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/*
* SPDX-License-Identifier: MIT
*
* Copyright © 2016 Intel Corporation
*/
#include "i915_scatterlist.h"
#include <drm/drm_mm.h>
#include <linux/slab.h>
bool i915_sg_trim(struct sg_table *orig_st)
{
struct sg_table new_st;
struct scatterlist *sg, *new_sg;
unsigned int i;
if (orig_st->nents == orig_st->orig_nents)
return false;
if (sg_alloc_table(&new_st, orig_st->nents, GFP_KERNEL | __GFP_NOWARN))
return false;
new_sg = new_st.sgl;
for_each_sg(orig_st->sgl, sg, orig_st->nents, i) {
sg_set_page(new_sg, sg_page(sg), sg->length, 0);
sg_dma_address(new_sg) = sg_dma_address(sg);
sg_dma_len(new_sg) = sg_dma_len(sg);
new_sg = sg_next(new_sg);
}
GEM_BUG_ON(new_sg); /* Should walk exactly nents and hit the end */
sg_free_table(orig_st);
*orig_st = new_st;
return true;
}
/**
* i915_sg_from_mm_node - Create an sg_table from a struct drm_mm_node
* @node: The drm_mm_node.
* @region_start: An offset to add to the dma addresses of the sg list.
*
* Create a struct sg_table, initializing it from a struct drm_mm_node,
* taking a maximum segment length into account, splitting into segments
* if necessary.
*
* Return: A pointer to a kmalloced struct sg_table on success, negative
* error code cast to an error pointer on failure.
*/
struct sg_table *i915_sg_from_mm_node(const struct drm_mm_node *node,
u64 region_start)
{
const u64 max_segment = SZ_1G; /* Do we have a limit on this? */
u64 segment_pages = max_segment >> PAGE_SHIFT;
u64 block_size, offset, prev_end;
struct sg_table *st;
struct scatterlist *sg;
st = kmalloc(sizeof(*st), GFP_KERNEL);
if (!st)
return ERR_PTR(-ENOMEM);
if (sg_alloc_table(st, DIV_ROUND_UP(node->size, segment_pages),
GFP_KERNEL)) {
kfree(st);
return ERR_PTR(-ENOMEM);
}
sg = st->sgl;
st->nents = 0;
prev_end = (resource_size_t)-1;
block_size = node->size << PAGE_SHIFT;
offset = node->start << PAGE_SHIFT;
while (block_size) {
u64 len;
if (offset != prev_end || sg->length >= max_segment) {
if (st->nents)
sg = __sg_next(sg);
sg_dma_address(sg) = region_start + offset;
sg_dma_len(sg) = 0;
sg->length = 0;
st->nents++;
}
len = min(block_size, max_segment - sg->length);
sg->length += len;
sg_dma_len(sg) += len;
offset += len;
block_size -= len;
prev_end = offset;
}
sg_mark_end(sg);
i915_sg_trim(st);
return st;
}
#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
#include "selftests/scatterlist.c"
#endif
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