xref: /src/sys/i386/pci/pci_cfgreg.c (revision c0020399a650364d0134f79f3fa319f84064372d)
1 /*-
2  * Copyright (c) 1997, Stefan Esser <se@freebsd.org>
3  * Copyright (c) 2000, Michael Smith <msmith@freebsd.org>
4  * Copyright (c) 2000, BSDi
5  * Copyright (c) 2004, Scott Long <scottl@freebsd.org>
6  * All rights reserved.
7  *
8  * Redistribution and use in source and binary forms, with or without
9  * modification, are permitted provided that the following conditions
10  * are met:
11  * 1. Redistributions of source code must retain the above copyright
12  *    notice unmodified, this list of conditions, and the following
13  *    disclaimer.
14  * 2. Redistributions in binary form must reproduce the above copyright
15  *    notice, this list of conditions and the following disclaimer in the
16  *    documentation and/or other materials provided with the distribution.
17  *
18  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
19  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
20  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
21  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
22  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
23  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
24  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
25  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
26  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
27  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28  */
29 
30 #include <sys/cdefs.h>
31 __FBSDID("$FreeBSD$");
32 
33 #include "opt_xbox.h"
34 
35 #include <sys/param.h>
36 #include <sys/systm.h>
37 #include <sys/bus.h>
38 #include <sys/lock.h>
39 #include <sys/kernel.h>
40 #include <sys/mutex.h>
41 #include <sys/malloc.h>
42 #include <sys/queue.h>
43 #include <dev/pci/pcivar.h>
44 #include <dev/pci/pcireg.h>
45 #include <machine/pci_cfgreg.h>
46 #include <machine/pc/bios.h>
47 
48 #include <vm/vm.h>
49 #include <vm/vm_param.h>
50 #include <vm/vm_kern.h>
51 #include <vm/vm_extern.h>
52 #include <vm/pmap.h>
53 #include <machine/pmap.h>
54 
55 #ifdef XBOX
56 #include <machine/xbox.h>
57 #endif
58 
59 #define PRVERB(a) do {							\
60 	if (bootverbose)						\
61 		printf a ;						\
62 } while(0)
63 
64 #define PCIE_CACHE 8
65 struct pcie_cfg_elem {
66 	TAILQ_ENTRY(pcie_cfg_elem)	elem;
67 	vm_offset_t	vapage;
68 	vm_paddr_t	papage;
69 };
70 
71 enum {
72 	CFGMECH_NONE = 0,
73 	CFGMECH_1,
74 	CFGMECH_2,
75 	CFGMECH_PCIE,
76 };
77 
78 static TAILQ_HEAD(pcie_cfg_list, pcie_cfg_elem) pcie_list[MAXCPU];
79 static uint64_t pcie_base;
80 static int pcie_minbus, pcie_maxbus;
81 static uint32_t pcie_badslots;
82 static int cfgmech;
83 static int devmax;
84 static struct mtx pcicfg_mtx;
85 static int mcfg_enable = 1;
86 TUNABLE_INT("hw.pci.mcfg", &mcfg_enable);
87 
88 static uint32_t	pci_docfgregread(int bus, int slot, int func, int reg,
89 		    int bytes);
90 static int	pcireg_cfgread(int bus, int slot, int func, int reg, int bytes);
91 static void	pcireg_cfgwrite(int bus, int slot, int func, int reg, int data, int bytes);
92 #ifndef XEN
93 static int	pcireg_cfgopen(void);
94 #endif
95 static int	pciereg_cfgread(int bus, unsigned slot, unsigned func,
96 		    unsigned reg, unsigned bytes);
97 static void	pciereg_cfgwrite(int bus, unsigned slot, unsigned func,
98 		    unsigned reg, int data, unsigned bytes);
99 
100 /*
101  * Some BIOS writers seem to want to ignore the spec and put
102  * 0 in the intline rather than 255 to indicate none.  Some use
103  * numbers in the range 128-254 to indicate something strange and
104  * apparently undocumented anywhere.  Assume these are completely bogus
105  * and map them to 255, which means "none".
106  */
107 static __inline int
108 pci_i386_map_intline(int line)
109 {
110 	if (line == 0 || line >= 128)
111 		return (PCI_INVALID_IRQ);
112 	return (line);
113 }
114 
115 #ifndef XEN
116 static u_int16_t
117 pcibios_get_version(void)
118 {
119 	struct bios_regs args;
120 
121 	if (PCIbios.ventry == 0) {
122 		PRVERB(("pcibios: No call entry point\n"));
123 		return (0);
124 	}
125 	args.eax = PCIBIOS_BIOS_PRESENT;
126 	if (bios32(&args, PCIbios.ventry, GSEL(GCODE_SEL, SEL_KPL))) {
127 		PRVERB(("pcibios: BIOS_PRESENT call failed\n"));
128 		return (0);
129 	}
130 	if (args.edx != 0x20494350) {
131 		PRVERB(("pcibios: BIOS_PRESENT didn't return 'PCI ' in edx\n"));
132 		return (0);
133 	}
134 	return (args.ebx & 0xffff);
135 }
136 #endif
137 
138 /*
139  * Initialise access to PCI configuration space
140  */
141 int
142 pci_cfgregopen(void)
143 {
144 #ifdef XEN
145 	return (0);
146 #else
147 	static int		opened = 0;
148 	uint64_t		pciebar;
149 	u_int16_t		vid, did;
150 	u_int16_t		v;
151 
152 	if (opened)
153 		return (1);
154 
155 	if (cfgmech == CFGMECH_NONE && pcireg_cfgopen() == 0)
156 		return (0);
157 
158 	v = pcibios_get_version();
159 	if (v > 0)
160 		PRVERB(("pcibios: BIOS version %x.%02x\n", (v & 0xff00) >> 8,
161 		    v & 0xff));
162 	mtx_init(&pcicfg_mtx, "pcicfg", NULL, MTX_SPIN);
163 	opened = 1;
164 
165 	/* $PIR requires PCI BIOS 2.10 or greater. */
166 	if (v >= 0x0210)
167 		pci_pir_open();
168 
169 	if (cfgmech == CFGMECH_PCIE)
170 		return (1);
171 
172 	/*
173 	 * Grope around in the PCI config space to see if this is a
174 	 * chipset that is capable of doing memory-mapped config cycles.
175 	 * This also implies that it can do PCIe extended config cycles.
176 	 */
177 
178 	/* Check for supported chipsets */
179 	vid = pci_cfgregread(0, 0, 0, PCIR_VENDOR, 2);
180 	did = pci_cfgregread(0, 0, 0, PCIR_DEVICE, 2);
181 	switch (vid) {
182 	case 0x8086:
183 		switch (did) {
184 		case 0x3590:
185 		case 0x3592:
186 			/* Intel 7520 or 7320 */
187 			pciebar = pci_cfgregread(0, 0, 0, 0xce, 2) << 16;
188 			pcie_cfgregopen(pciebar, 0, 255);
189 			break;
190 		case 0x2580:
191 		case 0x2584:
192 		case 0x2590:
193 			/* Intel 915, 925, or 915GM */
194 			pciebar = pci_cfgregread(0, 0, 0, 0x48, 4);
195 			pcie_cfgregopen(pciebar, 0, 255);
196 			break;
197 		}
198 	}
199 
200 	return(1);
201 #endif
202 }
203 
204 static uint32_t
205 pci_docfgregread(int bus, int slot, int func, int reg, int bytes)
206 {
207 
208 	if (cfgmech == CFGMECH_PCIE &&
209 	    (bus >= pcie_minbus && bus <= pcie_maxbus) &&
210 	    (bus != 0 || !(1 << slot & pcie_badslots)))
211 		return (pciereg_cfgread(bus, slot, func, reg, bytes));
212 	else
213 		return (pcireg_cfgread(bus, slot, func, reg, bytes));
214 }
215 
216 /*
217  * Read configuration space register
218  */
219 u_int32_t
220 pci_cfgregread(int bus, int slot, int func, int reg, int bytes)
221 {
222 	uint32_t line;
223 
224 	/*
225 	 * Some BIOS writers seem to want to ignore the spec and put
226 	 * 0 in the intline rather than 255 to indicate none.  The rest of
227 	 * the code uses 255 as an invalid IRQ.
228 	 */
229 	if (reg == PCIR_INTLINE && bytes == 1) {
230 		line = pci_docfgregread(bus, slot, func, PCIR_INTLINE, 1);
231 		return (pci_i386_map_intline(line));
232 	}
233 	return (pci_docfgregread(bus, slot, func, reg, bytes));
234 }
235 
236 /*
237  * Write configuration space register
238  */
239 void
240 pci_cfgregwrite(int bus, int slot, int func, int reg, u_int32_t data, int bytes)
241 {
242 
243 	if (cfgmech == CFGMECH_PCIE &&
244 	    (bus >= pcie_minbus && bus <= pcie_maxbus) &&
245 	    (bus != 0 || !(1 << slot & pcie_badslots)))
246 		pciereg_cfgwrite(bus, slot, func, reg, data, bytes);
247 	else
248 		pcireg_cfgwrite(bus, slot, func, reg, data, bytes);
249 }
250 
251 /*
252  * Configuration space access using direct register operations
253  */
254 
255 /* enable configuration space accesses and return data port address */
256 static int
257 pci_cfgenable(unsigned bus, unsigned slot, unsigned func, int reg, int bytes)
258 {
259 	int dataport = 0;
260 
261 #ifdef XBOX
262 	if (arch_i386_is_xbox) {
263 		/*
264 		 * The Xbox MCPX chipset is a derivative of the nForce 1
265 		 * chipset. It almost has the same bus layout; some devices
266 		 * cannot be used, because they have been removed.
267 		 */
268 
269 		/*
270 		 * Devices 00:00.1 and 00:00.2 used to be memory controllers on
271 		 * the nForce chipset, but on the Xbox, using them will lockup
272 		 * the chipset.
273 		 */
274 		if (bus == 0 && slot == 0 && (func == 1 || func == 2))
275 			return dataport;
276 
277 		/*
278 		 * Bus 1 only contains a VGA controller at 01:00.0. When you try
279 		 * to probe beyond that device, you only get garbage, which
280 		 * could cause lockups.
281 		 */
282 		if (bus == 1 && (slot != 0 || func != 0))
283 			return dataport;
284 
285 		/*
286 		 * Bus 2 used to contain the AGP controller, but the Xbox MCPX
287 		 * doesn't have one. Probing it can cause lockups.
288 		 */
289 		if (bus >= 2)
290 			return dataport;
291 	}
292 #endif
293 
294 	if (bus <= PCI_BUSMAX
295 	    && slot < devmax
296 	    && func <= PCI_FUNCMAX
297 	    && reg <= PCI_REGMAX
298 	    && bytes != 3
299 	    && (unsigned) bytes <= 4
300 	    && (reg & (bytes - 1)) == 0) {
301 		switch (cfgmech) {
302 		case CFGMECH_PCIE:
303 		case CFGMECH_1:
304 			outl(CONF1_ADDR_PORT, (1 << 31)
305 			    | (bus << 16) | (slot << 11)
306 			    | (func << 8) | (reg & ~0x03));
307 			dataport = CONF1_DATA_PORT + (reg & 0x03);
308 			break;
309 		case CFGMECH_2:
310 			outb(CONF2_ENABLE_PORT, 0xf0 | (func << 1));
311 			outb(CONF2_FORWARD_PORT, bus);
312 			dataport = 0xc000 | (slot << 8) | reg;
313 			break;
314 		}
315 	}
316 	return (dataport);
317 }
318 
319 /* disable configuration space accesses */
320 static void
321 pci_cfgdisable(void)
322 {
323 	switch (cfgmech) {
324 	case CFGMECH_PCIE:
325 	case CFGMECH_1:
326 		/*
327 		 * Do nothing for the config mechanism 1 case.
328 		 * Writing a 0 to the address port can apparently
329 		 * confuse some bridges and cause spurious
330 		 * access failures.
331 		 */
332 		break;
333 	case CFGMECH_2:
334 		outb(CONF2_ENABLE_PORT, 0);
335 		break;
336 	}
337 }
338 
339 static int
340 pcireg_cfgread(int bus, int slot, int func, int reg, int bytes)
341 {
342 	int data = -1;
343 	int port;
344 
345 	mtx_lock_spin(&pcicfg_mtx);
346 	port = pci_cfgenable(bus, slot, func, reg, bytes);
347 	if (port != 0) {
348 		switch (bytes) {
349 		case 1:
350 			data = inb(port);
351 			break;
352 		case 2:
353 			data = inw(port);
354 			break;
355 		case 4:
356 			data = inl(port);
357 			break;
358 		}
359 		pci_cfgdisable();
360 	}
361 	mtx_unlock_spin(&pcicfg_mtx);
362 	return (data);
363 }
364 
365 static void
366 pcireg_cfgwrite(int bus, int slot, int func, int reg, int data, int bytes)
367 {
368 	int port;
369 
370 	mtx_lock_spin(&pcicfg_mtx);
371 	port = pci_cfgenable(bus, slot, func, reg, bytes);
372 	if (port != 0) {
373 		switch (bytes) {
374 		case 1:
375 			outb(port, data);
376 			break;
377 		case 2:
378 			outw(port, data);
379 			break;
380 		case 4:
381 			outl(port, data);
382 			break;
383 		}
384 		pci_cfgdisable();
385 	}
386 	mtx_unlock_spin(&pcicfg_mtx);
387 }
388 
389 #ifndef XEN
390 /* check whether the configuration mechanism has been correctly identified */
391 static int
392 pci_cfgcheck(int maxdev)
393 {
394 	uint32_t id, class;
395 	uint8_t header;
396 	uint8_t device;
397 	int port;
398 
399 	if (bootverbose)
400 		printf("pci_cfgcheck:\tdevice ");
401 
402 	for (device = 0; device < maxdev; device++) {
403 		if (bootverbose)
404 			printf("%d ", device);
405 
406 		port = pci_cfgenable(0, device, 0, 0, 4);
407 		id = inl(port);
408 		if (id == 0 || id == 0xffffffff)
409 			continue;
410 
411 		port = pci_cfgenable(0, device, 0, 8, 4);
412 		class = inl(port) >> 8;
413 		if (bootverbose)
414 			printf("[class=%06x] ", class);
415 		if (class == 0 || (class & 0xf870ff) != 0)
416 			continue;
417 
418 		port = pci_cfgenable(0, device, 0, 14, 1);
419 		header = inb(port);
420 		if (bootverbose)
421 			printf("[hdr=%02x] ", header);
422 		if ((header & 0x7e) != 0)
423 			continue;
424 
425 		if (bootverbose)
426 			printf("is there (id=%08x)\n", id);
427 
428 		pci_cfgdisable();
429 		return (1);
430 	}
431 	if (bootverbose)
432 		printf("-- nothing found\n");
433 
434 	pci_cfgdisable();
435 	return (0);
436 }
437 
438 static int
439 pcireg_cfgopen(void)
440 {
441 	uint32_t mode1res, oldval1;
442 	uint8_t mode2res, oldval2;
443 
444 	/* Check for type #1 first. */
445 	oldval1 = inl(CONF1_ADDR_PORT);
446 
447 	if (bootverbose) {
448 		printf("pci_open(1):\tmode 1 addr port (0x0cf8) is 0x%08x\n",
449 		    oldval1);
450 	}
451 
452 	cfgmech = CFGMECH_1;
453 	devmax = 32;
454 
455 	outl(CONF1_ADDR_PORT, CONF1_ENABLE_CHK);
456 	DELAY(1);
457 	mode1res = inl(CONF1_ADDR_PORT);
458 	outl(CONF1_ADDR_PORT, oldval1);
459 
460 	if (bootverbose)
461 		printf("pci_open(1a):\tmode1res=0x%08x (0x%08lx)\n",  mode1res,
462 		    CONF1_ENABLE_CHK);
463 
464 	if (mode1res) {
465 		if (pci_cfgcheck(32))
466 			return (cfgmech);
467 	}
468 
469 	outl(CONF1_ADDR_PORT, CONF1_ENABLE_CHK1);
470 	mode1res = inl(CONF1_ADDR_PORT);
471 	outl(CONF1_ADDR_PORT, oldval1);
472 
473 	if (bootverbose)
474 		printf("pci_open(1b):\tmode1res=0x%08x (0x%08lx)\n",  mode1res,
475 		    CONF1_ENABLE_CHK1);
476 
477 	if ((mode1res & CONF1_ENABLE_MSK1) == CONF1_ENABLE_RES1) {
478 		if (pci_cfgcheck(32))
479 			return (cfgmech);
480 	}
481 
482 	/* Type #1 didn't work, so try type #2. */
483 	oldval2 = inb(CONF2_ENABLE_PORT);
484 
485 	if (bootverbose) {
486 		printf("pci_open(2):\tmode 2 enable port (0x0cf8) is 0x%02x\n",
487 		    oldval2);
488 	}
489 
490 	if ((oldval2 & 0xf0) == 0) {
491 
492 		cfgmech = CFGMECH_2;
493 		devmax = 16;
494 
495 		outb(CONF2_ENABLE_PORT, CONF2_ENABLE_CHK);
496 		mode2res = inb(CONF2_ENABLE_PORT);
497 		outb(CONF2_ENABLE_PORT, oldval2);
498 
499 		if (bootverbose)
500 			printf("pci_open(2a):\tmode2res=0x%02x (0x%02x)\n",
501 			    mode2res, CONF2_ENABLE_CHK);
502 
503 		if (mode2res == CONF2_ENABLE_RES) {
504 			if (bootverbose)
505 				printf("pci_open(2a):\tnow trying mechanism 2\n");
506 
507 			if (pci_cfgcheck(16))
508 				return (cfgmech);
509 		}
510 	}
511 
512 	/* Nothing worked, so punt. */
513 	cfgmech = CFGMECH_NONE;
514 	devmax = 0;
515 	return (cfgmech);
516 }
517 
518 int
519 pcie_cfgregopen(uint64_t base, uint8_t minbus, uint8_t maxbus)
520 {
521 	struct pcie_cfg_list *pcielist;
522 	struct pcie_cfg_elem *pcie_array, *elem;
523 #ifdef SMP
524 	struct pcpu *pc;
525 #endif
526 	vm_offset_t va;
527 	uint32_t val1, val2;
528 	int i, slot;
529 
530 	if (!mcfg_enable)
531 		return (0);
532 
533 	if (minbus != 0)
534 		return (0);
535 
536 #ifndef PAE
537 	if (base >= 0x100000000) {
538 		if (bootverbose)
539 			printf(
540 	    "PCI: Memory Mapped PCI configuration area base 0x%jx too high\n",
541 			    (uintmax_t)base);
542 		return (0);
543 	}
544 #endif
545 
546 	if (bootverbose)
547 		printf("PCIe: Memory Mapped configuration base @ 0x%jx\n",
548 		    (uintmax_t)base);
549 
550 #ifdef SMP
551 	SLIST_FOREACH(pc, &cpuhead, pc_allcpu)
552 #endif
553 	{
554 
555 		pcie_array = malloc(sizeof(struct pcie_cfg_elem) * PCIE_CACHE,
556 		    M_DEVBUF, M_NOWAIT);
557 		if (pcie_array == NULL)
558 			return (0);
559 
560 		va = kmem_alloc_nofault(kernel_map, PCIE_CACHE * PAGE_SIZE);
561 		if (va == 0) {
562 			free(pcie_array, M_DEVBUF);
563 			return (0);
564 		}
565 
566 #ifdef SMP
567 		pcielist = &pcie_list[pc->pc_cpuid];
568 #else
569 		pcielist = &pcie_list[0];
570 #endif
571 		TAILQ_INIT(pcielist);
572 		for (i = 0; i < PCIE_CACHE; i++) {
573 			elem = &pcie_array[i];
574 			elem->vapage = va + (i * PAGE_SIZE);
575 			elem->papage = 0;
576 			TAILQ_INSERT_HEAD(pcielist, elem, elem);
577 		}
578 	}
579 
580 	pcie_base = base;
581 	pcie_minbus = minbus;
582 	pcie_maxbus = maxbus;
583 	cfgmech = CFGMECH_PCIE;
584 	devmax = 32;
585 
586 	/*
587 	 * On some AMD systems, some of the devices on bus 0 are
588 	 * inaccessible using memory-mapped PCI config access.  Walk
589 	 * bus 0 looking for such devices.  For these devices, we will
590 	 * fall back to using type 1 config access instead.
591 	 */
592 	if (pci_cfgregopen() != 0) {
593 		for (slot = 0; slot < 32; slot++) {
594 			val1 = pcireg_cfgread(0, slot, 0, 0, 4);
595 			if (val1 == 0xffffffff)
596 				continue;
597 
598 			val2 = pciereg_cfgread(0, slot, 0, 0, 4);
599 			if (val2 != val1)
600 				pcie_badslots |= (1 << slot);
601 		}
602 	}
603 
604 	return (1);
605 }
606 #endif /* !XEN */
607 
608 #define PCIE_PADDR(bar, reg, bus, slot, func)	\
609 	((bar)				|	\
610 	(((bus) & 0xff) << 20)		|	\
611 	(((slot) & 0x1f) << 15)		|	\
612 	(((func) & 0x7) << 12)		|	\
613 	((reg) & 0xfff))
614 
615 /*
616  * Find an element in the cache that matches the physical page desired, or
617  * create a new mapping from the least recently used element.
618  * A very simple LRU algorithm is used here, does it need to be more
619  * efficient?
620  */
621 static __inline struct pcie_cfg_elem *
622 pciereg_findelem(vm_paddr_t papage)
623 {
624 	struct pcie_cfg_list *pcielist;
625 	struct pcie_cfg_elem *elem;
626 
627 	pcielist = &pcie_list[PCPU_GET(cpuid)];
628 	TAILQ_FOREACH(elem, pcielist, elem) {
629 		if (elem->papage == papage)
630 			break;
631 	}
632 
633 	if (elem == NULL) {
634 		elem = TAILQ_LAST(pcielist, pcie_cfg_list);
635 		if (elem->papage != 0) {
636 			pmap_kremove(elem->vapage);
637 			invlpg(elem->vapage);
638 		}
639 		pmap_kenter(elem->vapage, papage);
640 		elem->papage = papage;
641 	}
642 
643 	if (elem != TAILQ_FIRST(pcielist)) {
644 		TAILQ_REMOVE(pcielist, elem, elem);
645 		TAILQ_INSERT_HEAD(pcielist, elem, elem);
646 	}
647 	return (elem);
648 }
649 
650 static int
651 pciereg_cfgread(int bus, unsigned slot, unsigned func, unsigned reg,
652     unsigned bytes)
653 {
654 	struct pcie_cfg_elem *elem;
655 	volatile vm_offset_t va;
656 	vm_paddr_t pa, papage;
657 	int data = -1;
658 
659 	if (bus < pcie_minbus || bus > pcie_maxbus || slot >= 32 ||
660 	    func > PCI_FUNCMAX || reg >= 0x1000 || bytes > 4 || bytes == 3)
661 		return (-1);
662 
663 	critical_enter();
664 	pa = PCIE_PADDR(pcie_base, reg, bus, slot, func);
665 	papage = pa & ~PAGE_MASK;
666 	elem = pciereg_findelem(papage);
667 	va = elem->vapage | (pa & PAGE_MASK);
668 
669 	switch (bytes) {
670 	case 4:
671 		data = *(volatile uint32_t *)(va);
672 		break;
673 	case 2:
674 		data = *(volatile uint16_t *)(va);
675 		break;
676 	case 1:
677 		data = *(volatile uint8_t *)(va);
678 		break;
679 	}
680 
681 	critical_exit();
682 	return (data);
683 }
684 
685 static void
686 pciereg_cfgwrite(int bus, unsigned slot, unsigned func, unsigned reg, int data,
687     unsigned bytes)
688 {
689 	struct pcie_cfg_elem *elem;
690 	volatile vm_offset_t va;
691 	vm_paddr_t pa, papage;
692 
693 	if (bus < pcie_minbus || bus > pcie_maxbus || slot >= 32 ||
694 	    func > PCI_FUNCMAX || reg >= 0x1000)
695 		return;
696 
697 	critical_enter();
698 	pa = PCIE_PADDR(pcie_base, reg, bus, slot, func);
699 	papage = pa & ~PAGE_MASK;
700 	elem = pciereg_findelem(papage);
701 	va = elem->vapage | (pa & PAGE_MASK);
702 
703 	switch (bytes) {
704 	case 4:
705 		*(volatile uint32_t *)(va) = data;
706 		break;
707 	case 2:
708 		*(volatile uint16_t *)(va) = data;
709 		break;
710 	case 1:
711 		*(volatile uint8_t *)(va) = data;
712 		break;
713 	}
714 
715 	critical_exit();
716 }
717