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Commit fa2845b2 authored by Marek Szyprowski's avatar Marek Szyprowski Committed by Greg Kroah-Hartman
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drm: etnaviv: fix common struct sg_table related issues 



[ Upstream commit 182354a526a0540c9197e03d9fce8a949ffd36ca ]

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>
Acked-by: default avatarLucas Stach <l.stach@pengutronix.de>
Stable-dep-of: d37c120b7312 ("drm/etnaviv: don't truncate physical page address")
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 4626550b

drivers/gpu/drm/etnaviv/etnaviv_gem.c

+5 −7
Original line number Diff line number Diff line
@@ -27,7 +27,7 @@ static void etnaviv_gem_scatter_map(struct etnaviv_gem_object *etnaviv_obj) 
	 * because display controller, GPU, etc. are not coherent.

	 */

	if (etnaviv_obj->flags & ETNA_BO_CACHE_MASK)

		dma_map_sg(dev->dev, sgt->sgl, sgt->nents, DMA_BIDIRECTIONAL);

		dma_map_sgtable(dev->dev, sgt, DMA_BIDIRECTIONAL, 0);

}



static void etnaviv_gem_scatterlist_unmap(struct etnaviv_gem_object *etnaviv_obj)
@@ -51,7 +51,7 @@ static void etnaviv_gem_scatterlist_unmap(struct etnaviv_gem_object *etnaviv_obj 
	 * discard those writes.

	 */

	if (etnaviv_obj->flags & ETNA_BO_CACHE_MASK)

		dma_unmap_sg(dev->dev, sgt->sgl, sgt->nents, DMA_BIDIRECTIONAL);

		dma_unmap_sgtable(dev->dev, sgt, DMA_BIDIRECTIONAL, 0);

}



/* called with etnaviv_obj->lock held */
@@ -403,8 +403,7 @@ int etnaviv_gem_cpu_prep(struct drm_gem_object *obj, u32 op, 
	}



	if (etnaviv_obj->flags & ETNA_BO_CACHED) {

		dma_sync_sg_for_cpu(dev->dev, etnaviv_obj->sgt->sgl,

				    etnaviv_obj->sgt->nents,

		dma_sync_sgtable_for_cpu(dev->dev, etnaviv_obj->sgt,

					 etnaviv_op_to_dma_dir(op));

		etnaviv_obj->last_cpu_prep_op = op;

	}
@@ -420,8 +419,7 @@ int etnaviv_gem_cpu_fini(struct drm_gem_object *obj) 
	if (etnaviv_obj->flags & ETNA_BO_CACHED) {

		/* fini without a prep is almost certainly a userspace error */

		WARN_ON(etnaviv_obj->last_cpu_prep_op == 0);

		dma_sync_sg_for_device(dev->dev, etnaviv_obj->sgt->sgl,

			etnaviv_obj->sgt->nents,

		dma_sync_sgtable_for_device(dev->dev, etnaviv_obj->sgt,

			etnaviv_op_to_dma_dir(etnaviv_obj->last_cpu_prep_op));

		etnaviv_obj->last_cpu_prep_op = 0;

	}

drivers/gpu/drm/etnaviv/etnaviv_mmu.c

+4 −11
Original line number Diff line number Diff line
@@ -73,13 +73,13 @@ static int etnaviv_iommu_map(struct etnaviv_iommu_context *context, u32 iova, 
			     struct sg_table *sgt, unsigned len, int prot)

{	struct scatterlist *sg;

	unsigned int da = iova;

	unsigned int i, j;

	unsigned int i;

	int ret;



	if (!context || !sgt)

		return -EINVAL;



	for_each_sg(sgt->sgl, sg, sgt->nents, i) {

	for_each_sgtable_dma_sg(sgt, sg, i) {

		u32 pa = sg_dma_address(sg) - sg->offset;

		size_t bytes = sg_dma_len(sg) + sg->offset;
@@ -95,14 +95,7 @@ static int etnaviv_iommu_map(struct etnaviv_iommu_context *context, u32 iova, 
	return 0;



fail:

	da = iova;



	for_each_sg(sgt->sgl, sg, i, j) {

		size_t bytes = sg_dma_len(sg) + sg->offset;



		etnaviv_context_unmap(context, da, bytes);

		da += bytes;

	}

	etnaviv_context_unmap(context, iova, da - iova);

	return ret;

}
@@ -113,7 +106,7 @@ static void etnaviv_iommu_unmap(struct etnaviv_iommu_context *context, u32 iova, 
	unsigned int da = iova;

	int i;



	for_each_sg(sgt->sgl, sg, sgt->nents, i) {

	for_each_sgtable_dma_sg(sgt, sg, i) {

		size_t bytes = sg_dma_len(sg) + sg->offset;



		etnaviv_context_unmap(context, da, bytes);