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/msm/msm_gem.c | 13 +++++--------
drivers/gpu/drm/msm/msm_iommu.c | 2 +-
2 files changed, 6 insertions(+), 9 deletions(-)
diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c
index 5a6a79f..ab952d6 100644
--- a/drivers/gpu/drm/msm/msm_gem.c
+++ b/drivers/gpu/drm/msm/msm_gem.c
@@ -53,11 +53,10 @@ static void sync_for_device(struct msm_gem_object *msm_obj)
struct device *dev = msm_obj->base.dev->dev;
if (get_dma_ops(dev) && IS_ENABLED(CONFIG_ARM64)) {
- dma_sync_sg_for_device(dev, msm_obj->sgt->sgl,
- msm_obj->sgt->nents, DMA_BIDIRECTIONAL);
+ dma_sync_sgtable_for_device(dev, msm_obj->sgt,
+ DMA_BIDIRECTIONAL);
} else {
- dma_map_sg(dev, msm_obj->sgt->sgl,
- msm_obj->sgt->nents, DMA_BIDIRECTIONAL);
+ dma_map_sgtable(dev, msm_obj->sgt, DMA_BIDIRECTIONAL);
}
}
@@ -66,11 +65,9 @@ static void sync_for_cpu(struct msm_gem_object *msm_obj)
struct device *dev = msm_obj->base.dev->dev;
if (get_dma_ops(dev) && IS_ENABLED(CONFIG_ARM64)) {
- dma_sync_sg_for_cpu(dev, msm_obj->sgt->sgl,
- msm_obj->sgt->nents, DMA_BIDIRECTIONAL);
+ dma_sync_sgtable_for_cpu(dev, msm_obj->sgt, DMA_BIDIRECTIONAL);
} else {
- dma_unmap_sg(dev, msm_obj->sgt->sgl,
- msm_obj->sgt->nents, DMA_BIDIRECTIONAL);
+ dma_unmap_sgtable(dev, msm_obj->sgt, DMA_BIDIRECTIONAL);
}
}
diff --git a/drivers/gpu/drm/msm/msm_iommu.c b/drivers/gpu/drm/msm/msm_iommu.c
index ad58cfe..d322b39 100644
--- a/drivers/gpu/drm/msm/msm_iommu.c
+++ b/drivers/gpu/drm/msm/msm_iommu.c
@@ -43,7 +43,7 @@ static int msm_iommu_map(struct msm_mmu *mmu, uint64_t iova,
struct msm_iommu *iommu = to_msm_iommu(mmu);
size_t ret;
- ret = iommu_map_sg(iommu->domain, iova, sgt->sgl, sgt->nents, prot);
+ ret = iommu_map_sgtable(iommu->domain, iova, sgt, prot);
WARN_ON(!ret);
return (ret == len) ? 0 : -EINVAL;
--
1.9.1
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