1 /*
2  * SPDX-License-Identifier: MIT
3  *
4  * Copyright © 2016 Intel Corporation
5  */
6 
7 #ifndef I915_SCATTERLIST_H
8 #define I915_SCATTERLIST_H
9 
10 #include <linux/pfn.h>
11 #include <linux/scatterlist.h>
12 #include <linux/swiotlb.h>
13 
14 #include "i915_gem.h"
15 
16 /*
17  * Optimised SGL iterator for GEM objects
18  */
19 static __always_inline struct sgt_iter {
20 	struct scatterlist *sgp;
21 	union {
22 		unsigned long pfn;
23 		dma_addr_t dma;
24 	};
25 	unsigned int curr;
26 	unsigned int max;
27 } __sgt_iter(struct scatterlist *sgl, bool dma) {
28 	struct sgt_iter s = { .sgp = sgl };
29 
30 	if (dma && s.sgp && sg_dma_len(s.sgp) == 0) {
31 		s.sgp = NULL;
32 	} else if (s.sgp) {
33 		s.max = s.curr = s.sgp->offset;
34 		if (dma) {
35 			s.dma = sg_dma_address(s.sgp);
36 			s.max += sg_dma_len(s.sgp);
37 		} else {
38 			s.pfn = page_to_pfn(sg_page(s.sgp));
39 			s.max += s.sgp->length;
40 		}
41 	}
42 
43 	return s;
44 }
45 
46 static inline int __sg_page_count(const struct scatterlist *sg)
47 {
48 	return sg->length >> PAGE_SHIFT;
49 }
50 
51 static inline int __sg_dma_page_count(const struct scatterlist *sg)
52 {
53 	return sg_dma_len(sg) >> PAGE_SHIFT;
54 }
55 
56 static inline struct scatterlist *____sg_next(struct scatterlist *sg)
57 {
58 	++sg;
59 	if (unlikely(sg_is_chain(sg)))
60 		sg = sg_chain_ptr(sg);
61 	return sg;
62 }
63 
64 /**
65  * __sg_next - return the next scatterlist entry in a list
66  * @sg:		The current sg entry
67  *
68  * Description:
69  *   If the entry is the last, return NULL; otherwise, step to the next
70  *   element in the array (@sg@+1). If that's a chain pointer, follow it;
71  *   otherwise just return the pointer to the current element.
72  **/
73 static inline struct scatterlist *__sg_next(struct scatterlist *sg)
74 {
75 	return sg_is_last(sg) ? NULL : ____sg_next(sg);
76 }
77 
78 /**
79  * __for_each_sgt_daddr - iterate over the device addresses of the given sg_table
80  * @__dp:	Device address (output)
81  * @__iter:	'struct sgt_iter' (iterator state, internal)
82  * @__sgt:	sg_table to iterate over (input)
83  * @__step:	step size
84  */
85 #define __for_each_sgt_daddr(__dp, __iter, __sgt, __step)		\
86 	for ((__iter) = __sgt_iter((__sgt)->sgl, true);			\
87 	     ((__dp) = (__iter).dma + (__iter).curr), (__iter).sgp;	\
88 	     (((__iter).curr += (__step)) >= (__iter).max) ?		\
89 	     (__iter) = __sgt_iter(__sg_next((__iter).sgp), true), 0 : 0)
90 
91 /**
92  * for_each_sgt_page - iterate over the pages of the given sg_table
93  * @__pp:	page pointer (output)
94  * @__iter:	'struct sgt_iter' (iterator state, internal)
95  * @__sgt:	sg_table to iterate over (input)
96  */
97 #define for_each_sgt_page(__pp, __iter, __sgt)				\
98 	for ((__iter) = __sgt_iter((__sgt)->sgl, false);		\
99 	     ((__pp) = (__iter).pfn == 0 ? NULL :			\
100 	      pfn_to_page((__iter).pfn + ((__iter).curr >> PAGE_SHIFT))); \
101 	     (((__iter).curr += PAGE_SIZE) >= (__iter).max) ?		\
102 	     (__iter) = __sgt_iter(__sg_next((__iter).sgp), false), 0 : 0)
103 
104 static inline unsigned int i915_sg_page_sizes(struct scatterlist *sg)
105 {
106 	unsigned int page_sizes;
107 
108 	page_sizes = 0;
109 	while (sg) {
110 		GEM_BUG_ON(sg->offset);
111 		GEM_BUG_ON(!IS_ALIGNED(sg->length, PAGE_SIZE));
112 		page_sizes |= sg->length;
113 		sg = __sg_next(sg);
114 	}
115 
116 	return page_sizes;
117 }
118 
119 static inline unsigned int i915_sg_segment_size(void)
120 {
121 	unsigned int size = swiotlb_max_segment();
122 
123 	if (size == 0)
124 		return SCATTERLIST_MAX_SEGMENT;
125 
126 	size = rounddown(size, PAGE_SIZE);
127 	/* swiotlb_max_segment_size can return 1 byte when it means one page. */
128 	if (size < PAGE_SIZE)
129 		size = PAGE_SIZE;
130 
131 	return size;
132 }
133 
134 bool i915_sg_trim(struct sg_table *orig_st);
135 
136 #endif
137