1 /* 2 * SPDX-License-Identifier: MIT 3 * 4 * Copyright © 2016 Intel Corporation 5 */ 6 7 #include "i915_scatterlist.h" 8 9 #include <drm/drm_mm.h> 10 11 #include <linux/slab.h> 12 13 bool i915_sg_trim(struct sg_table *orig_st) 14 { 15 struct sg_table new_st; 16 struct scatterlist *sg, *new_sg; 17 unsigned int i; 18 19 if (orig_st->nents == orig_st->orig_nents) 20 return false; 21 22 if (sg_alloc_table(&new_st, orig_st->nents, GFP_KERNEL | __GFP_NOWARN)) 23 return false; 24 25 new_sg = new_st.sgl; 26 for_each_sg(orig_st->sgl, sg, orig_st->nents, i) { 27 sg_set_page(new_sg, sg_page(sg), sg->length, 0); 28 sg_dma_address(new_sg) = sg_dma_address(sg); 29 sg_dma_len(new_sg) = sg_dma_len(sg); 30 31 new_sg = sg_next(new_sg); 32 } 33 GEM_BUG_ON(new_sg); /* Should walk exactly nents and hit the end */ 34 35 sg_free_table(orig_st); 36 37 *orig_st = new_st; 38 return true; 39 } 40 41 /** 42 * i915_sg_from_mm_node - Create an sg_table from a struct drm_mm_node 43 * @node: The drm_mm_node. 44 * @region_start: An offset to add to the dma addresses of the sg list. 45 * 46 * Create a struct sg_table, initializing it from a struct drm_mm_node, 47 * taking a maximum segment length into account, splitting into segments 48 * if necessary. 49 * 50 * Return: A pointer to a kmalloced struct sg_table on success, negative 51 * error code cast to an error pointer on failure. 52 */ 53 struct sg_table *i915_sg_from_mm_node(const struct drm_mm_node *node, 54 u64 region_start) 55 { 56 const u64 max_segment = SZ_1G; /* Do we have a limit on this? */ 57 u64 segment_pages = max_segment >> PAGE_SHIFT; 58 u64 block_size, offset, prev_end; 59 struct sg_table *st; 60 struct scatterlist *sg; 61 62 st = kmalloc(sizeof(*st), GFP_KERNEL); 63 if (!st) 64 return ERR_PTR(-ENOMEM); 65 66 if (sg_alloc_table(st, DIV_ROUND_UP(node->size, segment_pages), 67 GFP_KERNEL)) { 68 kfree(st); 69 return ERR_PTR(-ENOMEM); 70 } 71 72 sg = st->sgl; 73 st->nents = 0; 74 prev_end = (resource_size_t)-1; 75 block_size = node->size << PAGE_SHIFT; 76 offset = node->start << PAGE_SHIFT; 77 78 while (block_size) { 79 u64 len; 80 81 if (offset != prev_end || sg->length >= max_segment) { 82 if (st->nents) 83 sg = __sg_next(sg); 84 85 sg_dma_address(sg) = region_start + offset; 86 sg_dma_len(sg) = 0; 87 sg->length = 0; 88 st->nents++; 89 } 90 91 len = min(block_size, max_segment - sg->length); 92 sg->length += len; 93 sg_dma_len(sg) += len; 94 95 offset += len; 96 block_size -= len; 97 98 prev_end = offset; 99 } 100 101 sg_mark_end(sg); 102 i915_sg_trim(st); 103 104 return st; 105 } 106 107 #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST) 108 #include "selftests/scatterlist.c" 109 #endif 110