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      1 /*	$NetBSD: intel_gtt_subr.c,v 1.3 2021/12/19 12:37:36 riastradh Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2014 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Taylor R. Campbell.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     29  * POSSIBILITY OF SUCH DAMAGE.
     30  */
     31 
     32 /* Intel GTT stubs */
     33 
     34 #include <sys/cdefs.h>
     35 __KERNEL_RCSID(0, "$NetBSD: intel_gtt_subr.c,v 1.3 2021/12/19 12:37:36 riastradh Exp $");
     36 
     37 #include <sys/types.h>
     38 #include <sys/bus.h>
     39 #include <sys/errno.h>
     40 #include <sys/systm.h>
     41 
     42 #include <machine/vmparam.h>
     43 
     44 #include <dev/pci/pcivar.h>		/* XXX agpvar.h needs...  */
     45 #include <dev/pci/agpvar.h>
     46 #include <dev/pci/agp_i810var.h>
     47 
     48 #include <linux/pci.h>
     49 #include <linux/scatterlist.h>
     50 
     51 #include "drm/i915_drm.h"
     52 #include "drm/intel-gtt.h"
     53 
     54 static uint8_t
     55 pci_conf_read8(pci_chipset_tag_t pc, pcitag_t tag, bus_size_t reg)
     56 {
     57 	uint32_t v;
     58 
     59 	v = pci_conf_read(pc, tag, reg & ~3);
     60 
     61 	return 0xff & (v >> (8 * (reg & 3)));
     62 }
     63 
     64 static uint8_t
     65 pci_read8(pci_chipset_tag_t pc, int bus, int dev, int func, bus_size_t reg)
     66 {
     67 	pcitag_t tag = pci_make_tag(pc, bus, dev, func);
     68 
     69 	return pci_conf_read8(pc, tag, reg);
     70 }
     71 
     72 static uint16_t
     73 pci_conf_read16(pci_chipset_tag_t pc, pcitag_t tag, bus_size_t reg)
     74 {
     75 	uint32_t v;
     76 
     77 	KASSERT((reg & 1) == 0);
     78 
     79 	v = pci_conf_read(pc, tag, reg & ~2);
     80 
     81 	return 0xffff & (v >> (8 * (reg & 2)));
     82 }
     83 
     84 static uint16_t
     85 pci_read16(pci_chipset_tag_t pc, int bus, int dev, int func, bus_size_t reg)
     86 {
     87 	pcitag_t tag = pci_make_tag(pc, bus, dev, func);
     88 
     89 	return pci_conf_read16(pc, tag, reg);
     90 }
     91 
     92 /* Access to this should be single-threaded.  */
     93 static struct {
     94 	bus_dma_segment_t	scratch_seg;
     95 	bus_dmamap_t		scratch_map;
     96 } intel_gtt;
     97 
     98 /* XXX This logic should be merged with agp_i810.c.  */
     99 struct resource intel_graphics_stolen_res;
    100 
    101 static bus_size_t
    102 i830_tseg_size(pci_chipset_tag_t pc)
    103 {
    104 	uint8_t esmramc = pci_read8(pc, 0, 0, 0, I830_ESMRAMC);
    105 
    106 	if ((esmramc & TSEG_ENABLE) == 0)
    107 		return 0;
    108 
    109 	return (esmramc & I830_TSEG_SIZE_1M) ? 1024*1024 : 512*1024;
    110 }
    111 
    112 static bus_size_t
    113 i845_tseg_size(pci_chipset_tag_t pc)
    114 {
    115 	uint8_t esmramc = pci_read8(pc, 0, 0, 0, I845_ESMRAMC);
    116 
    117 	if ((esmramc & TSEG_ENABLE) == 0)
    118 		return 0;
    119 
    120 	switch (esmramc & I845_TSEG_SIZE_MASK) {
    121 	case I845_TSEG_SIZE_512K:
    122 		return 512*1024;
    123 	case I845_TSEG_SIZE_1M:
    124 		return 1024*1024;
    125 	default:
    126 		return 0;
    127 	}
    128 }
    129 
    130 static bus_size_t
    131 i85x_tseg_size(pci_chipset_tag_t pc)
    132 {
    133 	uint8_t esmramc = pci_read8(pc, 0, 0, 0, I85X_ESMRAMC);
    134 
    135 	if ((esmramc & TSEG_ENABLE) == 0)
    136 		return 0;
    137 
    138 	return 1024*1024;
    139 }
    140 
    141 static bus_size_t
    142 i830_tom(pci_chipset_tag_t pc)
    143 {
    144 	uint8_t drb3 = pci_read8(pc, 0, 0, 0, I830_DRB3);
    145 
    146 	return (bus_size_t)32*1024*1024 * drb3;
    147 }
    148 
    149 static bus_size_t
    150 i85x_tom(pci_chipset_tag_t pc)
    151 {
    152 	uint8_t drb3 = pci_read8(pc, 0, 0, 1, I85X_DRB3);
    153 
    154 	return (bus_size_t)32*1024*1024 * drb3;
    155 }
    156 
    157 static bus_size_t
    158 i830_stolen_size(pci_chipset_tag_t pc, pcitag_t tag)
    159 {
    160 	uint16_t gmch_ctrl = pci_read16(pc, 0, 0, 0, I830_GMCH_CTRL);
    161 
    162 	switch (gmch_ctrl & I830_GMCH_GMS_MASK) {
    163 	case I830_GMCH_GMS_STOLEN_512:
    164 		return 512*1024;
    165 	case I830_GMCH_GMS_STOLEN_1024:
    166 		return 1024*1024;
    167 	case I830_GMCH_GMS_STOLEN_8192:
    168 		return 8*1024*1024;
    169 	case I830_GMCH_GMS_LOCAL:
    170 	default:
    171 		aprint_error("%s: invalid gmch_ctrl 0x%04x\n", __func__,
    172 		    gmch_ctrl);
    173 		return 0;
    174 	}
    175 }
    176 
    177 static bus_size_t
    178 gen3_stolen_size(pci_chipset_tag_t pc, pcitag_t tag)
    179 {
    180 	uint16_t gmch_ctrl = pci_read16(pc, 0, 0, 0, I830_GMCH_CTRL);
    181 
    182 	switch (gmch_ctrl & I855_GMCH_GMS_MASK) {
    183 	case I855_GMCH_GMS_STOLEN_1M:
    184 		return 1024*1024;
    185 	case I855_GMCH_GMS_STOLEN_4M:
    186 		return 4*1024*1024;
    187 	case I855_GMCH_GMS_STOLEN_8M:
    188 		return 8*1024*1024;
    189 	case I855_GMCH_GMS_STOLEN_16M:
    190 		return 16*1024*1024;
    191 	case I855_GMCH_GMS_STOLEN_32M:
    192 		return 32*1024*1024;
    193 	case I915_GMCH_GMS_STOLEN_48M:
    194 		return 48*1024*1024;
    195 	case I915_GMCH_GMS_STOLEN_64M:
    196 		return 64*1024*1024;
    197 	case G33_GMCH_GMS_STOLEN_128M:
    198 		return 128*1024*1024;
    199 	case G33_GMCH_GMS_STOLEN_256M:
    200 		return 256*1024*1024;
    201 	case INTEL_GMCH_GMS_STOLEN_96M:
    202 		return 96*1024*1024;
    203 	case INTEL_GMCH_GMS_STOLEN_160M:
    204 		return 160*1024*1024;
    205 	case INTEL_GMCH_GMS_STOLEN_224M:
    206 		return 224*1024*1024;
    207 	case INTEL_GMCH_GMS_STOLEN_352M:
    208 		return 352*1024*1024;
    209 	default:
    210 		aprint_error("%s: invalid gmch_ctrl 0x%04x\n", __func__,
    211 		    gmch_ctrl);
    212 		return 0;
    213 	}
    214 }
    215 
    216 static bus_size_t
    217 gen6_stolen_size(pci_chipset_tag_t pc, pcitag_t tag)
    218 {
    219 	uint16_t gmch_ctrl = pci_conf_read16(pc, tag, SNB_GMCH_CTRL);
    220 	uint16_t gms = (gmch_ctrl >> SNB_GMCH_GMS_SHIFT) & SNB_GMCH_GMS_MASK;
    221 
    222 	return (bus_size_t)32*1024*1024 * gms;
    223 }
    224 
    225 static bus_size_t
    226 gen8_stolen_size(pci_chipset_tag_t pc, pcitag_t tag)
    227 {
    228 	uint16_t gmch_ctrl = pci_conf_read16(pc, tag, SNB_GMCH_CTRL);
    229 	uint16_t gms = (gmch_ctrl >> BDW_GMCH_GMS_SHIFT) & BDW_GMCH_GMS_MASK;
    230 
    231 	return (bus_size_t)32*1024*1024 * gms;
    232 }
    233 
    234 static bus_size_t
    235 chv_stolen_size(pci_chipset_tag_t pc, pcitag_t tag)
    236 {
    237 	uint16_t gmch_ctrl = pci_conf_read16(pc, tag, SNB_GMCH_CTRL);
    238 	uint16_t gms = (gmch_ctrl >> SNB_GMCH_GMS_SHIFT) & SNB_GMCH_GMS_MASK;
    239 
    240 	if (gms <= 0x10)
    241 		return (bus_size_t)32*1024*1024 * gms;
    242 	else if (gms <= 0x16)
    243 		return (bus_size_t)(8 + 4*(gms - 0x11))*1024*1024;
    244 	else
    245 		return (bus_size_t)(36 + 4*(gms - 0x17))*1024*1024;
    246 }
    247 
    248 static bus_size_t
    249 gen9_stolen_size(pci_chipset_tag_t pc, pcitag_t tag)
    250 {
    251 	uint16_t gmch_ctrl = pci_conf_read16(pc, tag, SNB_GMCH_CTRL);
    252 	uint16_t gms = (gmch_ctrl >> BDW_GMCH_GMS_SHIFT) & BDW_GMCH_GMS_MASK;
    253 
    254 	if (gms <= 0xef)
    255 		return (bus_size_t)32*1024*1024 * gms;
    256 	else
    257 		return (bus_size_t)(4 + 4*(gms - 0xf0))*1024*1024;
    258 }
    259 
    260 static bus_addr_t
    261 i830_stolen_base(pci_chipset_tag_t pc, pcitag_t tag, bus_size_t stolen_size)
    262 {
    263 
    264 	return i830_tom(pc) - i830_tseg_size(pc) - stolen_size;
    265 }
    266 
    267 static bus_addr_t
    268 i845_stolen_base(pci_chipset_tag_t pc, pcitag_t tag, bus_size_t stolen_size)
    269 {
    270 
    271 	return i830_tom(pc) - i845_tseg_size(pc) - stolen_size;
    272 }
    273 
    274 static bus_addr_t
    275 i85x_stolen_base(pci_chipset_tag_t pc, pcitag_t tag, bus_size_t stolen_size)
    276 {
    277 
    278 	return i85x_tom(pc) - i85x_tseg_size(pc) - stolen_size;
    279 }
    280 
    281 static bus_addr_t
    282 i865_stolen_base(pci_chipset_tag_t pc, pcitag_t tag, bus_size_t stolen_size)
    283 {
    284 	uint16_t toud = pci_read16(pc, 0, 0, 0, I865_TOUD);
    285 
    286 	return i845_tseg_size(pc) + (64*1024 * toud);
    287 }
    288 
    289 static bus_addr_t
    290 gen3_stolen_base(pci_chipset_tag_t pc, pcitag_t tag, bus_size_t stolen_size)
    291 {
    292 	uint32_t bsm = pci_conf_read(pc, tag, INTEL_BSM);
    293 
    294 	return bsm & INTEL_BSM_MASK;
    295 }
    296 
    297 static bus_addr_t
    298 gen11_stolen_base(pci_chipset_tag_t pc, pcitag_t tag, bus_size_t stolen_size)
    299 {
    300 	uint32_t bsm;
    301 
    302 	bsm = pci_conf_read(pc, tag, INTEL_GEN11_BSM_DW0) & INTEL_BSM_MASK;
    303 	bsm |= (uint64_t)pci_conf_read(pc, tag, INTEL_GEN11_BSM_DW1) << 32;
    304 
    305 	return bsm;
    306 }
    307 
    308 struct intel_stolen_ops {
    309 	bus_size_t	(*size)(pci_chipset_tag_t, pcitag_t);
    310 	bus_addr_t	(*base)(pci_chipset_tag_t, pcitag_t, bus_size_t);
    311 };
    312 
    313 static const struct intel_stolen_ops i830_stolen_ops = {
    314 	.size = i830_stolen_size,
    315 	.base = i830_stolen_base,
    316 };
    317 
    318 static const struct intel_stolen_ops i845_stolen_ops = {
    319 	.size = i830_stolen_size,
    320 	.base = i845_stolen_base,
    321 };
    322 
    323 static const struct intel_stolen_ops i85x_stolen_ops = {
    324 	.size = gen3_stolen_size,
    325 	.base = i85x_stolen_base,
    326 };
    327 
    328 static const struct intel_stolen_ops i865_stolen_ops = {
    329 	.size = gen3_stolen_size,
    330 	.base = i865_stolen_base,
    331 };
    332 
    333 static const struct intel_stolen_ops gen3_stolen_ops = {
    334 	.size = gen3_stolen_size,
    335 	.base = gen3_stolen_base,
    336 };
    337 
    338 static const struct intel_stolen_ops gen6_stolen_ops = {
    339 	.size = gen6_stolen_size,
    340 	.base = gen3_stolen_base,
    341 };
    342 
    343 static const struct intel_stolen_ops gen8_stolen_ops = {
    344 	.size = gen8_stolen_size,
    345 	.base = gen3_stolen_base,
    346 };
    347 
    348 static const struct intel_stolen_ops gen9_stolen_ops = {
    349 	.size = gen9_stolen_size,
    350 	.base = gen3_stolen_base,
    351 };
    352 
    353 static const struct intel_stolen_ops chv_stolen_ops = {
    354 	.size = chv_stolen_size,
    355 	.base = gen3_stolen_base,
    356 };
    357 
    358 static const struct intel_stolen_ops gen11_stolen_ops = {
    359 	.size = gen9_stolen_size,
    360 	.base = gen11_stolen_base,
    361 };
    362 
    363 static const struct pci_device_id intel_stolen_ids[] = {
    364 	INTEL_I830_IDS(&i830_stolen_ops),
    365 	INTEL_I845G_IDS(&i845_stolen_ops),
    366 	INTEL_I85X_IDS(&i85x_stolen_ops),
    367 	INTEL_I865G_IDS(&i865_stolen_ops),
    368 	INTEL_I915G_IDS(&gen3_stolen_ops),
    369 	INTEL_I915GM_IDS(&gen3_stolen_ops),
    370 	INTEL_I945G_IDS(&gen3_stolen_ops),
    371 	INTEL_I945GM_IDS(&gen3_stolen_ops),
    372 	INTEL_VLV_IDS(&gen6_stolen_ops),
    373 	INTEL_PINEVIEW_G_IDS(&gen3_stolen_ops),
    374 	INTEL_PINEVIEW_M_IDS(&gen3_stolen_ops),
    375 	INTEL_I965G_IDS(&gen3_stolen_ops),
    376 	INTEL_G33_IDS(&gen3_stolen_ops),
    377 	INTEL_I965GM_IDS(&gen3_stolen_ops),
    378 	INTEL_GM45_IDS(&gen3_stolen_ops),
    379 	INTEL_G45_IDS(&gen3_stolen_ops),
    380 	INTEL_IRONLAKE_D_IDS(&gen3_stolen_ops),
    381 	INTEL_IRONLAKE_M_IDS(&gen3_stolen_ops),
    382 	INTEL_SNB_D_IDS(&gen6_stolen_ops),
    383 	INTEL_SNB_M_IDS(&gen6_stolen_ops),
    384 	INTEL_IVB_M_IDS(&gen6_stolen_ops),
    385 	INTEL_IVB_D_IDS(&gen6_stolen_ops),
    386 	INTEL_HSW_IDS(&gen6_stolen_ops),
    387 	INTEL_BDW_IDS(&gen8_stolen_ops),
    388 	INTEL_CHV_IDS(&chv_stolen_ops),
    389 	INTEL_SKL_IDS(&gen9_stolen_ops),
    390 	INTEL_BXT_IDS(&gen9_stolen_ops),
    391 	INTEL_KBL_IDS(&gen9_stolen_ops),
    392 	INTEL_CFL_IDS(&gen9_stolen_ops),
    393 	INTEL_GLK_IDS(&gen9_stolen_ops),
    394 	INTEL_CNL_IDS(&gen9_stolen_ops),
    395 	INTEL_ICL_11_IDS(&gen11_stolen_ops),
    396 	INTEL_EHL_IDS(&gen11_stolen_ops),
    397 	INTEL_TGL_12_IDS(&gen11_stolen_ops),
    398 };
    399 
    400 void
    401 intel_gtt_get(uint64_t *va_size, bus_addr_t *aper_base,
    402     resource_size_t *aper_size)
    403 {
    404 	struct agp_softc *sc;
    405 	pci_chipset_tag_t pc;
    406 	pcitag_t tag;
    407 	struct agp_i810_softc *isc;
    408 	const struct intel_stolen_ops *ops;
    409 	bus_addr_t stolen_base;
    410 	bus_size_t stolen_size;
    411 	unsigned i;
    412 
    413 	if ((sc = agp_i810_sc) == NULL) {
    414 		*va_size = 0;
    415 		*aper_base = 0;
    416 		*aper_size = 0;
    417 		return;
    418 	}
    419 
    420 	pc = sc->as_pc;
    421 	tag = sc->as_tag;
    422 
    423 	isc = sc->as_chipc;
    424 	*va_size = ((size_t)(isc->gtt_size/sizeof(uint32_t)) << PAGE_SHIFT);
    425 	*aper_base = sc->as_apaddr;
    426 	*aper_size = sc->as_apsize;
    427 
    428 	for (i = 0; i < __arraycount(intel_stolen_ids); i++) {
    429 		if (intel_stolen_ids[i].device == PCI_PRODUCT(sc->as_id)) {
    430 			ops = (const struct intel_stolen_ops *)
    431 			    intel_stolen_ids[i].driver_data;
    432 			stolen_size = (*ops->size)(pc, tag);
    433 			stolen_base = (*ops->base)(pc, tag, stolen_size);
    434 			intel_graphics_stolen_res.start = stolen_base;
    435 			intel_graphics_stolen_res.end =
    436 			    stolen_base + stolen_size - 1;
    437 			break;
    438 		}
    439 	}
    440 }
    441 
    442 int
    443 intel_gmch_probe(struct pci_dev *bridge_pci __unused,
    444     struct pci_dev *gpu __unused, struct agp_bridge_data *bridge_agp __unused)
    445 {
    446 	struct agp_softc *const sc = agp_i810_sc;
    447 	int nsegs;
    448 	int error;
    449 
    450 	if (sc == NULL)
    451 		return 0;
    452 
    453 	error = bus_dmamem_alloc(sc->as_dmat, PAGE_SIZE, PAGE_SIZE, 0,
    454 	    &intel_gtt.scratch_seg, 1, &nsegs, BUS_DMA_WAITOK);
    455 	if (error)
    456 		goto fail0;
    457 	KASSERT(nsegs == 1);
    458 
    459 	error = bus_dmamap_create(sc->as_dmat, PAGE_SIZE, 1, PAGE_SIZE, 0,
    460 	    BUS_DMA_WAITOK, &intel_gtt.scratch_map);
    461 	if (error)
    462 		goto fail1;
    463 
    464 	error = bus_dmamap_load_raw(sc->as_dmat, intel_gtt.scratch_map,
    465 	    &intel_gtt.scratch_seg, 1, PAGE_SIZE, BUS_DMA_WAITOK);
    466 	if (error)
    467 		goto fail2;
    468 
    469 	/* Success!  */
    470 	return 1;
    471 
    472 fail3: __unused
    473 	bus_dmamap_unload(sc->as_dmat, intel_gtt.scratch_map);
    474 fail2:	bus_dmamap_destroy(sc->as_dmat, intel_gtt.scratch_map);
    475 fail1:	bus_dmamem_free(sc->as_dmat, &intel_gtt.scratch_seg, 1);
    476 fail0:	KASSERT(error);
    477 	return 0;
    478 }
    479 
    480 void
    481 intel_gmch_remove(void)
    482 {
    483 	struct agp_softc *const sc = agp_i810_sc;
    484 
    485 	bus_dmamap_unload(sc->as_dmat, intel_gtt.scratch_map);
    486 	bus_dmamap_destroy(sc->as_dmat, intel_gtt.scratch_map);
    487 	bus_dmamem_free(sc->as_dmat, &intel_gtt.scratch_seg, 1);
    488 }
    489 
    490 bool
    491 intel_enable_gtt(void)
    492 {
    493 	struct agp_softc *sc = agp_i810_sc;
    494 	struct agp_i810_softc *isc;
    495 
    496 	if (sc == NULL)
    497 		return false;
    498 	isc = sc->as_chipc;
    499 	agp_i810_reset(isc);
    500 	return true;
    501 }
    502 
    503 void
    504 intel_gtt_chipset_flush(void)
    505 {
    506 
    507 	KASSERT(agp_i810_sc != NULL);
    508 	agp_i810_chipset_flush(agp_i810_sc->as_chipc);
    509 }
    510 
    511 static int
    512 intel_gtt_flags(unsigned flags)
    513 {
    514 	int gtt_flags = AGP_I810_GTT_VALID;
    515 
    516 	switch (flags) {
    517 	case AGP_USER_MEMORY:
    518 		break;
    519 	case AGP_USER_CACHED_MEMORY:
    520 		gtt_flags |= AGP_I810_GTT_CACHED;
    521 		break;
    522 	default:
    523 		panic("invalid intel gtt flags: %x", flags);
    524 	}
    525 
    526 	return gtt_flags;
    527 }
    528 
    529 void
    530 intel_gtt_insert_page(bus_addr_t addr, unsigned va_page, unsigned flags)
    531 {
    532 	struct agp_i810_softc *const isc = agp_i810_sc->as_chipc;
    533 	off_t va = (off_t)va_page << PAGE_SHIFT;
    534 	int gtt_flags = intel_gtt_flags(flags);
    535 	int error;
    536 
    537 	error = agp_i810_write_gtt_entry(isc, va, addr, gtt_flags);
    538 	if (error)
    539 		device_printf(agp_i810_sc->as_dev,
    540 		    "write gtt entry"
    541 		    " %"PRIxMAX" -> %"PRIxMAX" (flags=%x) failed: %d\n",
    542 		    (uintmax_t)va, (uintmax_t)addr, flags,
    543 		    error);
    544 	agp_i810_post_gtt_entry(isc, va);
    545 	intel_gtt_chipset_flush();
    546 }
    547 
    548 void
    549 intel_gtt_insert_sg_entries(struct sg_table *sg, unsigned va_page,
    550     unsigned flags)
    551 {
    552 	bus_dmamap_t dmamap = sg->sgl[0].sg_dmamap;
    553 	struct agp_i810_softc *const isc = agp_i810_sc->as_chipc;
    554 	off_t va = (off_t)va_page << PAGE_SHIFT;
    555 	unsigned seg;
    556 	int gtt_flags = intel_gtt_flags(flags);
    557 	int error;
    558 
    559 	KASSERT(0 <= va);
    560 	KASSERT((va >> PAGE_SHIFT) == va_page);
    561 	KASSERT(0 < dmamap->dm_nsegs);
    562 
    563 	for (seg = 0; seg < dmamap->dm_nsegs; seg++) {
    564 		const bus_addr_t addr = dmamap->dm_segs[seg].ds_addr;
    565 		bus_size_t len;
    566 
    567 		for (len = dmamap->dm_segs[seg].ds_len;
    568 		     len >= PAGE_SIZE;
    569 		     len -= PAGE_SIZE, va += PAGE_SIZE) {
    570 			error = agp_i810_write_gtt_entry(isc, va, addr,
    571 			    gtt_flags);
    572 			if (error)
    573 				device_printf(agp_i810_sc->as_dev,
    574 				    "write gtt entry"
    575 				    " %"PRIxMAX" -> %"PRIxMAX" (flags=%x)"
    576 				    " failed: %d\n",
    577 				    (uintmax_t)va, (uintmax_t)addr, flags,
    578 				    error);
    579 		}
    580 		KASSERTMSG(len == 0,
    581 		    "segment length not divisible by PAGE_SIZE: %jx",
    582 		    (uintmax_t)dmamap->dm_segs[seg].ds_len);
    583 	}
    584 	agp_i810_post_gtt_entry(isc, (va - PAGE_SIZE));
    585 	intel_gtt_chipset_flush();
    586 }
    587 
    588 void
    589 intel_gtt_clear_range(unsigned va_page, unsigned npages)
    590 {
    591 	struct agp_i810_softc *const isc = agp_i810_sc->as_chipc;
    592 	const bus_addr_t addr = intel_gtt.scratch_map->dm_segs[0].ds_addr;
    593 	const int gtt_flags = AGP_I810_GTT_VALID;
    594 	off_t va = (va_page << PAGE_SHIFT);
    595 
    596 	KASSERT(0 <= va);
    597 	KASSERT((va >> PAGE_SHIFT) == va_page);
    598 	KASSERT(0 < npages);
    599 
    600 	while (npages--) {
    601 		agp_i810_write_gtt_entry(isc, va, addr, gtt_flags);
    602 		va += PAGE_SIZE;
    603 	}
    604 	agp_i810_post_gtt_entry(isc, va - PAGE_SIZE);
    605 }
    606