diff mbox series

[v9,18/32] drm: tegra: fix common struct sg_table related issues

Message ID 20200826063316.23486-19-m.szyprowski@samsung.com
State Superseded
Headers show
Series DRM: fix struct sg_table nents vs. orig_nents misuse | expand

Commit Message

Marek Szyprowski Aug. 26, 2020, 6:33 a.m. UTC 
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.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>

---
 drivers/gpu/drm/tegra/gem.c   | 27 ++++++++++-----------------
 drivers/gpu/drm/tegra/plane.c | 15 +++++----------
 2 files changed, 15 insertions(+), 27 deletions(-)

-- 
2.17.1

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Comments

Robin Murphy Sept. 1, 2020, 8:11 p.m. UTC | #1 
On 2020-08-26 07:33, Marek Szyprowski wrote:
> 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.


Reviewed-by: Robin Murphy <robin.murphy@arm.com>


> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>

> ---

>   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 723df142a981..01d94befab11 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, 0);

>   		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, 0);

> +	if (err)

>   		goto free_sgt;

> -	}

>   

>   	return 0;

>   

> @@ -571,7 +566,7 @@ tegra_gem_prime_map_dma_buf(struct dma_buf_attachment *attach,

>   			goto free;

>   	}

>   

> -	if (dma_map_sg(attach->dev, sgt->sgl, sgt->nents, dir) == 0)

> +	if (dma_map_sgtable(attach->dev, sgt, dir, 0))

>   		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, 0);

>   

>   	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 4cd0461cc508..539d14935728 100644

> --- a/drivers/gpu/drm/tegra/plane.c

> +++ b/drivers/gpu/drm/tegra/plane.c

> @@ -131,12 +131,9 @@ 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, 0);

> +			if (err)

>   				goto unpin;

> -			}

>   

>   			/*

>   			 * The display controller needs contiguous memory, so

> @@ -144,7 +141,7 @@ 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;

>   			}

> @@ -166,8 +163,7 @@ 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, 0);

>   

>   		host1x_bo_unpin(dc->dev, &bo->base, sgt);

>   		state->iova[i] = DMA_MAPPING_ERROR;

> @@ -186,8 +182,7 @@ 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, 0);

>   

>   		host1x_bo_unpin(dc->dev, &bo->base, sgt);

>   		state->iova[i] = DMA_MAPPING_ERROR;

> 

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diff mbox series

Patch

diff --git a/drivers/gpu/drm/tegra/gem.c b/drivers/gpu/drm/tegra/gem.c
index 723df142a981..01d94befab11 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, 0);
 		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, 0);
+	if (err)
 		goto free_sgt;
-	}
 
 	return 0;
 
@@ -571,7 +566,7 @@  tegra_gem_prime_map_dma_buf(struct dma_buf_attachment *attach,
 			goto free;
 	}
 
-	if (dma_map_sg(attach->dev, sgt->sgl, sgt->nents, dir) == 0)
+	if (dma_map_sgtable(attach->dev, sgt, dir, 0))
 		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, 0);
 
 	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 4cd0461cc508..539d14935728 100644
--- a/drivers/gpu/drm/tegra/plane.c
+++ b/drivers/gpu/drm/tegra/plane.c
@@ -131,12 +131,9 @@  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, 0);
+			if (err)
 				goto unpin;
-			}
 
 			/*
 			 * The display controller needs contiguous memory, so
@@ -144,7 +141,7 @@  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;
 			}
@@ -166,8 +163,7 @@  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, 0);
 
 		host1x_bo_unpin(dc->dev, &bo->base, sgt);
 		state->iova[i] = DMA_MAPPING_ERROR;
@@ -186,8 +182,7 @@  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, 0);
 
 		host1x_bo_unpin(dc->dev, &bo->base, sgt);
 		state->iova[i] = DMA_MAPPING_ERROR;