diff mbox series

[v10,05/30] drm: etnaviv: fix common struct sg_table related issues

Message ID 20200904131711.12950-6-m.szyprowski@samsung.com
State Accepted
Commit 182354a526a0540c9197e03d9fce8a949ffd36ca
Headers show
Series DRM: fix struct sg_table nents vs. orig_nents misuse | expand

Commit Message

Marek Szyprowski Sept. 4, 2020, 1:16 p.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>

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

---
 drivers/gpu/drm/etnaviv/etnaviv_gem.c | 12 +++++-------
 drivers/gpu/drm/etnaviv/etnaviv_mmu.c | 15 ++++-----------
 2 files changed, 9 insertions(+), 18 deletions(-)

-- 
2.17.1

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Comments

Lucas Stach Sept. 4, 2020, 1:37 p.m. UTC | #1
On Fr, 2020-09-04 at 15:16 +0200, 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.

> 

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

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


Acked-by: Lucas Stach <l.stach@pengutronix.de>


> ---

>  drivers/gpu/drm/etnaviv/etnaviv_gem.c | 12 +++++-------

>  drivers/gpu/drm/etnaviv/etnaviv_mmu.c | 15 ++++-----------

>  2 files changed, 9 insertions(+), 18 deletions(-)

> 

> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gem.c b/drivers/gpu/drm/etnaviv/etnaviv_gem.c

> index f06e19e7be04..eaf1949bc2e4 100644

> --- a/drivers/gpu/drm/etnaviv/etnaviv_gem.c

> +++ b/drivers/gpu/drm/etnaviv/etnaviv_gem.c

> @@ -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 */

> @@ -404,9 +404,8 @@ 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,

> -				    etnaviv_op_to_dma_dir(op));

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

> +					 etnaviv_op_to_dma_dir(op));

>  		etnaviv_obj->last_cpu_prep_op = op;

>  	}

>  

> @@ -421,8 +420,7 @@ 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;

>  	}

> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_mmu.c b/drivers/gpu/drm/etnaviv/etnaviv_mmu.c

> index 3607d348c298..15d9fa3879e5 100644

> --- a/drivers/gpu/drm/etnaviv/etnaviv_mmu.c

> +++ b/drivers/gpu/drm/etnaviv/etnaviv_mmu.c

> @@ -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);


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diff mbox series

Patch

diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gem.c b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
index f06e19e7be04..eaf1949bc2e4 100644
--- a/drivers/gpu/drm/etnaviv/etnaviv_gem.c
+++ b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
@@ -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 */
@@ -404,9 +404,8 @@  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,
-				    etnaviv_op_to_dma_dir(op));
+		dma_sync_sgtable_for_cpu(dev->dev, etnaviv_obj->sgt,
+					 etnaviv_op_to_dma_dir(op));
 		etnaviv_obj->last_cpu_prep_op = op;
 	}
 
@@ -421,8 +420,7 @@  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;
 	}
diff --git a/drivers/gpu/drm/etnaviv/etnaviv_mmu.c b/drivers/gpu/drm/etnaviv/etnaviv_mmu.c
index 3607d348c298..15d9fa3879e5 100644
--- a/drivers/gpu/drm/etnaviv/etnaviv_mmu.c
+++ b/drivers/gpu/drm/etnaviv/etnaviv_mmu.c
@@ -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);