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authorMarek Szyprowski <m.szyprowski@samsung.com>2020-05-08 17:10:16 +0300
committerMarek Szyprowski <m.szyprowski@samsung.com>2020-09-10 09:18:35 +0300
commit34e8548168758f1adf50984f40ce190e5c19c621 (patch)
tree6f40e2f075e55149a1f953e68323c2609ab35a9e /drivers/gpu/drm/rcar-du
parent67ed9f9d95189d0f99c38f34b8bb1a8fa135c877 (diff)
downloadlinux-34e8548168758f1adf50984f40ce190e5c19c621.tar.xz
drm: rcar-du: 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. dma_map_sgtable() function returns zero or an error code, so adjust the return value check for the vsp1_du_map_sg() function. Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Diffstat (limited to 'drivers/gpu/drm/rcar-du')
-rw-r--r--drivers/gpu/drm/rcar-du/rcar_du_vsp.c3
1 files changed, 1 insertions, 2 deletions
diff --git a/drivers/gpu/drm/rcar-du/rcar_du_vsp.c b/drivers/gpu/drm/rcar-du/rcar_du_vsp.c
index f1a81c9b184d..a27bff999649 100644
--- a/drivers/gpu/drm/rcar-du/rcar_du_vsp.c
+++ b/drivers/gpu/drm/rcar-du/rcar_du_vsp.c
@@ -197,9 +197,8 @@ int rcar_du_vsp_map_fb(struct rcar_du_vsp *vsp, struct drm_framebuffer *fb,
goto fail;
ret = vsp1_du_map_sg(vsp->vsp, sgt);
- if (!ret) {
+ if (ret) {
sg_free_table(sgt);
- ret = -ENOMEM;
goto fail;
}
}