The Documentation/DMA-API-HOWTO.txt states that dma_map_sg returns the
numer of the created entries in the DMA address space. However the
subsequent calls to dma_sync_sg_for_{device,cpu} and dma_unmap_sg must be
called with the original number of the entries passed to dma_map_sg. The
sg_table->nents in turn holds the result of the dma_map_sg call as stated
in include/linux/scatterlist.h. A common mistake was to ignore a result
of the dma_map_sg function and don't use the sg_table->orig_nents at all.
To avoid such issues, lets use common dma-mapping wrappers operating
directly on the struct sg_table objects and adjust references to the
nents and orig_nents respectively.
Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
---
For more information, see '[PATCH v3 00/25] DRM: fix struct sg_table nents
vs. orig_nents misuse' thread: https://lkml.org/lkml/2020/5/5/187
---
drivers/gpu/drm/exynos/exynos_drm_g2d.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/exynos/exynos_drm_g2d.c b/drivers/gpu/drm/exynos/exynos_drm_g2d.c
index fcee33a..6a655d3 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_g2d.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_g2d.c
@@ -395,8 +395,8 @@ static void g2d_userptr_put_dma_addr(struct g2d_data *g2d,
return;
out:
- dma_unmap_sg(to_dma_dev(g2d->drm_dev), g2d_userptr->sgt->sgl,
- g2d_userptr->sgt->nents, DMA_BIDIRECTIONAL);
+ dma_unmap_sgtable(to_dma_dev(g2d->drm_dev), g2d_userptr->sgt,
+ DMA_BIDIRECTIONAL);
pages = frame_vector_pages(g2d_userptr->vec);
if (!IS_ERR(pages)) {
@@ -511,10 +511,9 @@ static dma_addr_t *g2d_userptr_get_dma_addr(struct g2d_data *g2d,
g2d_userptr->sgt = sgt;
- if (!dma_map_sg(to_dma_dev(g2d->drm_dev), sgt->sgl, sgt->nents,
- DMA_BIDIRECTIONAL)) {
+ ret = dma_map_sgtable(to_dma_dev(g2d->drm_dev), sgt, DMA_BIDIRECTIONAL);
+ if (ret) {
DRM_DEV_ERROR(g2d->dev, "failed to map sgt with dma region.\n");
- ret = -ENOMEM;
goto err_sg_free_table;
}
--
1.9.1
_______________________________________________
dri-devel mailing list
dri-devel@xxxxxxxxxxxxxxxxxxxxx
https://lists.freedesktop.org/mailman/listinfo/dri-devel
