[PATCH v7 20/36] drm: tegra: fix common struct sg_table related issues

[PATCH v7 20/36] drm: tegra: fix common struct sg_table related issues

[Marek Szyprowski]

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-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
---
 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 9ccfb56e9b01..0d2ef1662a39 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, 0);
+			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, 0);
 
 		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, 0);
 
 		host1x_bo_unpin(dc->dev, &bo->base, sgt);
 		state->iova[i] = DMA_MAPPING_ERROR;
-- 
2.17.1

[PATCH v7 26/36] drm: host1x: fix common struct sg_table related issues

[Marek Szyprowski]

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-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
---
 drivers/gpu/host1x/job.c | 22 ++++++++--------------
 1 file changed, 8 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/host1x/job.c b/drivers/gpu/host1x/job.c
index a10643aa89aa..4832b57f10c4 100644
--- a/drivers/gpu/host1x/job.c
+++ b/drivers/gpu/host1x/job.c
@@ -166,11 +166,9 @@ static unsigned int pin_job(struct host1x *host, struct host1x_job *job)
 				goto unpin;
 			}
 
-			err = dma_map_sg(dev, sgt->sgl, sgt->nents, dir);
-			if (!err) {
-				err = -ENOMEM;
+			err = dma_map_sgtable(dev, sgt, dir, 0);
+			if (err)
 				goto unpin;
-			}
 
 			job->unpins[job->num_unpins].dev = dev;
 			job->unpins[job->num_unpins].dir = dir;
@@ -217,7 +215,7 @@ static unsigned int pin_job(struct host1x *host, struct host1x_job *job)
 		}
 
 		if (!IS_ENABLED(CONFIG_TEGRA_HOST1X_FIREWALL) && host->domain) {
-			for_each_sg(sgt->sgl, sg, sgt->nents, j)
+			for_each_sgtable_sg(sgt, sg, j)
 				gather_size += sg->length;
 			gather_size = iova_align(&host->iova, gather_size);
 
@@ -229,9 +227,9 @@ static unsigned int pin_job(struct host1x *host, struct host1x_job *job)
 				goto unpin;
 			}
 
-			err = iommu_map_sg(host->domain,
+			err = iommu_map_sgtable(host->domain,
 					iova_dma_addr(&host->iova, alloc),
-					sgt->sgl, sgt->nents, IOMMU_READ);
+					sgt, IOMMU_READ);
 			if (err == 0) {
 				__free_iova(&host->iova, alloc);
 				err = -EINVAL;
@@ -241,12 +239,9 @@ static unsigned int pin_job(struct host1x *host, struct host1x_job *job)
 			job->unpins[job->num_unpins].size = gather_size;
 			phys_addr = iova_dma_addr(&host->iova, alloc);
 		} else if (sgt) {
-			err = dma_map_sg(host->dev, sgt->sgl, sgt->nents,
-					 DMA_TO_DEVICE);
-			if (!err) {
-				err = -ENOMEM;
+			err = dma_map_sgtable(host->dev, sgt, DMA_TO_DEVICE, 0);
+			if (err)
 				goto unpin;
-			}
 
 			job->unpins[job->num_unpins].dir = DMA_TO_DEVICE;
 			job->unpins[job->num_unpins].dev = host->dev;
@@ -647,8 +642,7 @@ void host1x_job_unpin(struct host1x_job *job)
 		}
 
 		if (unpin->dev && sgt)
-			dma_unmap_sg(unpin->dev, sgt->sgl, sgt->nents,
-				     unpin->dir);
+			dma_unmap_sgtable(unpin->dev, sgt, unpin->dir, 0);
 
 		host1x_bo_unpin(dev, unpin->bo, sgt);
 		host1x_bo_put(unpin->bo);
-- 
2.17.1

Re: [PATCH v7 26/36] drm: host1x: fix common struct sg_table related issues

[kernel test robot]

[-- Attachment #1: Type: text/plain, Size: 7211 bytes --]

Hi Marek,

I love your patch! Yet something to improve:

[auto build test ERROR on next-20200618]
[also build test ERROR on v5.8-rc1]
[cannot apply to linuxtv-media/master staging/staging-testing drm-exynos/exynos-drm-next drm-intel/for-linux-next linus/master v5.8-rc1 v5.7 v5.7-rc7]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use  as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Marek-Szyprowski/DRM-fix-struct-sg_table-nents-vs-orig_nents-misuse/20200619-184302
base:    ce2cc8efd7a40cbd17841add878cb691d0ce0bba
config: arm64-randconfig-r036-20200621 (attached as .config)
compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project ef455a55bcf2cfea04a99c361b182ad18b7f03f1)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install arm64 cross compiling tool for clang build
        # apt-get install binutils-aarch64-linux-gnu
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=arm64 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>

All errors (new ones prefixed by >>):

>> drivers/gpu/host1x/job.c:230:10: error: implicit declaration of function 'iommu_map_sgtable' [-Werror,-Wimplicit-function-declaration]
                           err = iommu_map_sgtable(host->domain,
                                 ^
   drivers/gpu/host1x/job.c:230:10: note: did you mean 'dma_map_sgtable'?
   include/linux/dma-mapping.h:628:19: note: 'dma_map_sgtable' declared here
   static inline int dma_map_sgtable(struct device *dev, struct sg_table *sgt,
                     ^
   1 error generated.

vim +/iommu_map_sgtable +230 drivers/gpu/host1x/job.c

   100	
   101	static unsigned int pin_job(struct host1x *host, struct host1x_job *job)
   102	{
   103		struct host1x_client *client = job->client;
   104		struct device *dev = client->dev;
   105		struct iommu_domain *domain;
   106		unsigned int i;
   107		int err;
   108	
   109		domain = iommu_get_domain_for_dev(dev);
   110		job->num_unpins = 0;
   111	
   112		for (i = 0; i < job->num_relocs; i++) {
   113			struct host1x_reloc *reloc = &job->relocs[i];
   114			dma_addr_t phys_addr, *phys;
   115			struct sg_table *sgt;
   116	
   117			reloc->target.bo = host1x_bo_get(reloc->target.bo);
   118			if (!reloc->target.bo) {
   119				err = -EINVAL;
   120				goto unpin;
   121			}
   122	
   123			/*
   124			 * If the client device is not attached to an IOMMU, the
   125			 * physical address of the buffer object can be used.
   126			 *
   127			 * Similarly, when an IOMMU domain is shared between all
   128			 * host1x clients, the IOVA is already available, so no
   129			 * need to map the buffer object again.
   130			 *
   131			 * XXX Note that this isn't always safe to do because it
   132			 * relies on an assumption that no cache maintenance is
   133			 * needed on the buffer objects.
   134			 */
   135			if (!domain || client->group)
   136				phys = &phys_addr;
   137			else
   138				phys = NULL;
   139	
   140			sgt = host1x_bo_pin(dev, reloc->target.bo, phys);
   141			if (IS_ERR(sgt)) {
   142				err = PTR_ERR(sgt);
   143				goto unpin;
   144			}
   145	
   146			if (sgt) {
   147				unsigned long mask = HOST1X_RELOC_READ |
   148						     HOST1X_RELOC_WRITE;
   149				enum dma_data_direction dir;
   150	
   151				switch (reloc->flags & mask) {
   152				case HOST1X_RELOC_READ:
   153					dir = DMA_TO_DEVICE;
   154					break;
   155	
   156				case HOST1X_RELOC_WRITE:
   157					dir = DMA_FROM_DEVICE;
   158					break;
   159	
   160				case HOST1X_RELOC_READ | HOST1X_RELOC_WRITE:
   161					dir = DMA_BIDIRECTIONAL;
   162					break;
   163	
   164				default:
   165					err = -EINVAL;
   166					goto unpin;
   167				}
   168	
   169				err = dma_map_sgtable(dev, sgt, dir, 0);
   170				if (err)
   171					goto unpin;
   172	
   173				job->unpins[job->num_unpins].dev = dev;
   174				job->unpins[job->num_unpins].dir = dir;
   175				phys_addr = sg_dma_address(sgt->sgl);
   176			}
   177	
   178			job->addr_phys[job->num_unpins] = phys_addr;
   179			job->unpins[job->num_unpins].bo = reloc->target.bo;
   180			job->unpins[job->num_unpins].sgt = sgt;
   181			job->num_unpins++;
   182		}
   183	
   184		for (i = 0; i < job->num_gathers; i++) {
   185			struct host1x_job_gather *g = &job->gathers[i];
   186			size_t gather_size = 0;
   187			struct scatterlist *sg;
   188			struct sg_table *sgt;
   189			dma_addr_t phys_addr;
   190			unsigned long shift;
   191			struct iova *alloc;
   192			dma_addr_t *phys;
   193			unsigned int j;
   194	
   195			g->bo = host1x_bo_get(g->bo);
   196			if (!g->bo) {
   197				err = -EINVAL;
   198				goto unpin;
   199			}
   200	
   201			/**
   202			 * If the host1x is not attached to an IOMMU, there is no need
   203			 * to map the buffer object for the host1x, since the physical
   204			 * address can simply be used.
   205			 */
   206			if (!iommu_get_domain_for_dev(host->dev))
   207				phys = &phys_addr;
   208			else
   209				phys = NULL;
   210	
   211			sgt = host1x_bo_pin(host->dev, g->bo, phys);
   212			if (IS_ERR(sgt)) {
   213				err = PTR_ERR(sgt);
   214				goto unpin;
   215			}
   216	
   217			if (!IS_ENABLED(CONFIG_TEGRA_HOST1X_FIREWALL) && host->domain) {
   218				for_each_sgtable_sg(sgt, sg, j)
   219					gather_size += sg->length;
   220				gather_size = iova_align(&host->iova, gather_size);
   221	
   222				shift = iova_shift(&host->iova);
   223				alloc = alloc_iova(&host->iova, gather_size >> shift,
   224						   host->iova_end >> shift, true);
   225				if (!alloc) {
   226					err = -ENOMEM;
   227					goto unpin;
   228				}
   229	
 > 230				err = iommu_map_sgtable(host->domain,
   231						iova_dma_addr(&host->iova, alloc),
   232						sgt, IOMMU_READ);
   233				if (err == 0) {
   234					__free_iova(&host->iova, alloc);
   235					err = -EINVAL;
   236					goto unpin;
   237				}
   238	
   239				job->unpins[job->num_unpins].size = gather_size;
   240				phys_addr = iova_dma_addr(&host->iova, alloc);
   241			} else if (sgt) {
   242				err = dma_map_sgtable(host->dev, sgt, DMA_TO_DEVICE, 0);
   243				if (err)
   244					goto unpin;
   245	
   246				job->unpins[job->num_unpins].dir = DMA_TO_DEVICE;
   247				job->unpins[job->num_unpins].dev = host->dev;
   248				phys_addr = sg_dma_address(sgt->sgl);
   249			}
   250	
   251			job->addr_phys[job->num_unpins] = phys_addr;
   252			job->gather_addr_phys[i] = phys_addr;
   253	
   254			job->unpins[job->num_unpins].bo = g->bo;
   255			job->unpins[job->num_unpins].sgt = sgt;
   256			job->num_unpins++;
   257		}
   258	
   259		return 0;
   260	
   261	unpin:
   262		host1x_job_unpin(job);
   263		return err;
   264	}
   265	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org

[-- Attachment #2: .config.gz --]
[-- Type: application/gzip, Size: 35472 bytes --]

[-- Attachment #3: Type: text/plain, Size: 0 bytes --]

[PATCH v7 31/36] staging: tegra-vde: fix common struct sg_table related issues

[Marek Szyprowski]

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-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
Reviewed-by: Dmitry Osipenko <digetx-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
---
 drivers/staging/media/tegra-vde/iommu.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/media/tegra-vde/iommu.c b/drivers/staging/media/tegra-vde/iommu.c
index 6af863d92123..adf8dc7ee25c 100644
--- a/drivers/staging/media/tegra-vde/iommu.c
+++ b/drivers/staging/media/tegra-vde/iommu.c
@@ -36,8 +36,8 @@ int tegra_vde_iommu_map(struct tegra_vde *vde,
 
 	addr = iova_dma_addr(&vde->iova, iova);
 
-	size = iommu_map_sg(vde->domain, addr, sgt->sgl, sgt->nents,
-			    IOMMU_READ | IOMMU_WRITE);
+	size = iommu_map_sgtable(vde->domain, addr, sgt,
+				 IOMMU_READ | IOMMU_WRITE);
 	if (!size) {
 		__free_iova(&vde->iova, iova);
 		return -ENXIO;
-- 
2.17.1

Re: [PATCH v7 31/36] staging: tegra-vde: fix common struct sg_table related issues

[Dmitry Osipenko]

В Fri, 19 Jun 2020 12:36:31 +0200
Marek Szyprowski <m.szyprowski@samsung.com> пишет:

> 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: Dmitry Osipenko <digetx@gmail.com>
> ---
>  drivers/staging/media/tegra-vde/iommu.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/media/tegra-vde/iommu.c
> b/drivers/staging/media/tegra-vde/iommu.c index
> 6af863d92123..adf8dc7ee25c 100644 ---
> a/drivers/staging/media/tegra-vde/iommu.c +++
> b/drivers/staging/media/tegra-vde/iommu.c @@ -36,8 +36,8 @@ int
> tegra_vde_iommu_map(struct tegra_vde *vde, 
>  	addr = iova_dma_addr(&vde->iova, iova);
>  
> -	size = iommu_map_sg(vde->domain, addr, sgt->sgl, sgt->nents,
> -			    IOMMU_READ | IOMMU_WRITE);
> +	size = iommu_map_sgtable(vde->domain, addr, sgt,
> +				 IOMMU_READ | IOMMU_WRITE);
>  	if (!size) {
>  		__free_iova(&vde->iova, iova);
>  		return -ENXIO;

Ahh, I saw the build failure report. You're changing the DMA API in
this series, while DMA API isn't used by this driver, it uses IOMMU
API. Hence there is no need to touch this code. Similar problem in the
host1x driver patch.
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Re: [PATCH v7 31/36] staging: tegra-vde: fix common struct sg_table related issues

[Marek Szyprowski]

On 21.06.2020 06:00, Dmitry Osipenko wrote:
> В Fri, 19 Jun 2020 12:36:31 +0200
> Marek Szyprowski <m.szyprowski@samsung.com> пишет:
>
>> 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: Dmitry Osipenko <digetx@gmail.com>
>> ---
>>   drivers/staging/media/tegra-vde/iommu.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/staging/media/tegra-vde/iommu.c
>> b/drivers/staging/media/tegra-vde/iommu.c index
>> 6af863d92123..adf8dc7ee25c 100644 ---
>> a/drivers/staging/media/tegra-vde/iommu.c +++
>> b/drivers/staging/media/tegra-vde/iommu.c @@ -36,8 +36,8 @@ int
>> tegra_vde_iommu_map(struct tegra_vde *vde,
>>   	addr = iova_dma_addr(&vde->iova, iova);
>>   
>> -	size = iommu_map_sg(vde->domain, addr, sgt->sgl, sgt->nents,
>> -			    IOMMU_READ | IOMMU_WRITE);
>> +	size = iommu_map_sgtable(vde->domain, addr, sgt,
>> +				 IOMMU_READ | IOMMU_WRITE);
>>   	if (!size) {
>>   		__free_iova(&vde->iova, iova);
>>   		return -ENXIO;
> Ahh, I saw the build failure report. You're changing the DMA API in
> this series, while DMA API isn't used by this driver, it uses IOMMU
> API. Hence there is no need to touch this code. Similar problem in the
> host1x driver patch.

The issue is caused by the lack of iommu_map_sgtable() stub when no 
IOMMU support is configured. I've posted a patch for this:

https://lore.kernel.org/lkml/20200630081756.18526-1-m.szyprowski@samsung.com/

The patch for this driver is fine, we have to wait until the above fix 
gets merged and then it can be applied during the next release cycle.

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland

Re: [PATCH v7 31/36] staging: tegra-vde: fix common struct sg_table related issues

[Dmitry Osipenko]

30.06.2020 13:07, Marek Szyprowski пишет:
> On 21.06.2020 06:00, Dmitry Osipenko wrote:
>> В Fri, 19 Jun 2020 12:36:31 +0200
>> Marek Szyprowski <m.szyprowski@samsung.com> пишет:
>>
>>> 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: Dmitry Osipenko <digetx@gmail.com>
>>> ---
>>>   drivers/staging/media/tegra-vde/iommu.c | 4 ++--
>>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/staging/media/tegra-vde/iommu.c
>>> b/drivers/staging/media/tegra-vde/iommu.c index
>>> 6af863d92123..adf8dc7ee25c 100644 ---
>>> a/drivers/staging/media/tegra-vde/iommu.c +++
>>> b/drivers/staging/media/tegra-vde/iommu.c @@ -36,8 +36,8 @@ int
>>> tegra_vde_iommu_map(struct tegra_vde *vde,
>>>   	addr = iova_dma_addr(&vde->iova, iova);
>>>   
>>> -	size = iommu_map_sg(vde->domain, addr, sgt->sgl, sgt->nents,
>>> -			    IOMMU_READ | IOMMU_WRITE);
>>> +	size = iommu_map_sgtable(vde->domain, addr, sgt,
>>> +				 IOMMU_READ | IOMMU_WRITE);
>>>   	if (!size) {
>>>   		__free_iova(&vde->iova, iova);
>>>   		return -ENXIO;
>> Ahh, I saw the build failure report. You're changing the DMA API in
>> this series, while DMA API isn't used by this driver, it uses IOMMU
>> API. Hence there is no need to touch this code. Similar problem in the
>> host1x driver patch.
> 
> The issue is caused by the lack of iommu_map_sgtable() stub when no 
> IOMMU support is configured. I've posted a patch for this:
> 
> https://lore.kernel.org/lkml/20200630081756.18526-1-m.szyprowski@samsung.com/
> 
> The patch for this driver is fine, we have to wait until the above fix 
> gets merged and then it can be applied during the next release cycle.

Thank you for the clarification!
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