Commit d4fea3e6 authored by Marek Szyprowski's avatar Marek Szyprowski
Browse files

drm: tegra: fix common struct sg_table related issues 



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: default avatarMarek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: default avatarRobin Murphy <robin.murphy@arm.com>
parent 82c245b5

drivers/gpu/drm/tegra/gem.c

+10 −17
Original line number Diff line number Diff line
@@ -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;

}

drivers/gpu/drm/tegra/plane.c

+5 −10
Original line number Diff line number Diff line
@@ -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;