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drm/prime: fix extracting of the DMA addresses from a scatterlist

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Scatterlist elements contains both pages and DMA addresses, but one
should not assume 1:1 relation between them. The sg->length is the size
of the physical memory chunk described by the sg->page, while
sg_dma_len(sg) is the size of the DMA (IO virtual) chunk described by
the sg_dma_address(sg).

The proper way of extracting both: pages and DMA addresses of the whole
buffer described by a scatterlist it to iterate independently over the
sg->pages/sg->length and sg_dma_address(sg)/sg_dma_len(sg) entries.

Fixes: 42e67b479e ("drm/prime: use dma length macro when mapping sg")
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200327162126.29705-1-m.szyprowski@samsung.com
Cc: stable@vger.kernel.org
This commit is contained in:
Marek Szyprowski 2020-03-27 17:21:26 +01:00 committed by Alex Deucher
parent cc46c03397
commit c0f83d164f
1 changed files with 25 additions and 12 deletions
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37
drivers/gpu/drm/drm_prime.c
View File

@ -962,27 +962,40 @@ int drm_prime_sg_to_page_addr_arrays(struct sg_table *sgt, struct page **pages,
unsigned count;
struct scatterlist *sg;
struct page *page;
u32 len, index;
u32 page_len, page_index;
dma_addr_t addr;
u32 dma_len, dma_index;
index = 0;
/*
* Scatterlist elements contains both pages and DMA addresses, but
* one shoud not assume 1:1 relation between them. The sg->length is
* the size of the physical memory chunk described by the sg->page,
* while sg_dma_len(sg) is the size of the DMA (IO virtual) chunk
* described by the sg_dma_address(sg).
*/
page_index = 0;
dma_index = 0;
for_each_sg(sgt->sgl, sg, sgt->nents, count) {
len = sg_dma_len(sg);
page_len = sg->length;
page = sg_page(sg);
dma_len = sg_dma_len(sg);
addr = sg_dma_address(sg);
while (len > 0) {
if (WARN_ON(index >= max_entries))
while (pages && page_len > 0) {
if (WARN_ON(page_index >= max_entries))
return -1;
if (pages)
pages[index] = page;
if (addrs)
addrs[index] = addr;
pages[page_index] = page;
page++;
page_len -= PAGE_SIZE;
page_index++;
}
while (addrs && dma_len > 0) {
if (WARN_ON(dma_index >= max_entries))
return -1;
addrs[dma_index] = addr;
addr += PAGE_SIZE;
len -= PAGE_SIZE;
index++;
dma_len -= PAGE_SIZE;
dma_index++;
}
}
return 0;