xref: /openbmc/linux/drivers/pci/access.c (revision 4f3db074)
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 int pci_generic_config_read(struct pci_bus *bus, unsigned int devfn,
71 			    int where, int size, u32 *val)
72 {
73 	void __iomem *addr;
74 
75 	addr = bus->ops->map_bus(bus, devfn, where);
76 	if (!addr) {
77 		*val = ~0;
78 		return PCIBIOS_DEVICE_NOT_FOUND;
79 	}
80 
81 	if (size == 1)
82 		*val = readb(addr);
83 	else if (size == 2)
84 		*val = readw(addr);
85 	else
86 		*val = readl(addr);
87 
88 	return PCIBIOS_SUCCESSFUL;
89 }
90 EXPORT_SYMBOL_GPL(pci_generic_config_read);
91 
92 int pci_generic_config_write(struct pci_bus *bus, unsigned int devfn,
93 			     int where, int size, u32 val)
94 {
95 	void __iomem *addr;
96 
97 	addr = bus->ops->map_bus(bus, devfn, where);
98 	if (!addr)
99 		return PCIBIOS_DEVICE_NOT_FOUND;
100 
101 	if (size == 1)
102 		writeb(val, addr);
103 	else if (size == 2)
104 		writew(val, addr);
105 	else
106 		writel(val, addr);
107 
108 	return PCIBIOS_SUCCESSFUL;
109 }
110 EXPORT_SYMBOL_GPL(pci_generic_config_write);
111 
112 int pci_generic_config_read32(struct pci_bus *bus, unsigned int devfn,
113 			      int where, int size, u32 *val)
114 {
115 	void __iomem *addr;
116 
117 	addr = bus->ops->map_bus(bus, devfn, where & ~0x3);
118 	if (!addr) {
119 		*val = ~0;
120 		return PCIBIOS_DEVICE_NOT_FOUND;
121 	}
122 
123 	*val = readl(addr);
124 
125 	if (size <= 2)
126 		*val = (*val >> (8 * (where & 3))) & ((1 << (size * 8)) - 1);
127 
128 	return PCIBIOS_SUCCESSFUL;
129 }
130 EXPORT_SYMBOL_GPL(pci_generic_config_read32);
131 
132 int pci_generic_config_write32(struct pci_bus *bus, unsigned int devfn,
133 			       int where, int size, u32 val)
134 {
135 	void __iomem *addr;
136 	u32 mask, tmp;
137 
138 	addr = bus->ops->map_bus(bus, devfn, where & ~0x3);
139 	if (!addr)
140 		return PCIBIOS_DEVICE_NOT_FOUND;
141 
142 	if (size == 4) {
143 		writel(val, addr);
144 		return PCIBIOS_SUCCESSFUL;
145 	} else {
146 		mask = ~(((1 << (size * 8)) - 1) << ((where & 0x3) * 8));
147 	}
148 
149 	tmp = readl(addr) & mask;
150 	tmp |= val << ((where & 0x3) * 8);
151 	writel(tmp, addr);
152 
153 	return PCIBIOS_SUCCESSFUL;
154 }
155 EXPORT_SYMBOL_GPL(pci_generic_config_write32);
156 
157 /**
158  * pci_bus_set_ops - Set raw operations of pci bus
159  * @bus:	pci bus struct
160  * @ops:	new raw operations
161  *
162  * Return previous raw operations
163  */
164 struct pci_ops *pci_bus_set_ops(struct pci_bus *bus, struct pci_ops *ops)
165 {
166 	struct pci_ops *old_ops;
167 	unsigned long flags;
168 
169 	raw_spin_lock_irqsave(&pci_lock, flags);
170 	old_ops = bus->ops;
171 	bus->ops = ops;
172 	raw_spin_unlock_irqrestore(&pci_lock, flags);
173 	return old_ops;
174 }
175 EXPORT_SYMBOL(pci_bus_set_ops);
176 
177 /**
178  * pci_read_vpd - Read one entry from Vital Product Data
179  * @dev:	pci device struct
180  * @pos:	offset in vpd space
181  * @count:	number of bytes to read
182  * @buf:	pointer to where to store result
183  *
184  */
185 ssize_t pci_read_vpd(struct pci_dev *dev, loff_t pos, size_t count, void *buf)
186 {
187 	if (!dev->vpd || !dev->vpd->ops)
188 		return -ENODEV;
189 	return dev->vpd->ops->read(dev, pos, count, buf);
190 }
191 EXPORT_SYMBOL(pci_read_vpd);
192 
193 /**
194  * pci_write_vpd - Write entry to Vital Product Data
195  * @dev:	pci device struct
196  * @pos:	offset in vpd space
197  * @count:	number of bytes to write
198  * @buf:	buffer containing write data
199  *
200  */
201 ssize_t pci_write_vpd(struct pci_dev *dev, loff_t pos, size_t count, const void *buf)
202 {
203 	if (!dev->vpd || !dev->vpd->ops)
204 		return -ENODEV;
205 	return dev->vpd->ops->write(dev, pos, count, buf);
206 }
207 EXPORT_SYMBOL(pci_write_vpd);
208 
209 /*
210  * The following routines are to prevent the user from accessing PCI config
211  * space when it's unsafe to do so.  Some devices require this during BIST and
212  * we're required to prevent it during D-state transitions.
213  *
214  * We have a bit per device to indicate it's blocked and a global wait queue
215  * for callers to sleep on until devices are unblocked.
216  */
217 static DECLARE_WAIT_QUEUE_HEAD(pci_cfg_wait);
218 
219 static noinline void pci_wait_cfg(struct pci_dev *dev)
220 {
221 	DECLARE_WAITQUEUE(wait, current);
222 
223 	__add_wait_queue(&pci_cfg_wait, &wait);
224 	do {
225 		set_current_state(TASK_UNINTERRUPTIBLE);
226 		raw_spin_unlock_irq(&pci_lock);
227 		schedule();
228 		raw_spin_lock_irq(&pci_lock);
229 	} while (dev->block_cfg_access);
230 	__remove_wait_queue(&pci_cfg_wait, &wait);
231 }
232 
233 /* Returns 0 on success, negative values indicate error. */
234 #define PCI_USER_READ_CONFIG(size,type)					\
235 int pci_user_read_config_##size						\
236 	(struct pci_dev *dev, int pos, type *val)			\
237 {									\
238 	int ret = PCIBIOS_SUCCESSFUL;					\
239 	u32 data = -1;							\
240 	if (PCI_##size##_BAD)						\
241 		return -EINVAL;						\
242 	raw_spin_lock_irq(&pci_lock);				\
243 	if (unlikely(dev->block_cfg_access))				\
244 		pci_wait_cfg(dev);					\
245 	ret = dev->bus->ops->read(dev->bus, dev->devfn,			\
246 					pos, sizeof(type), &data);	\
247 	raw_spin_unlock_irq(&pci_lock);				\
248 	*val = (type)data;						\
249 	return pcibios_err_to_errno(ret);				\
250 }									\
251 EXPORT_SYMBOL_GPL(pci_user_read_config_##size);
252 
253 /* Returns 0 on success, negative values indicate error. */
254 #define PCI_USER_WRITE_CONFIG(size,type)				\
255 int pci_user_write_config_##size					\
256 	(struct pci_dev *dev, int pos, type val)			\
257 {									\
258 	int ret = PCIBIOS_SUCCESSFUL;					\
259 	if (PCI_##size##_BAD)						\
260 		return -EINVAL;						\
261 	raw_spin_lock_irq(&pci_lock);				\
262 	if (unlikely(dev->block_cfg_access))				\
263 		pci_wait_cfg(dev);					\
264 	ret = dev->bus->ops->write(dev->bus, dev->devfn,		\
265 					pos, sizeof(type), val);	\
266 	raw_spin_unlock_irq(&pci_lock);				\
267 	return pcibios_err_to_errno(ret);				\
268 }									\
269 EXPORT_SYMBOL_GPL(pci_user_write_config_##size);
270 
271 PCI_USER_READ_CONFIG(byte, u8)
272 PCI_USER_READ_CONFIG(word, u16)
273 PCI_USER_READ_CONFIG(dword, u32)
274 PCI_USER_WRITE_CONFIG(byte, u8)
275 PCI_USER_WRITE_CONFIG(word, u16)
276 PCI_USER_WRITE_CONFIG(dword, u32)
277 
278 /* VPD access through PCI 2.2+ VPD capability */
279 
280 #define PCI_VPD_PCI22_SIZE (PCI_VPD_ADDR_MASK + 1)
281 
282 struct pci_vpd_pci22 {
283 	struct pci_vpd base;
284 	struct mutex lock;
285 	u16	flag;
286 	bool	busy;
287 	u8	cap;
288 };
289 
290 /*
291  * Wait for last operation to complete.
292  * This code has to spin since there is no other notification from the PCI
293  * hardware. Since the VPD is often implemented by serial attachment to an
294  * EEPROM, it may take many milliseconds to complete.
295  *
296  * Returns 0 on success, negative values indicate error.
297  */
298 static int pci_vpd_pci22_wait(struct pci_dev *dev)
299 {
300 	struct pci_vpd_pci22 *vpd =
301 		container_of(dev->vpd, struct pci_vpd_pci22, base);
302 	unsigned long timeout = jiffies + HZ/20 + 2;
303 	u16 status;
304 	int ret;
305 
306 	if (!vpd->busy)
307 		return 0;
308 
309 	for (;;) {
310 		ret = pci_user_read_config_word(dev, vpd->cap + PCI_VPD_ADDR,
311 						&status);
312 		if (ret < 0)
313 			return ret;
314 
315 		if ((status & PCI_VPD_ADDR_F) == vpd->flag) {
316 			vpd->busy = false;
317 			return 0;
318 		}
319 
320 		if (time_after(jiffies, timeout)) {
321 			dev_printk(KERN_DEBUG, &dev->dev, "vpd r/w failed.  This is likely a firmware bug on this device.  Contact the card vendor for a firmware update\n");
322 			return -ETIMEDOUT;
323 		}
324 		if (fatal_signal_pending(current))
325 			return -EINTR;
326 		if (!cond_resched())
327 			udelay(10);
328 	}
329 }
330 
331 static ssize_t pci_vpd_pci22_read(struct pci_dev *dev, loff_t pos, size_t count,
332 				  void *arg)
333 {
334 	struct pci_vpd_pci22 *vpd =
335 		container_of(dev->vpd, struct pci_vpd_pci22, base);
336 	int ret;
337 	loff_t end = pos + count;
338 	u8 *buf = arg;
339 
340 	if (pos < 0 || pos > vpd->base.len || end > vpd->base.len)
341 		return -EINVAL;
342 
343 	if (mutex_lock_killable(&vpd->lock))
344 		return -EINTR;
345 
346 	ret = pci_vpd_pci22_wait(dev);
347 	if (ret < 0)
348 		goto out;
349 
350 	while (pos < end) {
351 		u32 val;
352 		unsigned int i, skip;
353 
354 		ret = pci_user_write_config_word(dev, vpd->cap + PCI_VPD_ADDR,
355 						 pos & ~3);
356 		if (ret < 0)
357 			break;
358 		vpd->busy = true;
359 		vpd->flag = PCI_VPD_ADDR_F;
360 		ret = pci_vpd_pci22_wait(dev);
361 		if (ret < 0)
362 			break;
363 
364 		ret = pci_user_read_config_dword(dev, vpd->cap + PCI_VPD_DATA, &val);
365 		if (ret < 0)
366 			break;
367 
368 		skip = pos & 3;
369 		for (i = 0;  i < sizeof(u32); i++) {
370 			if (i >= skip) {
371 				*buf++ = val;
372 				if (++pos == end)
373 					break;
374 			}
375 			val >>= 8;
376 		}
377 	}
378 out:
379 	mutex_unlock(&vpd->lock);
380 	return ret ? ret : count;
381 }
382 
383 static ssize_t pci_vpd_pci22_write(struct pci_dev *dev, loff_t pos, size_t count,
384 				   const void *arg)
385 {
386 	struct pci_vpd_pci22 *vpd =
387 		container_of(dev->vpd, struct pci_vpd_pci22, base);
388 	const u8 *buf = arg;
389 	loff_t end = pos + count;
390 	int ret = 0;
391 
392 	if (pos < 0 || (pos & 3) || (count & 3) || end > vpd->base.len)
393 		return -EINVAL;
394 
395 	if (mutex_lock_killable(&vpd->lock))
396 		return -EINTR;
397 
398 	ret = pci_vpd_pci22_wait(dev);
399 	if (ret < 0)
400 		goto out;
401 
402 	while (pos < end) {
403 		u32 val;
404 
405 		val = *buf++;
406 		val |= *buf++ << 8;
407 		val |= *buf++ << 16;
408 		val |= *buf++ << 24;
409 
410 		ret = pci_user_write_config_dword(dev, vpd->cap + PCI_VPD_DATA, val);
411 		if (ret < 0)
412 			break;
413 		ret = pci_user_write_config_word(dev, vpd->cap + PCI_VPD_ADDR,
414 						 pos | PCI_VPD_ADDR_F);
415 		if (ret < 0)
416 			break;
417 
418 		vpd->busy = true;
419 		vpd->flag = 0;
420 		ret = pci_vpd_pci22_wait(dev);
421 		if (ret < 0)
422 			break;
423 
424 		pos += sizeof(u32);
425 	}
426 out:
427 	mutex_unlock(&vpd->lock);
428 	return ret ? ret : count;
429 }
430 
431 static void pci_vpd_pci22_release(struct pci_dev *dev)
432 {
433 	kfree(container_of(dev->vpd, struct pci_vpd_pci22, base));
434 }
435 
436 static const struct pci_vpd_ops pci_vpd_pci22_ops = {
437 	.read = pci_vpd_pci22_read,
438 	.write = pci_vpd_pci22_write,
439 	.release = pci_vpd_pci22_release,
440 };
441 
442 int pci_vpd_pci22_init(struct pci_dev *dev)
443 {
444 	struct pci_vpd_pci22 *vpd;
445 	u8 cap;
446 
447 	cap = pci_find_capability(dev, PCI_CAP_ID_VPD);
448 	if (!cap)
449 		return -ENODEV;
450 	vpd = kzalloc(sizeof(*vpd), GFP_ATOMIC);
451 	if (!vpd)
452 		return -ENOMEM;
453 
454 	vpd->base.len = PCI_VPD_PCI22_SIZE;
455 	vpd->base.ops = &pci_vpd_pci22_ops;
456 	mutex_init(&vpd->lock);
457 	vpd->cap = cap;
458 	vpd->busy = false;
459 	dev->vpd = &vpd->base;
460 	return 0;
461 }
462 
463 /**
464  * pci_cfg_access_lock - Lock PCI config reads/writes
465  * @dev:	pci device struct
466  *
467  * When access is locked, any userspace reads or writes to config
468  * space and concurrent lock requests will sleep until access is
469  * allowed via pci_cfg_access_unlocked again.
470  */
471 void pci_cfg_access_lock(struct pci_dev *dev)
472 {
473 	might_sleep();
474 
475 	raw_spin_lock_irq(&pci_lock);
476 	if (dev->block_cfg_access)
477 		pci_wait_cfg(dev);
478 	dev->block_cfg_access = 1;
479 	raw_spin_unlock_irq(&pci_lock);
480 }
481 EXPORT_SYMBOL_GPL(pci_cfg_access_lock);
482 
483 /**
484  * pci_cfg_access_trylock - try to lock PCI config reads/writes
485  * @dev:	pci device struct
486  *
487  * Same as pci_cfg_access_lock, but will return 0 if access is
488  * already locked, 1 otherwise. This function can be used from
489  * atomic contexts.
490  */
491 bool pci_cfg_access_trylock(struct pci_dev *dev)
492 {
493 	unsigned long flags;
494 	bool locked = true;
495 
496 	raw_spin_lock_irqsave(&pci_lock, flags);
497 	if (dev->block_cfg_access)
498 		locked = false;
499 	else
500 		dev->block_cfg_access = 1;
501 	raw_spin_unlock_irqrestore(&pci_lock, flags);
502 
503 	return locked;
504 }
505 EXPORT_SYMBOL_GPL(pci_cfg_access_trylock);
506 
507 /**
508  * pci_cfg_access_unlock - Unlock PCI config reads/writes
509  * @dev:	pci device struct
510  *
511  * This function allows PCI config accesses to resume.
512  */
513 void pci_cfg_access_unlock(struct pci_dev *dev)
514 {
515 	unsigned long flags;
516 
517 	raw_spin_lock_irqsave(&pci_lock, flags);
518 
519 	/* This indicates a problem in the caller, but we don't need
520 	 * to kill them, unlike a double-block above. */
521 	WARN_ON(!dev->block_cfg_access);
522 
523 	dev->block_cfg_access = 0;
524 	wake_up_all(&pci_cfg_wait);
525 	raw_spin_unlock_irqrestore(&pci_lock, flags);
526 }
527 EXPORT_SYMBOL_GPL(pci_cfg_access_unlock);
528 
529 static inline int pcie_cap_version(const struct pci_dev *dev)
530 {
531 	return pcie_caps_reg(dev) & PCI_EXP_FLAGS_VERS;
532 }
533 
534 bool pcie_cap_has_lnkctl(const struct pci_dev *dev)
535 {
536 	int type = pci_pcie_type(dev);
537 
538 	return type == PCI_EXP_TYPE_ENDPOINT ||
539 	       type == PCI_EXP_TYPE_LEG_END ||
540 	       type == PCI_EXP_TYPE_ROOT_PORT ||
541 	       type == PCI_EXP_TYPE_UPSTREAM ||
542 	       type == PCI_EXP_TYPE_DOWNSTREAM ||
543 	       type == PCI_EXP_TYPE_PCI_BRIDGE ||
544 	       type == PCI_EXP_TYPE_PCIE_BRIDGE;
545 }
546 
547 static inline bool pcie_cap_has_sltctl(const struct pci_dev *dev)
548 {
549 	int type = pci_pcie_type(dev);
550 
551 	return (type == PCI_EXP_TYPE_ROOT_PORT ||
552 		type == PCI_EXP_TYPE_DOWNSTREAM) &&
553 	       pcie_caps_reg(dev) & PCI_EXP_FLAGS_SLOT;
554 }
555 
556 static inline bool pcie_cap_has_rtctl(const struct pci_dev *dev)
557 {
558 	int type = pci_pcie_type(dev);
559 
560 	return type == PCI_EXP_TYPE_ROOT_PORT ||
561 	       type == PCI_EXP_TYPE_RC_EC;
562 }
563 
564 static bool pcie_capability_reg_implemented(struct pci_dev *dev, int pos)
565 {
566 	if (!pci_is_pcie(dev))
567 		return false;
568 
569 	switch (pos) {
570 	case PCI_EXP_FLAGS:
571 		return true;
572 	case PCI_EXP_DEVCAP:
573 	case PCI_EXP_DEVCTL:
574 	case PCI_EXP_DEVSTA:
575 		return true;
576 	case PCI_EXP_LNKCAP:
577 	case PCI_EXP_LNKCTL:
578 	case PCI_EXP_LNKSTA:
579 		return pcie_cap_has_lnkctl(dev);
580 	case PCI_EXP_SLTCAP:
581 	case PCI_EXP_SLTCTL:
582 	case PCI_EXP_SLTSTA:
583 		return pcie_cap_has_sltctl(dev);
584 	case PCI_EXP_RTCTL:
585 	case PCI_EXP_RTCAP:
586 	case PCI_EXP_RTSTA:
587 		return pcie_cap_has_rtctl(dev);
588 	case PCI_EXP_DEVCAP2:
589 	case PCI_EXP_DEVCTL2:
590 	case PCI_EXP_LNKCAP2:
591 	case PCI_EXP_LNKCTL2:
592 	case PCI_EXP_LNKSTA2:
593 		return pcie_cap_version(dev) > 1;
594 	default:
595 		return false;
596 	}
597 }
598 
599 /*
600  * Note that these accessor functions are only for the "PCI Express
601  * Capability" (see PCIe spec r3.0, sec 7.8).  They do not apply to the
602  * other "PCI Express Extended Capabilities" (AER, VC, ACS, MFVC, etc.)
603  */
604 int pcie_capability_read_word(struct pci_dev *dev, int pos, u16 *val)
605 {
606 	int ret;
607 
608 	*val = 0;
609 	if (pos & 1)
610 		return -EINVAL;
611 
612 	if (pcie_capability_reg_implemented(dev, pos)) {
613 		ret = pci_read_config_word(dev, pci_pcie_cap(dev) + pos, val);
614 		/*
615 		 * Reset *val to 0 if pci_read_config_word() fails, it may
616 		 * have been written as 0xFFFF if hardware error happens
617 		 * during pci_read_config_word().
618 		 */
619 		if (ret)
620 			*val = 0;
621 		return ret;
622 	}
623 
624 	/*
625 	 * For Functions that do not implement the Slot Capabilities,
626 	 * Slot Status, and Slot Control registers, these spaces must
627 	 * be hardwired to 0b, with the exception of the Presence Detect
628 	 * State bit in the Slot Status register of Downstream Ports,
629 	 * which must be hardwired to 1b.  (PCIe Base Spec 3.0, sec 7.8)
630 	 */
631 	if (pci_is_pcie(dev) && pos == PCI_EXP_SLTSTA &&
632 		 pci_pcie_type(dev) == PCI_EXP_TYPE_DOWNSTREAM) {
633 		*val = PCI_EXP_SLTSTA_PDS;
634 	}
635 
636 	return 0;
637 }
638 EXPORT_SYMBOL(pcie_capability_read_word);
639 
640 int pcie_capability_read_dword(struct pci_dev *dev, int pos, u32 *val)
641 {
642 	int ret;
643 
644 	*val = 0;
645 	if (pos & 3)
646 		return -EINVAL;
647 
648 	if (pcie_capability_reg_implemented(dev, pos)) {
649 		ret = pci_read_config_dword(dev, pci_pcie_cap(dev) + pos, val);
650 		/*
651 		 * Reset *val to 0 if pci_read_config_dword() fails, it may
652 		 * have been written as 0xFFFFFFFF if hardware error happens
653 		 * during pci_read_config_dword().
654 		 */
655 		if (ret)
656 			*val = 0;
657 		return ret;
658 	}
659 
660 	if (pci_is_pcie(dev) && pos == PCI_EXP_SLTCTL &&
661 		 pci_pcie_type(dev) == PCI_EXP_TYPE_DOWNSTREAM) {
662 		*val = PCI_EXP_SLTSTA_PDS;
663 	}
664 
665 	return 0;
666 }
667 EXPORT_SYMBOL(pcie_capability_read_dword);
668 
669 int pcie_capability_write_word(struct pci_dev *dev, int pos, u16 val)
670 {
671 	if (pos & 1)
672 		return -EINVAL;
673 
674 	if (!pcie_capability_reg_implemented(dev, pos))
675 		return 0;
676 
677 	return pci_write_config_word(dev, pci_pcie_cap(dev) + pos, val);
678 }
679 EXPORT_SYMBOL(pcie_capability_write_word);
680 
681 int pcie_capability_write_dword(struct pci_dev *dev, int pos, u32 val)
682 {
683 	if (pos & 3)
684 		return -EINVAL;
685 
686 	if (!pcie_capability_reg_implemented(dev, pos))
687 		return 0;
688 
689 	return pci_write_config_dword(dev, pci_pcie_cap(dev) + pos, val);
690 }
691 EXPORT_SYMBOL(pcie_capability_write_dword);
692 
693 int pcie_capability_clear_and_set_word(struct pci_dev *dev, int pos,
694 				       u16 clear, u16 set)
695 {
696 	int ret;
697 	u16 val;
698 
699 	ret = pcie_capability_read_word(dev, pos, &val);
700 	if (!ret) {
701 		val &= ~clear;
702 		val |= set;
703 		ret = pcie_capability_write_word(dev, pos, val);
704 	}
705 
706 	return ret;
707 }
708 EXPORT_SYMBOL(pcie_capability_clear_and_set_word);
709 
710 int pcie_capability_clear_and_set_dword(struct pci_dev *dev, int pos,
711 					u32 clear, u32 set)
712 {
713 	int ret;
714 	u32 val;
715 
716 	ret = pcie_capability_read_dword(dev, pos, &val);
717 	if (!ret) {
718 		val &= ~clear;
719 		val |= set;
720 		ret = pcie_capability_write_dword(dev, pos, val);
721 	}
722 
723 	return ret;
724 }
725 EXPORT_SYMBOL(pcie_capability_clear_and_set_dword);
726