diff options
author | Marek Szyprowski <m.szyprowski@samsung.com> | 2020-06-19 12:36:04 +0200 |
---|---|---|
committer | Christian König <christian.koenig@amd.com> | 2020-07-13 10:47:26 +0200 |
commit | 39913934e67cab214480cc95a3632696aeb8e71a (patch) | |
tree | 25657913c7576678174eed382d629f677a704899 /drivers/gpu/drm/radeon | |
parent | drm/lima: Expose job_hang_limit module parameter (diff) | |
download | linux-39913934e67cab214480cc95a3632696aeb8e71a.tar.xz linux-39913934e67cab214480cc95a3632696aeb8e71a.zip |
drm: amdgpu: fix common struct sg_table related issues
The Documentation/DMA-API-HOWTO.txt states that the dma_map_sg() function
returns the number of the created entries in the DMA address space.
However the subsequent calls to the dma_sync_sg_for_{device,cpu}() and
dma_unmap_sg must be called with the original number of the entries
passed to the dma_map_sg().
struct sg_table is a common structure used for describing a non-contiguous
memory buffer, used commonly in the DRM and graphics subsystems. It
consists of a scatterlist with memory pages and DMA addresses (sgl entry),
as well as the number of scatterlist entries: CPU pages (orig_nents entry)
and DMA mapped pages (nents entry).
It turned out that it was a common mistake to misuse nents and orig_nents
entries, calling DMA-mapping functions with a wrong number of entries or
ignoring the number of mapped entries returned by the dma_map_sg()
function.
To avoid such issues, lets use a common dma-mapping wrappers operating
directly on the struct sg_table objects and use scatterlist page
iterators where possible. This, almost always, hides references to the
nents and orig_nents entries, making the code robust, easier to follow
and copy/paste safe.
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/371142/
Signed-off-by: Christian König <christian.koenig@amd.com>
Diffstat (limited to 'drivers/gpu/drm/radeon')
0 files changed, 0 insertions, 0 deletions