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
 13bool 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 */
 53struct 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