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author | Marek Szyprowski <m.szyprowski@samsung.com> | 2020-04-28 14:08:07 +0300 |
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committer | Marek Szyprowski <m.szyprowski@samsung.com> | 2020-09-10 09:17:48 +0300 |
commit | efcb3730ef4b2911bbe98a686468a5173c786150 (patch) | |
tree | 18e539cdac7bb8ec6d8078d6d39635485102a8d6 | |
parent | 6c6fa39ca958d5313ff90d3e6c3064e0043c1da3 (diff) | |
download | linux-efcb3730ef4b2911bbe98a686468a5173c786150.tar.xz |
drm: armada: 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>
-rw-r--r-- | drivers/gpu/drm/armada/armada_gem.c | 24 |
1 files changed, 11 insertions, 13 deletions
diff --git a/drivers/gpu/drm/armada/armada_gem.c b/drivers/gpu/drm/armada/armada_gem.c index 8005614d2e6b..a63008ce284d 100644 --- a/drivers/gpu/drm/armada/armada_gem.c +++ b/drivers/gpu/drm/armada/armada_gem.c @@ -379,7 +379,7 @@ armada_gem_prime_map_dma_buf(struct dma_buf_attachment *attach, struct armada_gem_object *dobj = drm_to_armada_gem(obj); struct scatterlist *sg; struct sg_table *sgt; - int i, num; + int i; sgt = kmalloc(sizeof(*sgt), GFP_KERNEL); if (!sgt) @@ -395,22 +395,18 @@ armada_gem_prime_map_dma_buf(struct dma_buf_attachment *attach, mapping = dobj->obj.filp->f_mapping; - for_each_sg(sgt->sgl, sg, count, i) { + for_each_sgtable_sg(sgt, sg, i) { struct page *page; page = shmem_read_mapping_page(mapping, i); - if (IS_ERR(page)) { - num = i; + if (IS_ERR(page)) goto release; - } sg_set_page(sg, page, PAGE_SIZE, 0); } - if (dma_map_sg(attach->dev, sgt->sgl, sgt->nents, dir) == 0) { - num = sgt->nents; + if (dma_map_sgtable(attach->dev, sgt, dir, 0)) goto release; - } } else if (dobj->page) { /* Single contiguous page */ if (sg_alloc_table(sgt, 1, GFP_KERNEL)) @@ -418,7 +414,7 @@ armada_gem_prime_map_dma_buf(struct dma_buf_attachment *attach, sg_set_page(sgt->sgl, dobj->page, dobj->obj.size, 0); - if (dma_map_sg(attach->dev, sgt->sgl, sgt->nents, dir) == 0) + if (dma_map_sgtable(attach->dev, sgt, dir, 0)) goto free_table; } else if (dobj->linear) { /* Single contiguous physical region - no struct page */ @@ -432,8 +428,9 @@ armada_gem_prime_map_dma_buf(struct dma_buf_attachment *attach, return sgt; release: - for_each_sg(sgt->sgl, sg, num, i) - put_page(sg_page(sg)); + for_each_sgtable_sg(sgt, sg, i) + if (sg_page(sg)) + put_page(sg_page(sg)); free_table: sg_free_table(sgt); free_sgt: @@ -449,11 +446,12 @@ static void armada_gem_prime_unmap_dma_buf(struct dma_buf_attachment *attach, int i; if (!dobj->linear) - dma_unmap_sg(attach->dev, sgt->sgl, sgt->nents, dir); + dma_unmap_sgtable(attach->dev, sgt, dir, 0); if (dobj->obj.filp) { struct scatterlist *sg; - for_each_sg(sgt->sgl, sg, sgt->nents, i) + + for_each_sgtable_sg(sgt, sg, i) put_page(sg_page(sg)); } |