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/tegra/gem.c | 27 ++++++++++-----------------
drivers/gpu/drm/tegra/plane.c | 15 +++++----------
2 files changed, 15 insertions(+), 27 deletions(-)
diff --git a/drivers/gpu/drm/tegra/gem.c b/drivers/gpu/drm/tegra/gem.c
index 6237681..4554fbb 100644
--- a/drivers/gpu/drm/tegra/gem.c
+++ b/drivers/gpu/drm/tegra/gem.c
@@ -98,8 +98,8 @@ static struct sg_table *tegra_bo_pin(struct device *dev, struct host1x_bo *bo,
* the SG table needs to be copied to avoid overwriting any
* other potential users of the original SG table.
*/
- err = sg_alloc_table_from_sg(sgt, obj->sgt->sgl, obj->sgt->nents,
- GFP_KERNEL);
+ err = sg_alloc_table_from_sg(sgt, obj->sgt->sgl,
+ obj->sgt->orig_nents, GFP_KERNEL);
if (err < 0)
goto free;
} else {
@@ -196,8 +196,7 @@ static int tegra_bo_iommu_map(struct tegra_drm *tegra, struct tegra_bo *bo)
bo->iova = bo->mm->start;
- bo->size = iommu_map_sg(tegra->domain, bo->iova, bo->sgt->sgl,
- bo->sgt->nents, prot);
+ bo->size = iommu_map_sgtable(tegra->domain, bo->iova, bo->sgt, prot);
if (!bo->size) {
dev_err(tegra->drm->dev, "failed to map buffer\n");
err = -ENOMEM;
@@ -264,8 +263,7 @@ static struct tegra_bo *tegra_bo_alloc_object(struct drm_device *drm,
static void tegra_bo_free(struct drm_device *drm, struct tegra_bo *bo)
{
if (bo->pages) {
- dma_unmap_sg(drm->dev, bo->sgt->sgl, bo->sgt->nents,
- DMA_FROM_DEVICE);
+ dma_unmap_sgtable(drm->dev, bo->sgt, DMA_FROM_DEVICE);
drm_gem_put_pages(&bo->gem, bo->pages, true, true);
sg_free_table(bo->sgt);
kfree(bo->sgt);
@@ -290,12 +288,9 @@ static int tegra_bo_get_pages(struct drm_device *drm, struct tegra_bo *bo)
goto put_pages;
}
- err = dma_map_sg(drm->dev, bo->sgt->sgl, bo->sgt->nents,
- DMA_FROM_DEVICE);
- if (err == 0) {
- err = -EFAULT;
+ err = dma_map_sgtable(drm->dev, bo->sgt, DMA_FROM_DEVICE);
+ if (err)
goto free_sgt;
- }
return 0;
@@ -571,7 +566,7 @@ int tegra_drm_mmap(struct file *file, struct vm_area_struct *vma)
goto free;
}
- if (dma_map_sg(attach->dev, sgt->sgl, sgt->nents, dir) == 0)
+ if (dma_map_sgtable(attach->dev, sgt, dir))
goto free;
return sgt;
@@ -590,7 +585,7 @@ static void tegra_gem_prime_unmap_dma_buf(struct dma_buf_attachment *attach,
struct tegra_bo *bo = to_tegra_bo(gem);
if (bo->pages)
- dma_unmap_sg(attach->dev, sgt->sgl, sgt->nents, dir);
+ dma_unmap_sgtable(attach->dev, sgt, dir);
sg_free_table(sgt);
kfree(sgt);
@@ -609,8 +604,7 @@ static int tegra_gem_prime_begin_cpu_access(struct dma_buf *buf,
struct drm_device *drm = gem->dev;
if (bo->pages)
- dma_sync_sg_for_cpu(drm->dev, bo->sgt->sgl, bo->sgt->nents,
- DMA_FROM_DEVICE);
+ dma_sync_sgtable_for_cpu(drm->dev, bo->sgt, DMA_FROM_DEVICE);
return 0;
}
@@ -623,8 +617,7 @@ static int tegra_gem_prime_end_cpu_access(struct dma_buf *buf,
struct drm_device *drm = gem->dev;
if (bo->pages)
- dma_sync_sg_for_device(drm->dev, bo->sgt->sgl, bo->sgt->nents,
- DMA_TO_DEVICE);
+ dma_sync_sgtable_for_device(drm->dev, bo->sgt, DMA_TO_DEVICE);
return 0;
}
diff --git a/drivers/gpu/drm/tegra/plane.c b/drivers/gpu/drm/tegra/plane.c
index 9ccfb56..4b1c2ae6 100644
--- a/drivers/gpu/drm/tegra/plane.c
+++ b/drivers/gpu/drm/tegra/plane.c
@@ -130,12 +130,9 @@ static int tegra_dc_pin(struct tegra_dc *dc, struct tegra_plane_state *state)
}
if (sgt) {
- err = dma_map_sg(dc->dev, sgt->sgl, sgt->nents,
- DMA_TO_DEVICE);
- if (err == 0) {
- err = -ENOMEM;
+ err = dma_map_sgtable(dc->dev, sgt, DMA_TO_DEVICE);
+ if (err)
goto unpin;
- }
/*
* The display controller needs contiguous memory, so
@@ -143,7 +140,7 @@ static int tegra_dc_pin(struct tegra_dc *dc, struct tegra_plane_state *state)
* map its SG table to a single contiguous chunk of
* I/O virtual memory.
*/
- if (err > 1) {
+ if (sgt->nents > 1) {
err = -EINVAL;
goto unpin;
}
@@ -165,8 +162,7 @@ static int tegra_dc_pin(struct tegra_dc *dc, struct tegra_plane_state *state)
struct sg_table *sgt = state->sgt[i];
if (sgt)
- dma_unmap_sg(dc->dev, sgt->sgl, sgt->nents,
- DMA_TO_DEVICE);
+ dma_unmap_sgtable(dc->dev, sgt, DMA_TO_DEVICE);
host1x_bo_unpin(dc->dev, &bo->base, sgt);
state->iova[i] = DMA_MAPPING_ERROR;
@@ -185,8 +181,7 @@ static void tegra_dc_unpin(struct tegra_dc *dc, struct tegra_plane_state *state)
struct sg_table *sgt = state->sgt[i];
if (sgt)
- dma_unmap_sg(dc->dev, sgt->sgl, sgt->nents,
- DMA_TO_DEVICE);
+ dma_unmap_sgtable(dc->dev, sgt, DMA_TO_DEVICE);
host1x_bo_unpin(dc->dev, &bo->base, sgt);
state->iova[i] = DMA_MAPPING_ERROR;
--
1.9.1
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