xref: /openbmc/linux/drivers/gpu/drm/i915/gt/intel_gtt.h (revision 32c2e6dd)
1 /* SPDX-License-Identifier: MIT */
2 /*
3  * Copyright © 2020 Intel Corporation
4  *
5  * Please try to maintain the following order within this file unless it makes
6  * sense to do otherwise. From top to bottom:
7  * 1. typedefs
8  * 2. #defines, and macros
9  * 3. structure definitions
10  * 4. function prototypes
11  *
12  * Within each section, please try to order by generation in ascending order,
13  * from top to bottom (ie. gen6 on the top, gen8 on the bottom).
14  */
15 
16 #ifndef __INTEL_GTT_H__
17 #define __INTEL_GTT_H__
18 
19 #include <linux/io-mapping.h>
20 #include <linux/kref.h>
21 #include <linux/mm.h>
22 #include <linux/pagevec.h>
23 #include <linux/scatterlist.h>
24 #include <linux/workqueue.h>
25 
26 #include <drm/drm_mm.h>
27 
28 #include "gt/intel_reset.h"
29 #include "i915_selftest.h"
30 #include "i915_vma_types.h"
31 
32 #define I915_GFP_ALLOW_FAIL (GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_NOWARN)
33 
34 #if IS_ENABLED(CONFIG_DRM_I915_TRACE_GTT)
35 #define DBG(...) trace_printk(__VA_ARGS__)
36 #else
37 #define DBG(...)
38 #endif
39 
40 #define NALLOC 3 /* 1 normal, 1 for concurrent threads, 1 for preallocation */
41 
42 #define I915_GTT_PAGE_SIZE_4K	BIT_ULL(12)
43 #define I915_GTT_PAGE_SIZE_64K	BIT_ULL(16)
44 #define I915_GTT_PAGE_SIZE_2M	BIT_ULL(21)
45 
46 #define I915_GTT_PAGE_SIZE I915_GTT_PAGE_SIZE_4K
47 #define I915_GTT_MAX_PAGE_SIZE I915_GTT_PAGE_SIZE_2M
48 
49 #define I915_GTT_PAGE_MASK -I915_GTT_PAGE_SIZE
50 
51 #define I915_GTT_MIN_ALIGNMENT I915_GTT_PAGE_SIZE
52 
53 #define I915_FENCE_REG_NONE -1
54 #define I915_MAX_NUM_FENCES 32
55 /* 32 fences + sign bit for FENCE_REG_NONE */
56 #define I915_MAX_NUM_FENCE_BITS 6
57 
58 typedef u32 gen6_pte_t;
59 typedef u64 gen8_pte_t;
60 
61 #define ggtt_total_entries(ggtt) ((ggtt)->vm.total >> PAGE_SHIFT)
62 
63 #define I915_PTES(pte_len)		((unsigned int)(PAGE_SIZE / (pte_len)))
64 #define I915_PTE_MASK(pte_len)		(I915_PTES(pte_len) - 1)
65 #define I915_PDES			512
66 #define I915_PDE_MASK			(I915_PDES - 1)
67 
68 /* gen6-hsw has bit 11-4 for physical addr bit 39-32 */
69 #define GEN6_GTT_ADDR_ENCODE(addr)	((addr) | (((addr) >> 28) & 0xff0))
70 #define GEN6_PTE_ADDR_ENCODE(addr)	GEN6_GTT_ADDR_ENCODE(addr)
71 #define GEN6_PDE_ADDR_ENCODE(addr)	GEN6_GTT_ADDR_ENCODE(addr)
72 #define GEN6_PTE_CACHE_LLC		(2 << 1)
73 #define GEN6_PTE_UNCACHED		(1 << 1)
74 #define GEN6_PTE_VALID			REG_BIT(0)
75 
76 #define GEN6_PTES			I915_PTES(sizeof(gen6_pte_t))
77 #define GEN6_PD_SIZE		        (I915_PDES * PAGE_SIZE)
78 #define GEN6_PD_ALIGN			(PAGE_SIZE * 16)
79 #define GEN6_PDE_SHIFT			22
80 #define GEN6_PDE_VALID			REG_BIT(0)
81 #define NUM_PTE(pde_shift)     (1 << (pde_shift - PAGE_SHIFT))
82 
83 #define GEN7_PTE_CACHE_L3_LLC		(3 << 1)
84 
85 #define BYT_PTE_SNOOPED_BY_CPU_CACHES	REG_BIT(2)
86 #define BYT_PTE_WRITEABLE		REG_BIT(1)
87 
88 /*
89  * Cacheability Control is a 4-bit value. The low three bits are stored in bits
90  * 3:1 of the PTE, while the fourth bit is stored in bit 11 of the PTE.
91  */
92 #define HSW_CACHEABILITY_CONTROL(bits)	((((bits) & 0x7) << 1) | \
93 					 (((bits) & 0x8) << (11 - 3)))
94 #define HSW_WB_LLC_AGE3			HSW_CACHEABILITY_CONTROL(0x2)
95 #define HSW_WB_LLC_AGE0			HSW_CACHEABILITY_CONTROL(0x3)
96 #define HSW_WB_ELLC_LLC_AGE3		HSW_CACHEABILITY_CONTROL(0x8)
97 #define HSW_WB_ELLC_LLC_AGE0		HSW_CACHEABILITY_CONTROL(0xb)
98 #define HSW_WT_ELLC_LLC_AGE3		HSW_CACHEABILITY_CONTROL(0x7)
99 #define HSW_WT_ELLC_LLC_AGE0		HSW_CACHEABILITY_CONTROL(0x6)
100 #define HSW_PTE_UNCACHED		(0)
101 #define HSW_GTT_ADDR_ENCODE(addr)	((addr) | (((addr) >> 28) & 0x7f0))
102 #define HSW_PTE_ADDR_ENCODE(addr)	HSW_GTT_ADDR_ENCODE(addr)
103 
104 /*
105  * GEN8 32b style address is defined as a 3 level page table:
106  * 31:30 | 29:21 | 20:12 |  11:0
107  * PDPE  |  PDE  |  PTE  | offset
108  * The difference as compared to normal x86 3 level page table is the PDPEs are
109  * programmed via register.
110  *
111  * GEN8 48b style address is defined as a 4 level page table:
112  * 47:39 | 38:30 | 29:21 | 20:12 |  11:0
113  * PML4E | PDPE  |  PDE  |  PTE  | offset
114  */
115 #define GEN8_3LVL_PDPES			4
116 
117 #define PPAT_UNCACHED			(_PAGE_PWT | _PAGE_PCD)
118 #define PPAT_CACHED_PDE			0 /* WB LLC */
119 #define PPAT_CACHED			_PAGE_PAT /* WB LLCeLLC */
120 #define PPAT_DISPLAY_ELLC		_PAGE_PCD /* WT eLLC */
121 
122 #define CHV_PPAT_SNOOP			REG_BIT(6)
123 #define GEN8_PPAT_AGE(x)		((x)<<4)
124 #define GEN8_PPAT_LLCeLLC		(3<<2)
125 #define GEN8_PPAT_LLCELLC		(2<<2)
126 #define GEN8_PPAT_LLC			(1<<2)
127 #define GEN8_PPAT_WB			(3<<0)
128 #define GEN8_PPAT_WT			(2<<0)
129 #define GEN8_PPAT_WC			(1<<0)
130 #define GEN8_PPAT_UC			(0<<0)
131 #define GEN8_PPAT_ELLC_OVERRIDE		(0<<2)
132 #define GEN8_PPAT(i, x)			((u64)(x) << ((i) * 8))
133 
134 #define GEN8_PDE_IPS_64K BIT(11)
135 #define GEN8_PDE_PS_2M   BIT(7)
136 
137 enum i915_cache_level;
138 
139 struct drm_i915_file_private;
140 struct drm_i915_gem_object;
141 struct i915_fence_reg;
142 struct i915_vma;
143 struct intel_gt;
144 
145 #define for_each_sgt_daddr(__dp, __iter, __sgt) \
146 	__for_each_sgt_daddr(__dp, __iter, __sgt, I915_GTT_PAGE_SIZE)
147 
148 struct i915_page_table {
149 	struct drm_i915_gem_object *base;
150 	union {
151 		atomic_t used;
152 		struct i915_page_table *stash;
153 	};
154 };
155 
156 struct i915_page_directory {
157 	struct i915_page_table pt;
158 	spinlock_t lock;
159 	void **entry;
160 };
161 
162 #define __px_choose_expr(x, type, expr, other) \
163 	__builtin_choose_expr( \
164 	__builtin_types_compatible_p(typeof(x), type) || \
165 	__builtin_types_compatible_p(typeof(x), const type), \
166 	({ type __x = (type)(x); expr; }), \
167 	other)
168 
169 #define px_base(px) \
170 	__px_choose_expr(px, struct drm_i915_gem_object *, __x, \
171 	__px_choose_expr(px, struct i915_page_table *, __x->base, \
172 	__px_choose_expr(px, struct i915_page_directory *, __x->pt.base, \
173 	(void)0)))
174 
175 struct page *__px_page(struct drm_i915_gem_object *p);
176 dma_addr_t __px_dma(struct drm_i915_gem_object *p);
177 #define px_dma(px) (__px_dma(px_base(px)))
178 
179 #define px_pt(px) \
180 	__px_choose_expr(px, struct i915_page_table *, __x, \
181 	__px_choose_expr(px, struct i915_page_directory *, &__x->pt, \
182 	(void)0))
183 #define px_used(px) (&px_pt(px)->used)
184 
185 struct i915_vm_pt_stash {
186 	/* preallocated chains of page tables/directories */
187 	struct i915_page_table *pt[2];
188 };
189 
190 struct i915_vma_ops {
191 	/* Map an object into an address space with the given cache flags. */
192 	void (*bind_vma)(struct i915_address_space *vm,
193 			 struct i915_vm_pt_stash *stash,
194 			 struct i915_vma *vma,
195 			 enum i915_cache_level cache_level,
196 			 u32 flags);
197 	/*
198 	 * Unmap an object from an address space. This usually consists of
199 	 * setting the valid PTE entries to a reserved scratch page.
200 	 */
201 	void (*unbind_vma)(struct i915_address_space *vm,
202 			   struct i915_vma *vma);
203 
204 	int (*set_pages)(struct i915_vma *vma);
205 	void (*clear_pages)(struct i915_vma *vma);
206 };
207 
208 struct i915_address_space {
209 	struct kref ref;
210 	struct rcu_work rcu;
211 
212 	struct drm_mm mm;
213 	struct intel_gt *gt;
214 	struct drm_i915_private *i915;
215 	struct device *dma;
216 	/*
217 	 * Every address space belongs to a struct file - except for the global
218 	 * GTT that is owned by the driver (and so @file is set to NULL). In
219 	 * principle, no information should leak from one context to another
220 	 * (or between files/processes etc) unless explicitly shared by the
221 	 * owner. Tracking the owner is important in order to free up per-file
222 	 * objects along with the file, to aide resource tracking, and to
223 	 * assign blame.
224 	 */
225 	struct drm_i915_file_private *file;
226 	u64 total;		/* size addr space maps (ex. 2GB for ggtt) */
227 	u64 reserved;		/* size addr space reserved */
228 
229 	unsigned int bind_async_flags;
230 
231 	/*
232 	 * Each active user context has its own address space (in full-ppgtt).
233 	 * Since the vm may be shared between multiple contexts, we count how
234 	 * many contexts keep us "open". Once open hits zero, we are closed
235 	 * and do not allow any new attachments, and proceed to shutdown our
236 	 * vma and page directories.
237 	 */
238 	atomic_t open;
239 
240 	struct mutex mutex; /* protects vma and our lists */
241 #define VM_CLASS_GGTT 0
242 #define VM_CLASS_PPGTT 1
243 
244 	struct drm_i915_gem_object *scratch[4];
245 	/**
246 	 * List of vma currently bound.
247 	 */
248 	struct list_head bound_list;
249 
250 	/* Global GTT */
251 	bool is_ggtt:1;
252 
253 	/* Some systems support read-only mappings for GGTT and/or PPGTT */
254 	bool has_read_only:1;
255 
256 	u8 top;
257 	u8 pd_shift;
258 	u8 scratch_order;
259 
260 	struct drm_i915_gem_object *
261 		(*alloc_pt_dma)(struct i915_address_space *vm, int sz);
262 
263 	u64 (*pte_encode)(dma_addr_t addr,
264 			  enum i915_cache_level level,
265 			  u32 flags); /* Create a valid PTE */
266 #define PTE_READ_ONLY	BIT(0)
267 
268 	void (*allocate_va_range)(struct i915_address_space *vm,
269 				  struct i915_vm_pt_stash *stash,
270 				  u64 start, u64 length);
271 	void (*clear_range)(struct i915_address_space *vm,
272 			    u64 start, u64 length);
273 	void (*insert_page)(struct i915_address_space *vm,
274 			    dma_addr_t addr,
275 			    u64 offset,
276 			    enum i915_cache_level cache_level,
277 			    u32 flags);
278 	void (*insert_entries)(struct i915_address_space *vm,
279 			       struct i915_vma *vma,
280 			       enum i915_cache_level cache_level,
281 			       u32 flags);
282 	void (*cleanup)(struct i915_address_space *vm);
283 
284 	struct i915_vma_ops vma_ops;
285 
286 	I915_SELFTEST_DECLARE(struct fault_attr fault_attr);
287 	I915_SELFTEST_DECLARE(bool scrub_64K);
288 };
289 
290 /*
291  * The Graphics Translation Table is the way in which GEN hardware translates a
292  * Graphics Virtual Address into a Physical Address. In addition to the normal
293  * collateral associated with any va->pa translations GEN hardware also has a
294  * portion of the GTT which can be mapped by the CPU and remain both coherent
295  * and correct (in cases like swizzling). That region is referred to as GMADR in
296  * the spec.
297  */
298 struct i915_ggtt {
299 	struct i915_address_space vm;
300 
301 	struct io_mapping iomap;	/* Mapping to our CPU mappable region */
302 	struct resource gmadr;          /* GMADR resource */
303 	resource_size_t mappable_end;	/* End offset that we can CPU map */
304 
305 	/** "Graphics Stolen Memory" holds the global PTEs */
306 	void __iomem *gsm;
307 	void (*invalidate)(struct i915_ggtt *ggtt);
308 
309 	/** PPGTT used for aliasing the PPGTT with the GTT */
310 	struct i915_ppgtt *alias;
311 
312 	bool do_idle_maps;
313 
314 	int mtrr;
315 
316 	/** Bit 6 swizzling required for X tiling */
317 	u32 bit_6_swizzle_x;
318 	/** Bit 6 swizzling required for Y tiling */
319 	u32 bit_6_swizzle_y;
320 
321 	u32 pin_bias;
322 
323 	unsigned int num_fences;
324 	struct i915_fence_reg *fence_regs;
325 	struct list_head fence_list;
326 
327 	/**
328 	 * List of all objects in gtt_space, currently mmaped by userspace.
329 	 * All objects within this list must also be on bound_list.
330 	 */
331 	struct list_head userfault_list;
332 
333 	/* Manual runtime pm autosuspend delay for user GGTT mmaps */
334 	struct intel_wakeref_auto userfault_wakeref;
335 
336 	struct mutex error_mutex;
337 	struct drm_mm_node error_capture;
338 	struct drm_mm_node uc_fw;
339 };
340 
341 struct i915_ppgtt {
342 	struct i915_address_space vm;
343 
344 	struct i915_page_directory *pd;
345 };
346 
347 #define i915_is_ggtt(vm) ((vm)->is_ggtt)
348 
349 static inline bool
350 i915_vm_is_4lvl(const struct i915_address_space *vm)
351 {
352 	return (vm->total - 1) >> 32;
353 }
354 
355 static inline bool
356 i915_vm_has_scratch_64K(struct i915_address_space *vm)
357 {
358 	return vm->scratch_order == get_order(I915_GTT_PAGE_SIZE_64K);
359 }
360 
361 static inline bool
362 i915_vm_has_cache_coloring(struct i915_address_space *vm)
363 {
364 	return i915_is_ggtt(vm) && vm->mm.color_adjust;
365 }
366 
367 static inline struct i915_ggtt *
368 i915_vm_to_ggtt(struct i915_address_space *vm)
369 {
370 	BUILD_BUG_ON(offsetof(struct i915_ggtt, vm));
371 	GEM_BUG_ON(!i915_is_ggtt(vm));
372 	return container_of(vm, struct i915_ggtt, vm);
373 }
374 
375 static inline struct i915_ppgtt *
376 i915_vm_to_ppgtt(struct i915_address_space *vm)
377 {
378 	BUILD_BUG_ON(offsetof(struct i915_ppgtt, vm));
379 	GEM_BUG_ON(i915_is_ggtt(vm));
380 	return container_of(vm, struct i915_ppgtt, vm);
381 }
382 
383 static inline struct i915_address_space *
384 i915_vm_get(struct i915_address_space *vm)
385 {
386 	kref_get(&vm->ref);
387 	return vm;
388 }
389 
390 void i915_vm_release(struct kref *kref);
391 
392 static inline void i915_vm_put(struct i915_address_space *vm)
393 {
394 	kref_put(&vm->ref, i915_vm_release);
395 }
396 
397 static inline struct i915_address_space *
398 i915_vm_open(struct i915_address_space *vm)
399 {
400 	GEM_BUG_ON(!atomic_read(&vm->open));
401 	atomic_inc(&vm->open);
402 	return i915_vm_get(vm);
403 }
404 
405 static inline bool
406 i915_vm_tryopen(struct i915_address_space *vm)
407 {
408 	if (atomic_add_unless(&vm->open, 1, 0))
409 		return i915_vm_get(vm);
410 
411 	return false;
412 }
413 
414 void __i915_vm_close(struct i915_address_space *vm);
415 
416 static inline void
417 i915_vm_close(struct i915_address_space *vm)
418 {
419 	GEM_BUG_ON(!atomic_read(&vm->open));
420 	__i915_vm_close(vm);
421 
422 	i915_vm_put(vm);
423 }
424 
425 void i915_address_space_init(struct i915_address_space *vm, int subclass);
426 void i915_address_space_fini(struct i915_address_space *vm);
427 
428 static inline u32 i915_pte_index(u64 address, unsigned int pde_shift)
429 {
430 	const u32 mask = NUM_PTE(pde_shift) - 1;
431 
432 	return (address >> PAGE_SHIFT) & mask;
433 }
434 
435 /*
436  * Helper to counts the number of PTEs within the given length. This count
437  * does not cross a page table boundary, so the max value would be
438  * GEN6_PTES for GEN6, and GEN8_PTES for GEN8.
439  */
440 static inline u32 i915_pte_count(u64 addr, u64 length, unsigned int pde_shift)
441 {
442 	const u64 mask = ~((1ULL << pde_shift) - 1);
443 	u64 end;
444 
445 	GEM_BUG_ON(length == 0);
446 	GEM_BUG_ON(offset_in_page(addr | length));
447 
448 	end = addr + length;
449 
450 	if ((addr & mask) != (end & mask))
451 		return NUM_PTE(pde_shift) - i915_pte_index(addr, pde_shift);
452 
453 	return i915_pte_index(end, pde_shift) - i915_pte_index(addr, pde_shift);
454 }
455 
456 static inline u32 i915_pde_index(u64 addr, u32 shift)
457 {
458 	return (addr >> shift) & I915_PDE_MASK;
459 }
460 
461 static inline struct i915_page_table *
462 i915_pt_entry(const struct i915_page_directory * const pd,
463 	      const unsigned short n)
464 {
465 	return pd->entry[n];
466 }
467 
468 static inline struct i915_page_directory *
469 i915_pd_entry(const struct i915_page_directory * const pdp,
470 	      const unsigned short n)
471 {
472 	return pdp->entry[n];
473 }
474 
475 static inline dma_addr_t
476 i915_page_dir_dma_addr(const struct i915_ppgtt *ppgtt, const unsigned int n)
477 {
478 	struct i915_page_table *pt = ppgtt->pd->entry[n];
479 
480 	return __px_dma(pt ? px_base(pt) : ppgtt->vm.scratch[ppgtt->vm.top]);
481 }
482 
483 void ppgtt_init(struct i915_ppgtt *ppgtt, struct intel_gt *gt);
484 
485 int i915_ggtt_probe_hw(struct drm_i915_private *i915);
486 int i915_ggtt_init_hw(struct drm_i915_private *i915);
487 int i915_ggtt_enable_hw(struct drm_i915_private *i915);
488 void i915_ggtt_enable_guc(struct i915_ggtt *ggtt);
489 void i915_ggtt_disable_guc(struct i915_ggtt *ggtt);
490 int i915_init_ggtt(struct drm_i915_private *i915);
491 void i915_ggtt_driver_release(struct drm_i915_private *i915);
492 
493 static inline bool i915_ggtt_has_aperture(const struct i915_ggtt *ggtt)
494 {
495 	return ggtt->mappable_end > 0;
496 }
497 
498 int i915_ppgtt_init_hw(struct intel_gt *gt);
499 
500 struct i915_ppgtt *i915_ppgtt_create(struct intel_gt *gt);
501 
502 void i915_ggtt_suspend(struct i915_ggtt *gtt);
503 void i915_ggtt_resume(struct i915_ggtt *ggtt);
504 
505 #define kmap_atomic_px(px) kmap_atomic(__px_page(px_base(px)))
506 
507 void
508 fill_page_dma(struct drm_i915_gem_object *p, const u64 val, unsigned int count);
509 
510 #define fill_px(px, v) fill_page_dma(px_base(px), (v), PAGE_SIZE / sizeof(u64))
511 #define fill32_px(px, v) do {						\
512 	u64 v__ = lower_32_bits(v);					\
513 	fill_px((px), v__ << 32 | v__);					\
514 } while (0)
515 
516 int setup_scratch_page(struct i915_address_space *vm);
517 void free_scratch(struct i915_address_space *vm);
518 
519 struct drm_i915_gem_object *alloc_pt_dma(struct i915_address_space *vm, int sz);
520 struct i915_page_table *alloc_pt(struct i915_address_space *vm);
521 struct i915_page_directory *alloc_pd(struct i915_address_space *vm);
522 struct i915_page_directory *__alloc_pd(int npde);
523 
524 int pin_pt_dma(struct i915_address_space *vm, struct drm_i915_gem_object *obj);
525 
526 void free_px(struct i915_address_space *vm,
527 	     struct i915_page_table *pt, int lvl);
528 #define free_pt(vm, px) free_px(vm, px, 0)
529 #define free_pd(vm, px) free_px(vm, px_pt(px), 1)
530 
531 void
532 __set_pd_entry(struct i915_page_directory * const pd,
533 	       const unsigned short idx,
534 	       struct i915_page_table *pt,
535 	       u64 (*encode)(const dma_addr_t, const enum i915_cache_level));
536 
537 #define set_pd_entry(pd, idx, to) \
538 	__set_pd_entry((pd), (idx), px_pt(to), gen8_pde_encode)
539 
540 void
541 clear_pd_entry(struct i915_page_directory * const pd,
542 	       const unsigned short idx,
543 	       const struct drm_i915_gem_object * const scratch);
544 
545 bool
546 release_pd_entry(struct i915_page_directory * const pd,
547 		 const unsigned short idx,
548 		 struct i915_page_table * const pt,
549 		 const struct drm_i915_gem_object * const scratch);
550 void gen6_ggtt_invalidate(struct i915_ggtt *ggtt);
551 
552 int ggtt_set_pages(struct i915_vma *vma);
553 int ppgtt_set_pages(struct i915_vma *vma);
554 void clear_pages(struct i915_vma *vma);
555 
556 void ppgtt_bind_vma(struct i915_address_space *vm,
557 		    struct i915_vm_pt_stash *stash,
558 		    struct i915_vma *vma,
559 		    enum i915_cache_level cache_level,
560 		    u32 flags);
561 void ppgtt_unbind_vma(struct i915_address_space *vm,
562 		      struct i915_vma *vma);
563 
564 void gtt_write_workarounds(struct intel_gt *gt);
565 
566 void setup_private_pat(struct intel_uncore *uncore);
567 
568 int i915_vm_alloc_pt_stash(struct i915_address_space *vm,
569 			   struct i915_vm_pt_stash *stash,
570 			   u64 size);
571 int i915_vm_pin_pt_stash(struct i915_address_space *vm,
572 			 struct i915_vm_pt_stash *stash);
573 void i915_vm_free_pt_stash(struct i915_address_space *vm,
574 			   struct i915_vm_pt_stash *stash);
575 
576 struct i915_vma *
577 __vm_create_scratch_for_read(struct i915_address_space *vm, unsigned long size);
578 
579 static inline struct sgt_dma {
580 	struct scatterlist *sg;
581 	dma_addr_t dma, max;
582 } sgt_dma(struct i915_vma *vma) {
583 	struct scatterlist *sg = vma->pages->sgl;
584 	dma_addr_t addr = sg_dma_address(sg);
585 
586 	return (struct sgt_dma){ sg, addr, addr + sg_dma_len(sg) };
587 }
588 
589 #endif
590