drivers/pci/access.c

   1 #include <linux/delay.h>
   2 #include <linux/pci.h>
   3 #include <linux/module.h>
   4 #include <linux/sched.h>
   5 #include <linux/slab.h>
   6 #include <linux/ioport.h>
   7 #include <linux/wait.h>
   8
   9 #include "pci.h"
  10
  11 /*
  12  * This interrupt-safe spinlock protects all accesses to PCI
  13  * configuration space.
  14  */
  15
  16 DEFINE_RAW_SPINLOCK(pci_lock);
  17
  18 /*
  19  *  Wrappers for all PCI configuration access functions.  They just check
  20  *  alignment, do locking and call the low-level functions pointed to
  21  *  by pci_dev->ops.
  22  */
  23
  24 #define PCI_byte_BAD 0
  25 #define PCI_word_BAD (pos & 1)
  26 #define PCI_dword_BAD (pos & 3)
  27
  28 #define PCI_OP_READ(size,type,len) \
  29 int pci_bus_read_config_##size \
  30         (struct pci_bus *bus, unsigned int devfn, int pos, type *value) \
  31 {                                                                       \
  32         int res;                                                        \
  33         unsigned long flags;                                            \
  34         u32 data = 0;                                                   \
  35         if (PCI_##size##_BAD) return PCIBIOS_BAD_REGISTER_NUMBER;       \
  36         raw_spin_lock_irqsave(&pci_lock, flags);                        \
  37         res = bus->ops->read(bus, devfn, pos, len, &data);              \
  38         *value = (type)data;                                            \
  39         raw_spin_unlock_irqrestore(&pci_lock, flags);           \
  40         return res;                                                     \
  41 }
  42
  43 #define PCI_OP_WRITE(size,type,len) \
  44 int pci_bus_write_config_##size \
  45         (struct pci_bus *bus, unsigned int devfn, int pos, type value)  \
  46 {                                                                       \
  47         int res;                                                        \
  48         unsigned long flags;                                            \
  49         if (PCI_##size##_BAD) return PCIBIOS_BAD_REGISTER_NUMBER;       \
  50         raw_spin_lock_irqsave(&pci_lock, flags);                        \
  51         res = bus->ops->write(bus, devfn, pos, len, value);             \
  52         raw_spin_unlock_irqrestore(&pci_lock, flags);           \
  53         return res;                                                     \
  54 }
  55
  56 PCI_OP_READ(byte, u8, 1)
  57 PCI_OP_READ(word, u16, 2)
  58 PCI_OP_READ(dword, u32, 4)
  59 PCI_OP_WRITE(byte, u8, 1)
  60 PCI_OP_WRITE(word, u16, 2)
  61 PCI_OP_WRITE(dword, u32, 4)
  62
  63 EXPORT_SYMBOL(pci_bus_read_config_byte);
  64 EXPORT_SYMBOL(pci_bus_read_config_word);
  65 EXPORT_SYMBOL(pci_bus_read_config_dword);
  66 EXPORT_SYMBOL(pci_bus_write_config_byte);
  67 EXPORT_SYMBOL(pci_bus_write_config_word);
  68 EXPORT_SYMBOL(pci_bus_write_config_dword);
  69
  70 /**
  71  * pci_bus_set_ops - Set raw operations of pci bus
  72  * @bus:        pci bus struct
  73  * @ops:        new raw operations
  74  *
  75  * Return previous raw operations
  76  */
  77 struct pci_ops *pci_bus_set_ops(struct pci_bus *bus, struct pci_ops *ops)
  78 {
  79         struct pci_ops *old_ops;
  80         unsigned long flags;
  81
  82         raw_spin_lock_irqsave(&pci_lock, flags);
  83         old_ops = bus->ops;
  84         bus->ops = ops;
  85         raw_spin_unlock_irqrestore(&pci_lock, flags);
  86         return old_ops;
  87 }
  88 EXPORT_SYMBOL(pci_bus_set_ops);
  89
  90 /**
  91  * pci_read_vpd - Read one entry from Vital Product Data
  92  * @dev:        pci device struct
  93  * @pos:        offset in vpd space
  94  * @count:      number of bytes to read
  95  * @buf:        pointer to where to store result
  96  *
  97  */
  98 ssize_t pci_read_vpd(struct pci_dev *dev, loff_t pos, size_t count, void *buf)
  99 {
 100         if (!dev->vpd || !dev->vpd->ops)
 101                 return -ENODEV;
 102         return dev->vpd->ops->read(dev, pos, count, buf);
 103 }
 104 EXPORT_SYMBOL(pci_read_vpd);
 105
 106 /**
 107  * pci_write_vpd - Write entry to Vital Product Data
 108  * @dev:        pci device struct
 109  * @pos:        offset in vpd space
 110  * @count:      number of bytes to write
 111  * @buf:        buffer containing write data
 112  *
 113  */
 114 ssize_t pci_write_vpd(struct pci_dev *dev, loff_t pos, size_t count, const void *buf)
 115 {
 116         if (!dev->vpd || !dev->vpd->ops)
 117                 return -ENODEV;
 118         return dev->vpd->ops->write(dev, pos, count, buf);
 119 }
 120 EXPORT_SYMBOL(pci_write_vpd);
 121
 122 /*
 123  * The following routines are to prevent the user from accessing PCI config
 124  * space when it's unsafe to do so.  Some devices require this during BIST and
 125  * we're required to prevent it during D-state transitions.
 126  *
 127  * We have a bit per device to indicate it's blocked and a global wait queue
 128  * for callers to sleep on until devices are unblocked.
 129  */
 130 static DECLARE_WAIT_QUEUE_HEAD(pci_cfg_wait);
 131
 132 static noinline void pci_wait_cfg(struct pci_dev *dev)
 133 {
 134         DECLARE_WAITQUEUE(wait, current);
 135
 136         __add_wait_queue(&pci_cfg_wait, &wait);
 137         do {
 138                 set_current_state(TASK_UNINTERRUPTIBLE);
 139                 raw_spin_unlock_irq(&pci_lock);
 140                 schedule();
 141                 raw_spin_lock_irq(&pci_lock);
 142         } while (dev->block_cfg_access);
 143         __remove_wait_queue(&pci_cfg_wait, &wait);
 144 }
 145
 146 /* Returns 0 on success, negative values indicate error. */
 147 #define PCI_USER_READ_CONFIG(size,type)                                 \
 148 int pci_user_read_config_##size                                         \
 149         (struct pci_dev *dev, int pos, type *val)                       \
 150 {                                                                       \
 151         int ret = PCIBIOS_SUCCESSFUL;                                   \
 152         u32 data = -1;                                                  \
 153         if (PCI_##size##_BAD)                                           \
 154                 return -EINVAL;                                         \
 155         raw_spin_lock_irq(&pci_lock);                           \
 156         if (unlikely(dev->block_cfg_access))                            \
 157                 pci_wait_cfg(dev);                                      \
 158         ret = dev->bus->ops->read(dev->bus, dev->devfn,                 \
 159                                         pos, sizeof(type), &data);      \
 160         raw_spin_unlock_irq(&pci_lock);                         \
 161         *val = (type)data;                                              \
 162         return pcibios_err_to_errno(ret);                               \
 163 }                                                                       \
 164 EXPORT_SYMBOL_GPL(pci_user_read_config_##size);
 165
 166 /* Returns 0 on success, negative values indicate error. */
 167 #define PCI_USER_WRITE_CONFIG(size,type)                                \
 168 int pci_user_write_config_##size                                        \
 169         (struct pci_dev *dev, int pos, type val)                        \
 170 {                                                                       \
 171         int ret = PCIBIOS_SUCCESSFUL;                                   \
 172         if (PCI_##size##_BAD)                                           \
 173                 return -EINVAL;                                         \
 174         raw_spin_lock_irq(&pci_lock);                           \
 175         if (unlikely(dev->block_cfg_access))                            \
 176                 pci_wait_cfg(dev);                                      \
 177         ret = dev->bus->ops->write(dev->bus, dev->devfn,                \
 178                                         pos, sizeof(type), val);        \
 179         raw_spin_unlock_irq(&pci_lock);                         \
 180         return pcibios_err_to_errno(ret);                               \
 181 }                                                                       \
 182 EXPORT_SYMBOL_GPL(pci_user_write_config_##size);
 183
 184 PCI_USER_READ_CONFIG(byte, u8)
 185 PCI_USER_READ_CONFIG(word, u16)
 186 PCI_USER_READ_CONFIG(dword, u32)
 187 PCI_USER_WRITE_CONFIG(byte, u8)
 188 PCI_USER_WRITE_CONFIG(word, u16)
 189 PCI_USER_WRITE_CONFIG(dword, u32)
 190
 191 /* VPD access through PCI 2.2+ VPD capability */
 192
 193 #define PCI_VPD_PCI22_SIZE (PCI_VPD_ADDR_MASK + 1)
 194
 195 struct pci_vpd_pci22 {
 196         struct pci_vpd base;
 197         struct mutex lock;
 198         u16     flag;
 199         bool    busy;
 200         u8      cap;
 201 };
 202
 203 /*
 204  * Wait for last operation to complete.
 205  * This code has to spin since there is no other notification from the PCI
 206  * hardware. Since the VPD is often implemented by serial attachment to an
 207  * EEPROM, it may take many milliseconds to complete.
 208  *
 209  * Returns 0 on success, negative values indicate error.
 210  */
 211 static int pci_vpd_pci22_wait(struct pci_dev *dev)
 212 {
 213         struct pci_vpd_pci22 *vpd =
 214                 container_of(dev->vpd, struct pci_vpd_pci22, base);
 215         unsigned long timeout = jiffies + HZ/20 + 2;
 216         u16 status;
 217         int ret;
 218
 219         if (!vpd->busy)
 220                 return 0;
 221
 222         for (;;) {
 223                 ret = pci_user_read_config_word(dev, vpd->cap + PCI_VPD_ADDR,
 224                                                 &status);
 225                 if (ret < 0)
 226                         return ret;
 227
 228                 if ((status & PCI_VPD_ADDR_F) == vpd->flag) {
 229                         vpd->busy = false;
 230                         return 0;
 231                 }
 232
 233                 if (time_after(jiffies, timeout)) {
 234                         dev_printk(KERN_DEBUG, &dev->dev,
 235                                    "vpd r/w failed.  This is likely a firmware "
 236                                    "bug on this device.  Contact the card "
 237                                    "vendor for a firmware update.");
 238                         return -ETIMEDOUT;
 239                 }
 240                 if (fatal_signal_pending(current))
 241                         return -EINTR;
 242                 if (!cond_resched())
 243                         udelay(10);
 244         }
 245 }
 246
 247 static ssize_t pci_vpd_pci22_read(struct pci_dev *dev, loff_t pos, size_t count,
 248                                   void *arg)
 249 {
 250         struct pci_vpd_pci22 *vpd =
 251                 container_of(dev->vpd, struct pci_vpd_pci22, base);
 252         int ret;
 253         loff_t end = pos + count;
 254         u8 *buf = arg;
 255
 256         if (pos < 0 || pos > vpd->base.len || end > vpd->base.len)
 257                 return -EINVAL;
 258
 259         if (mutex_lock_killable(&vpd->lock))
 260                 return -EINTR;
 261
 262         ret = pci_vpd_pci22_wait(dev);
 263         if (ret < 0)
 264                 goto out;
 265
 266         while (pos < end) {
 267                 u32 val;
 268                 unsigned int i, skip;
 269
 270                 ret = pci_user_write_config_word(dev, vpd->cap + PCI_VPD_ADDR,
 271                                                  pos & ~3);
 272                 if (ret < 0)
 273                         break;
 274                 vpd->busy = true;
 275                 vpd->flag = PCI_VPD_ADDR_F;
 276                 ret = pci_vpd_pci22_wait(dev);
 277                 if (ret < 0)
 278                         break;
 279
 280                 ret = pci_user_read_config_dword(dev, vpd->cap + PCI_VPD_DATA, &val);
 281                 if (ret < 0)
 282                         break;
 283
 284                 skip = pos & 3;
 285                 for (i = 0;  i < sizeof(u32); i++) {
 286                         if (i >= skip) {
 287                                 *buf++ = val;
 288                                 if (++pos == end)
 289                                         break;
 290                         }
 291                         val >>= 8;
 292                 }
 293         }
 294 out:
 295         mutex_unlock(&vpd->lock);
 296         return ret ? ret : count;
 297 }
 298
 299 static ssize_t pci_vpd_pci22_write(struct pci_dev *dev, loff_t pos, size_t count,
 300                                    const void *arg)
 301 {
 302         struct pci_vpd_pci22 *vpd =
 303                 container_of(dev->vpd, struct pci_vpd_pci22, base);
 304         const u8 *buf = arg;
 305         loff_t end = pos + count;
 306         int ret = 0;
 307
 308         if (pos < 0 || (pos & 3) || (count & 3) || end > vpd->base.len)
 309                 return -EINVAL;
 310
 311         if (mutex_lock_killable(&vpd->lock))
 312                 return -EINTR;
 313
 314         ret = pci_vpd_pci22_wait(dev);
 315         if (ret < 0)
 316                 goto out;
 317
 318         while (pos < end) {
 319                 u32 val;
 320
 321                 val = *buf++;
 322                 val |= *buf++ << 8;
 323                 val |= *buf++ << 16;
 324                 val |= *buf++ << 24;
 325
 326                 ret = pci_user_write_config_dword(dev, vpd->cap + PCI_VPD_DATA, val);
 327                 if (ret < 0)
 328                         break;
 329                 ret = pci_user_write_config_word(dev, vpd->cap + PCI_VPD_ADDR,
 330                                                  pos | PCI_VPD_ADDR_F);
 331                 if (ret < 0)
 332                         break;
 333
 334                 vpd->busy = true;
 335                 vpd->flag = 0;
 336                 ret = pci_vpd_pci22_wait(dev);
 337                 if (ret < 0)
 338                         break;
 339
 340                 pos += sizeof(u32);
 341         }
 342 out:
 343         mutex_unlock(&vpd->lock);
 344         return ret ? ret : count;
 345 }
 346
 347 static void pci_vpd_pci22_release(struct pci_dev *dev)
 348 {
 349         kfree(container_of(dev->vpd, struct pci_vpd_pci22, base));
 350 }
 351
 352 static const struct pci_vpd_ops pci_vpd_pci22_ops = {
 353         .read = pci_vpd_pci22_read,
 354         .write = pci_vpd_pci22_write,
 355         .release = pci_vpd_pci22_release,
 356 };
 357
 358 int pci_vpd_pci22_init(struct pci_dev *dev)
 359 {
 360         struct pci_vpd_pci22 *vpd;
 361         u8 cap;
 362
 363         cap = pci_find_capability(dev, PCI_CAP_ID_VPD);
 364         if (!cap)
 365                 return -ENODEV;
 366         vpd = kzalloc(sizeof(*vpd), GFP_ATOMIC);
 367         if (!vpd)
 368                 return -ENOMEM;
 369
 370         vpd->base.len = PCI_VPD_PCI22_SIZE;
 371         vpd->base.ops = &pci_vpd_pci22_ops;
 372         mutex_init(&vpd->lock);
 373         vpd->cap = cap;
 374         vpd->busy = false;
 375         dev->vpd = &vpd->base;
 376         return 0;
 377 }
 378
 379 /**
 380  * pci_cfg_access_lock - Lock PCI config reads/writes
 381  * @dev:        pci device struct
 382  *
 383  * When access is locked, any userspace reads or writes to config
 384  * space and concurrent lock requests will sleep until access is
 385  * allowed via pci_cfg_access_unlocked again.
 386  */
 387 void pci_cfg_access_lock(struct pci_dev *dev)
 388 {
 389         might_sleep();
 390
 391         raw_spin_lock_irq(&pci_lock);
 392         if (dev->block_cfg_access)
 393                 pci_wait_cfg(dev);
 394         dev->block_cfg_access = 1;
 395         raw_spin_unlock_irq(&pci_lock);
 396 }
 397 EXPORT_SYMBOL_GPL(pci_cfg_access_lock);
 398
 399 /**
 400  * pci_cfg_access_trylock - try to lock PCI config reads/writes
 401  * @dev:        pci device struct
 402  *
 403  * Same as pci_cfg_access_lock, but will return 0 if access is
 404  * already locked, 1 otherwise. This function can be used from
 405  * atomic contexts.
 406  */
 407 bool pci_cfg_access_trylock(struct pci_dev *dev)
 408 {
 409         unsigned long flags;
 410         bool locked = true;
 411
 412         raw_spin_lock_irqsave(&pci_lock, flags);
 413         if (dev->block_cfg_access)
 414                 locked = false;
 415         else
 416                 dev->block_cfg_access = 1;
 417         raw_spin_unlock_irqrestore(&pci_lock, flags);
 418
 419         return locked;
 420 }
 421 EXPORT_SYMBOL_GPL(pci_cfg_access_trylock);
 422
 423 /**
 424  * pci_cfg_access_unlock - Unlock PCI config reads/writes
 425  * @dev:        pci device struct
 426  *
 427  * This function allows PCI config accesses to resume.
 428  */
 429 void pci_cfg_access_unlock(struct pci_dev *dev)
 430 {
 431         unsigned long flags;
 432
 433         raw_spin_lock_irqsave(&pci_lock, flags);
 434
 435         /* This indicates a problem in the caller, but we don't need
 436          * to kill them, unlike a double-block above. */
 437         WARN_ON(!dev->block_cfg_access);
 438
 439         dev->block_cfg_access = 0;
 440         wake_up_all(&pci_cfg_wait);
 441         raw_spin_unlock_irqrestore(&pci_lock, flags);
 442 }
 443 EXPORT_SYMBOL_GPL(pci_cfg_access_unlock);
 444
 445 static inline int pcie_cap_version(const struct pci_dev *dev)
 446 {
 447         return pcie_caps_reg(dev) & PCI_EXP_FLAGS_VERS;
 448 }
 449
 450 static inline bool pcie_cap_has_lnkctl(const struct pci_dev *dev)
 451 {
 452         int type = pci_pcie_type(dev);
 453
 454         return type == PCI_EXP_TYPE_ENDPOINT ||
 455                type == PCI_EXP_TYPE_LEG_END ||
 456                type == PCI_EXP_TYPE_ROOT_PORT ||
 457                type == PCI_EXP_TYPE_UPSTREAM ||
 458                type == PCI_EXP_TYPE_DOWNSTREAM ||
 459                type == PCI_EXP_TYPE_PCI_BRIDGE ||
 460                type == PCI_EXP_TYPE_PCIE_BRIDGE;
 461 }
 462
 463 static inline bool pcie_cap_has_sltctl(const struct pci_dev *dev)
 464 {
 465         int type = pci_pcie_type(dev);
 466
 467         return (type == PCI_EXP_TYPE_ROOT_PORT ||
 468                 type == PCI_EXP_TYPE_DOWNSTREAM) &&
 469                pcie_caps_reg(dev) & PCI_EXP_FLAGS_SLOT;
 470 }
 471
 472 static inline bool pcie_cap_has_rtctl(const struct pci_dev *dev)
 473 {
 474         int type = pci_pcie_type(dev);
 475
 476         return type == PCI_EXP_TYPE_ROOT_PORT ||
 477                type == PCI_EXP_TYPE_RC_EC;
 478 }
 479
 480 static bool pcie_capability_reg_implemented(struct pci_dev *dev, int pos)
 481 {
 482         if (!pci_is_pcie(dev))
 483                 return false;
 484
 485         switch (pos) {
 486         case PCI_EXP_FLAGS:
 487                 return true;
 488         case PCI_EXP_DEVCAP:
 489         case PCI_EXP_DEVCTL:
 490         case PCI_EXP_DEVSTA:
 491                 return true;
 492         case PCI_EXP_LNKCAP:
 493         case PCI_EXP_LNKCTL:
 494         case PCI_EXP_LNKSTA:
 495                 return pcie_cap_has_lnkctl(dev);
 496         case PCI_EXP_SLTCAP:
 497         case PCI_EXP_SLTCTL:
 498         case PCI_EXP_SLTSTA:
 499                 return pcie_cap_has_sltctl(dev);
 500         case PCI_EXP_RTCTL:
 501         case PCI_EXP_RTCAP:
 502         case PCI_EXP_RTSTA:
 503                 return pcie_cap_has_rtctl(dev);
 504         case PCI_EXP_DEVCAP2:
 505         case PCI_EXP_DEVCTL2:
 506         case PCI_EXP_LNKCAP2:
 507         case PCI_EXP_LNKCTL2:
 508         case PCI_EXP_LNKSTA2:
 509                 return pcie_cap_version(dev) > 1;
 510         default:
 511                 return false;
 512         }
 513 }
 514
 515 /*
 516  * Note that these accessor functions are only for the "PCI Express
 517  * Capability" (see PCIe spec r3.0, sec 7.8).  They do not apply to the
 518  * other "PCI Express Extended Capabilities" (AER, VC, ACS, MFVC, etc.)
 519  */
 520 int pcie_capability_read_word(struct pci_dev *dev, int pos, u16 *val)
 521 {
 522         int ret;
 523
 524         *val = 0;
 525         if (pos & 1)
 526                 return -EINVAL;
 527
 528         if (pcie_capability_reg_implemented(dev, pos)) {
 529                 ret = pci_read_config_word(dev, pci_pcie_cap(dev) + pos, val);
 530                 /*
 531                  * Reset *val to 0 if pci_read_config_word() fails, it may
 532                  * have been written as 0xFFFF if hardware error happens
 533                  * during pci_read_config_word().
 534                  */
 535                 if (ret)
 536                         *val = 0;
 537                 return ret;
 538         }
 539
 540         /*
 541          * For Functions that do not implement the Slot Capabilities,
 542          * Slot Status, and Slot Control registers, these spaces must
 543          * be hardwired to 0b, with the exception of the Presence Detect
 544          * State bit in the Slot Status register of Downstream Ports,
 545          * which must be hardwired to 1b.  (PCIe Base Spec 3.0, sec 7.8)
 546          */
 547         if (pci_is_pcie(dev) && pos == PCI_EXP_SLTSTA &&
 548                  pci_pcie_type(dev) == PCI_EXP_TYPE_DOWNSTREAM) {
 549                 *val = PCI_EXP_SLTSTA_PDS;
 550         }
 551
 552         return 0;
 553 }
 554 EXPORT_SYMBOL(pcie_capability_read_word);
 555
 556 int pcie_capability_read_dword(struct pci_dev *dev, int pos, u32 *val)
 557 {
 558         int ret;
 559
 560         *val = 0;
 561         if (pos & 3)
 562                 return -EINVAL;
 563
 564         if (pcie_capability_reg_implemented(dev, pos)) {
 565                 ret = pci_read_config_dword(dev, pci_pcie_cap(dev) + pos, val);
 566                 /*
 567                  * Reset *val to 0 if pci_read_config_dword() fails, it may
 568                  * have been written as 0xFFFFFFFF if hardware error happens
 569                  * during pci_read_config_dword().
 570                  */
 571                 if (ret)
 572                         *val = 0;
 573                 return ret;
 574         }
 575
 576         if (pci_is_pcie(dev) && pos == PCI_EXP_SLTCTL &&
 577                  pci_pcie_type(dev) == PCI_EXP_TYPE_DOWNSTREAM) {
 578                 *val = PCI_EXP_SLTSTA_PDS;
 579         }
 580
 581         return 0;
 582 }
 583 EXPORT_SYMBOL(pcie_capability_read_dword);
 584
 585 int pcie_capability_write_word(struct pci_dev *dev, int pos, u16 val)
 586 {
 587         if (pos & 1)
 588                 return -EINVAL;
 589
 590         if (!pcie_capability_reg_implemented(dev, pos))
 591                 return 0;
 592
 593         return pci_write_config_word(dev, pci_pcie_cap(dev) + pos, val);
 594 }
 595 EXPORT_SYMBOL(pcie_capability_write_word);
 596
 597 int pcie_capability_write_dword(struct pci_dev *dev, int pos, u32 val)
 598 {
 599         if (pos & 3)
 600                 return -EINVAL;
 601
 602         if (!pcie_capability_reg_implemented(dev, pos))
 603                 return 0;
 604
 605         return pci_write_config_dword(dev, pci_pcie_cap(dev) + pos, val);
 606 }
 607 EXPORT_SYMBOL(pcie_capability_write_dword);
 608
 609 int pcie_capability_clear_and_set_word(struct pci_dev *dev, int pos,
 610                                        u16 clear, u16 set)
 611 {
 612         int ret;
 613         u16 val;
 614
 615         ret = pcie_capability_read_word(dev, pos, &val);
 616         if (!ret) {
 617                 val &= ~clear;
 618                 val |= set;
 619                 ret = pcie_capability_write_word(dev, pos, val);
 620         }
 621
 622         return ret;
 623 }
 624 EXPORT_SYMBOL(pcie_capability_clear_and_set_word);
 625
 626 int pcie_capability_clear_and_set_dword(struct pci_dev *dev, int pos,
 627                                         u32 clear, u32 set)
 628 {
 629         int ret;
 630         u32 val;
 631
 632         ret = pcie_capability_read_dword(dev, pos, &val);
 633         if (!ret) {
 634                 val &= ~clear;
 635                 val |= set;
 636                 ret = pcie_capability_write_dword(dev, pos, val);
 637         }
 638
 639         return ret;
 640 }
 641 EXPORT_SYMBOL(pcie_capability_clear_and_set_dword);