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author | Marek Szyprowski <m.szyprowski@samsung.com> | 2020-05-11 12:27:54 +0200 |
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committer | Marek Szyprowski <m.szyprowski@samsung.com> | 2020-09-10 08:17:48 +0200 |
commit | 6c6fa39ca958d5313ff90d3e6c3064e0043c1da3 (patch) | |
tree | bf3ae1419f202c5c78db606fbed19b5471075603 /drivers/gpu/drm/drm_cache.c | |
parent | 0552daac2d18fc92c71c94492476b8eb521227e9 (diff) | |
download | linux-stable-6c6fa39ca958d5313ff90d3e6c3064e0043c1da3.tar.gz linux-stable-6c6fa39ca958d5313ff90d3e6c3064e0043c1da3.tar.bz2 linux-stable-6c6fa39ca958d5313ff90d3e6c3064e0043c1da3.zip |
drm: core: 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: Andrzej Hajda <a.hajda@samsung.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Diffstat (limited to 'drivers/gpu/drm/drm_cache.c')
-rw-r--r-- | drivers/gpu/drm/drm_cache.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/gpu/drm/drm_cache.c b/drivers/gpu/drm/drm_cache.c index 03e01b000f7a..0fe3c496002a 100644 --- a/drivers/gpu/drm/drm_cache.c +++ b/drivers/gpu/drm/drm_cache.c @@ -127,7 +127,7 @@ drm_clflush_sg(struct sg_table *st) struct sg_page_iter sg_iter; mb(); /*CLFLUSH is ordered only by using memory barriers*/ - for_each_sg_page(st->sgl, &sg_iter, st->nents, 0) + for_each_sgtable_page(st, &sg_iter, 0) drm_clflush_page(sg_page_iter_page(&sg_iter)); mb(); /*Make sure that all cache line entry is flushed*/ |