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/rockchip/rockchip_drm_gem.c | 26 ++++++++++++--------------
1 file changed, 12 insertions(+), 14 deletions(-)
diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_gem.c b/drivers/gpu/drm/rockchip/rockchip_drm_gem.c
index 0d18846..9df7d7d 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_gem.c
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_gem.c
@@ -36,8 +36,8 @@ static int rockchip_gem_iommu_map(struct rockchip_gem_object *rk_obj)
rk_obj->dma_addr = rk_obj->mm.start;
- ret = iommu_map_sg(private->domain, rk_obj->dma_addr, rk_obj->sgt->sgl,
- rk_obj->sgt->nents, prot);
+ ret = iommu_map_sgtable(private->domain, rk_obj->dma_addr, rk_obj->sgt,
+ prot);
if (ret < rk_obj->base.size) {
DRM_ERROR("failed to map buffer: size=%zd request_size=%zd\n",
ret, rk_obj->base.size);
@@ -98,11 +98,10 @@ static int rockchip_gem_get_pages(struct rockchip_gem_object *rk_obj)
* TODO: Replace this by drm_clflush_sg() once it can be implemented
* without relying on symbols that are not exported.
*/
- for_each_sg(rk_obj->sgt->sgl, s, rk_obj->sgt->nents, i)
+ for_each_sg(rk_obj->sgt->sgl, s, rk_obj->sgt->orig_nents, i)
sg_dma_address(s) = sg_phys(s);
- dma_sync_sg_for_device(drm->dev, rk_obj->sgt->sgl, rk_obj->sgt->nents,
- DMA_TO_DEVICE);
+ dma_sync_sgtable_for_device(drm->dev, rk_obj->sgt, DMA_TO_DEVICE);
return 0;
@@ -350,8 +349,8 @@ void rockchip_gem_free_object(struct drm_gem_object *obj)
if (private->domain) {
rockchip_gem_iommu_unmap(rk_obj);
} else {
- dma_unmap_sg(drm->dev, rk_obj->sgt->sgl,
- rk_obj->sgt->nents, DMA_BIDIRECTIONAL);
+ dma_unmap_sgtable(drm->dev, rk_obj->sgt,
+ DMA_BIDIRECTIONAL);
}
drm_prime_gem_destroy(obj, rk_obj->sgt);
} else {
@@ -493,15 +492,14 @@ static unsigned long rockchip_sg_get_contiguous_size(struct sg_table *sgt,
struct sg_table *sg,
struct rockchip_gem_object *rk_obj)
{
- int count = dma_map_sg(drm->dev, sg->sgl, sg->nents,
- DMA_BIDIRECTIONAL);
- if (!count)
- return -EINVAL;
+ int err = dma_map_sgtable(drm->dev, sg, DMA_BIDIRECTIONAL);
+ if (err)
+ return err;
- if (rockchip_sg_get_contiguous_size(sg, count) < attach->dmabuf->size) {
+ if (rockchip_sg_get_contiguous_size(sg, sg->nents) <
+ attach->dmabuf->size) {
DRM_ERROR("failed to map sg_table to contiguous linear address.\n");
- dma_unmap_sg(drm->dev, sg->sgl, sg->nents,
- DMA_BIDIRECTIONAL);
+ dma_unmap_sgtable(drm->dev, sg, DMA_BIDIRECTIONAL);
return -EINVAL;
}
--
1.9.1
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