 324         class_destroy(bsr_class);
 325
 326  out_err_1:
 327         of_node_put(np);
 328
 329  out_err:
 330
 331         return ret;
 332 }
 333
 334 static void __exit  bsr_exit(void)
 335 {
 336
 337         bsr_cleanup_devs();
 338
 339         if (bsr_class)
 340                 class_destroy(bsr_class);
 341
 342         if (bsr_major)
 343                 unregister_chrdev_region(MKDEV(bsr_major, 0), BSR_MAX_DEVS);
 344 }
 345
 346 module_init(bsr_init);
 347 module_exit(bsr_exit);
 348 MODULE_LICENSE("GPL");
 349 MODULE_AUTHOR("Sonny Rao <sonnyrao@us.ibm.com>");