From 34e8548168758f1adf50984f40ce190e5c19c621 Mon Sep 17 00:00:00 2001 From: Marek Szyprowski Date: Fri, 8 May 2020 16:10:16 +0200 Subject: 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 Reviewed-by: Laurent Pinchart --- drivers/gpu/drm/rcar-du/rcar_du_vsp.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) (limited to 'drivers/gpu/drm/rcar-du') 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; } } -- cgit v1.2.3