fix a layering violation in videobuf2 and improve dma_map_resource v2

fix a layering violation in videobuf2 and improve dma_map_resource v2

[Christoph Hellwig]

Hi all,

this series fixes a rather gross layering violation in videobuf2, which
pokes into arm DMA mapping internals to get a DMA address for memory that
does not have a page structure, and to do so fixes up the dma_map_resource
implementation to not provide a somewhat dangerous default and improve
the error handling.

Changes since v1:
 - don't apply bus offsets in dma_direct_map_resource

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[PATCH 1/3] dma-mapping: remove the default map_resource implementation

[Christoph Hellwig]

Instead provide a proper implementation in the direct mapping code, and
also wire it up for arm and powerpc, leaving an error return for all the
IOMMU or virtual mapping instances for which we'd have to wire up an
actual implementation

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/arm/mm/dma-mapping.c         |  2 ++
 arch/powerpc/kernel/dma-swiotlb.c |  1 +
 arch/powerpc/kernel/dma.c         |  1 +
 include/linux/dma-mapping.h       | 12 +++++++-----
 kernel/dma/direct.c               | 14 ++++++++++++++
 5 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index f1e2922e447c..3c8534904209 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -188,6 +188,7 @@ const struct dma_map_ops arm_dma_ops = {
 	.unmap_page		= arm_dma_unmap_page,
 	.map_sg			= arm_dma_map_sg,
 	.unmap_sg		= arm_dma_unmap_sg,
+	.map_resource		= dma_direct_map_resource,
 	.sync_single_for_cpu	= arm_dma_sync_single_for_cpu,
 	.sync_single_for_device	= arm_dma_sync_single_for_device,
 	.sync_sg_for_cpu	= arm_dma_sync_sg_for_cpu,
@@ -211,6 +212,7 @@ const struct dma_map_ops arm_coherent_dma_ops = {
 	.get_sgtable		= arm_dma_get_sgtable,
 	.map_page		= arm_coherent_dma_map_page,
 	.map_sg			= arm_dma_map_sg,
+	.map_resource		= dma_direct_map_resource,
 	.dma_supported		= arm_dma_supported,
 };
 EXPORT_SYMBOL(arm_coherent_dma_ops);
diff --git a/arch/powerpc/kernel/dma-swiotlb.c b/arch/powerpc/kernel/dma-swiotlb.c
index 7d5fc9751622..fbb2506a414e 100644
--- a/arch/powerpc/kernel/dma-swiotlb.c
+++ b/arch/powerpc/kernel/dma-swiotlb.c
@@ -55,6 +55,7 @@ const struct dma_map_ops powerpc_swiotlb_dma_ops = {
 	.dma_supported = swiotlb_dma_supported,
 	.map_page = dma_direct_map_page,
 	.unmap_page = dma_direct_unmap_page,
+	.map_resource = dma_direct_map_resource,
 	.sync_single_for_cpu = dma_direct_sync_single_for_cpu,
 	.sync_single_for_device = dma_direct_sync_single_for_device,
 	.sync_sg_for_cpu = dma_direct_sync_sg_for_cpu,
diff --git a/arch/powerpc/kernel/dma.c b/arch/powerpc/kernel/dma.c
index b1903ebb2e9c..258b9e8ebb99 100644
--- a/arch/powerpc/kernel/dma.c
+++ b/arch/powerpc/kernel/dma.c
@@ -273,6 +273,7 @@ const struct dma_map_ops dma_nommu_ops = {
 	.dma_supported			= dma_nommu_dma_supported,
 	.map_page			= dma_nommu_map_page,
 	.unmap_page			= dma_nommu_unmap_page,
+	.map_resource			= dma_direct_map_resource,
 	.get_required_mask		= dma_nommu_get_required_mask,
 #ifdef CONFIG_NOT_COHERENT_CACHE
 	.sync_single_for_cpu 		= dma_nommu_sync_single,
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index f6ded992c183..9842085e6774 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -208,6 +208,8 @@ dma_addr_t dma_direct_map_page(struct device *dev, struct page *page,
 		unsigned long attrs);
 int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, int nents,
 		enum dma_data_direction dir, unsigned long attrs);
+dma_addr_t dma_direct_map_resource(struct device *dev, phys_addr_t paddr,
+		size_t size, enum dma_data_direction dir, unsigned long attrs);
 
 #if defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_DEVICE) || \
     defined(CONFIG_SWIOTLB)
@@ -346,19 +348,19 @@ static inline dma_addr_t dma_map_resource(struct device *dev,
 					  unsigned long attrs)
 {
 	const struct dma_map_ops *ops = get_dma_ops(dev);
-	dma_addr_t addr;
+	dma_addr_t addr = DMA_MAPPING_ERROR;
 
 	BUG_ON(!valid_dma_direction(dir));
 
 	/* Don't allow RAM to be mapped */
 	BUG_ON(pfn_valid(PHYS_PFN(phys_addr)));
 
-	addr = phys_addr;
-	if (ops && ops->map_resource)
+	if (dma_is_direct(ops))
+		addr = dma_direct_map_resource(dev, phys_addr, size, dir, attrs);
+	else if (ops->map_resource)
 		addr = ops->map_resource(dev, phys_addr, size, dir, attrs);
 
 	debug_dma_map_resource(dev, phys_addr, size, dir, addr);
-
 	return addr;
 }
 
@@ -369,7 +371,7 @@ static inline void dma_unmap_resource(struct device *dev, dma_addr_t addr,
 	const struct dma_map_ops *ops = get_dma_ops(dev);
 
 	BUG_ON(!valid_dma_direction(dir));
-	if (ops && ops->unmap_resource)
+	if (!dma_is_direct(ops) && ops->unmap_resource)
 		ops->unmap_resource(dev, addr, size, dir, attrs);
 	debug_dma_unmap_resource(dev, addr, size, dir);
 }
diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 355d16acee6d..25bd19974223 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -356,6 +356,20 @@ int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, int nents,
 }
 EXPORT_SYMBOL(dma_direct_map_sg);
 
+dma_addr_t dma_direct_map_resource(struct device *dev, phys_addr_t paddr,
+		size_t size, enum dma_data_direction dir, unsigned long attrs)
+{
+	dma_addr_t dma_addr = paddr;
+
+	if (unlikely(!dma_direct_possible(dev, dma_addr, size))) {
+		report_addr(dev, dma_addr, size);
+		return DMA_MAPPING_ERROR;
+	}
+
+	return dma_addr;
+}
+EXPORT_SYMBOL(dma_direct_map_resource);
+
 /*
  * Because 32-bit DMA masks are so common we expect every architecture to be
  * able to satisfy them - either by not supporting more physical memory, or by
-- 
2.20.1


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[PATCH 2/3] dma-mapping: don't BUG when calling dma_map_resource on RAM

[Christoph Hellwig]

Use WARN_ON_ONCE to print a stack trace and return a proper error
code instead.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
---
 include/linux/dma-mapping.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 9842085e6774..b904d55247ab 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -353,7 +353,8 @@ static inline dma_addr_t dma_map_resource(struct device *dev,
 	BUG_ON(!valid_dma_direction(dir));
 
 	/* Don't allow RAM to be mapped */
-	BUG_ON(pfn_valid(PHYS_PFN(phys_addr)));
+	if (WARN_ON_ONCE(pfn_valid(PHYS_PFN(phys_addr))))
+		return DMA_MAPPING_ERROR;
 
 	if (dma_is_direct(ops))
 		addr = dma_direct_map_resource(dev, phys_addr, size, dir, attrs);
-- 
2.20.1


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[PATCH 3/3] videobuf2: replace a layering violation with dma_map_resource

[Christoph Hellwig]

vb2_dc_get_userptr pokes into arm direct mapping details to get the
resemblance of a dma address for a a physical address that does is
not backed by a page struct.  Not only is this not portable to other
architectures with dma direct mapping offsets, but also not to uses
of IOMMUs of any kind.  Switch to the proper dma_map_resource /
dma_unmap_resource interface instead.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
---
 .../common/videobuf2/videobuf2-dma-contig.c   | 41 ++++---------------
 1 file changed, 9 insertions(+), 32 deletions(-)

diff --git a/drivers/media/common/videobuf2/videobuf2-dma-contig.c b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
index aff0ab7bf83d..82389aead6ed 100644
--- a/drivers/media/common/videobuf2/videobuf2-dma-contig.c
+++ b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
@@ -439,42 +439,14 @@ static void vb2_dc_put_userptr(void *buf_priv)
 				set_page_dirty_lock(pages[i]);
 		sg_free_table(sgt);
 		kfree(sgt);
+	} else {
+		dma_unmap_resource(buf->dev, buf->dma_addr, buf->size,
+				   buf->dma_dir, 0);
 	}
 	vb2_destroy_framevec(buf->vec);
 	kfree(buf);
 }
 
-/*
- * For some kind of reserved memory there might be no struct page available,
- * so all that can be done to support such 'pages' is to try to convert
- * pfn to dma address or at the last resort just assume that
- * dma address == physical address (like it has been assumed in earlier version
- * of videobuf2-dma-contig
- */
-
-#ifdef __arch_pfn_to_dma
-static inline dma_addr_t vb2_dc_pfn_to_dma(struct device *dev, unsigned long pfn)
-{
-	return (dma_addr_t)__arch_pfn_to_dma(dev, pfn);
-}
-#elif defined(__pfn_to_bus)
-static inline dma_addr_t vb2_dc_pfn_to_dma(struct device *dev, unsigned long pfn)
-{
-	return (dma_addr_t)__pfn_to_bus(pfn);
-}
-#elif defined(__pfn_to_phys)
-static inline dma_addr_t vb2_dc_pfn_to_dma(struct device *dev, unsigned long pfn)
-{
-	return (dma_addr_t)__pfn_to_phys(pfn);
-}
-#else
-static inline dma_addr_t vb2_dc_pfn_to_dma(struct device *dev, unsigned long pfn)
-{
-	/* really, we cannot do anything better at this point */
-	return (dma_addr_t)(pfn) << PAGE_SHIFT;
-}
-#endif
-
 static void *vb2_dc_get_userptr(struct device *dev, unsigned long vaddr,
 	unsigned long size, enum dma_data_direction dma_dir)
 {
@@ -528,7 +500,12 @@ static void *vb2_dc_get_userptr(struct device *dev, unsigned long vaddr,
 		for (i = 1; i < n_pages; i++)
 			if (nums[i-1] + 1 != nums[i])
 				goto fail_pfnvec;
-		buf->dma_addr = vb2_dc_pfn_to_dma(buf->dev, nums[0]);
+		buf->dma_addr = dma_map_resource(buf->dev,
+				__pfn_to_phys(nums[0]), size, buf->dma_dir, 0);
+		if (dma_mapping_error(buf->dev, buf->dma_addr)) {
+			ret = -ENOMEM;
+			goto fail_pfnvec;
+		}
 		goto out;
 	}
 
-- 
2.20.1


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Re: fix a layering violation in videobuf2 and improve dma_map_resource v2

[Marek Szyprowski]

Hi All,

On 2019-01-18 12:37, Christoph Hellwig wrote:
> Hi all,
>
> this series fixes a rather gross layering violation in videobuf2, which
> pokes into arm DMA mapping internals to get a DMA address for memory that
> does not have a page structure, and to do so fixes up the dma_map_resource
> implementation to not provide a somewhat dangerous default and improve
> the error handling.
>
> Changes since v1:
>  - don't apply bus offsets in dma_direct_map_resource

Works fine on older Exynos based boards with IOMMU and CMA disabled.

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

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


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Re: fix a layering violation in videobuf2 and improve dma_map_resource v2

[Christoph Hellwig]

On Fri, Feb 01, 2019 at 08:05:21AM +0100, Marek Szyprowski wrote:
> Works fine on older Exynos based boards with IOMMU and CMA disabled.
> 
> Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>

Thanks.  I've merged the ѕeries into the dma-mapping tree, and I've
also made a stable branch available at:

    git://git.infradead.org/users/hch/dma-mapping.git videobuf-map-resource

in case it needs to be pulled into the media tree.

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Re: [PATCH 3/3] videobuf2: replace a layering violation with dma_map_resource

[Christoph Hellwig]

Hi Marek,

can chance you could retest the v2 version?

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Re: [PATCH 3/3] videobuf2: replace a layering violation with dma_map_resource

[Marek Szyprowski]

Hi Christoph,

On 2019-01-17 18:21, Christoph Hellwig wrote:
> On Mon, Jan 14, 2019 at 01:42:26PM +0100, Marek Szyprowski wrote:
>> On 2019-01-11 19:17, Christoph Hellwig wrote:
>>> vb2_dc_get_userptr pokes into arm direct mapping details to get the
>>> resemblance of a dma address for a a physical address that does is
>>> not backed by a page struct.  Not only is this not portable to other
>>> architectures with dma direct mapping offsets, but also not to uses
>>> of IOMMUs of any kind.  Switch to the proper dma_map_resource /
>>> dma_unmap_resource interface instead.
>>>
>>> Signed-off-by: Christoph Hellwig <hch@lst.de>
>> There are checks for IOMMU presence in other places in vb2-dma-contig,
>> so it was used only when no IOMMU is available, but I agree that the
>> hacky code should be replaced by a generic code if possible.
>>
>> Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
>>
>> V4L2 pipeline works fine on older Exynos-based boards with CMA and IOMMU
>> disabled.
> Do you know if these rely on the offsets?  E.g. would they still work
> with the patch below applied on top.  That would keep the map_resource
> semantics as-is as solve the issue pointed out by Robin for now.

AFAIK that code was only used for sharing buffers between hardware
modules that are a part of the same SoC, usually implemented as platform
devices. AFAIR this never worked for devices on different buses. So far
I wasn't aware on ANY which would require an offset for the DMA access.

The first version of videobuf2-dc code even incorrectly used paddr
instead of dma_addr as a buffer 'address' returned to the client
drivers, because in case of those SoC this was exactly the same (see
commits 472af2b05bdefcaee7e754e22cbf131110017ad6 and
ba7fcb0c954921534707f08ebc4d8beeb2eb17e7).

> If not I can only think of a flag to bypass the offseting for now, but
> that would be pretty ugly.  Or go for the long-term solution of
> discovering the relationship between the two devices, as done by the
> PCIe P2P code..
>
> diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
> index 8e0359b04957..25bd19974223 100644
> --- a/kernel/dma/direct.c
> +++ b/kernel/dma/direct.c
> @@ -359,7 +359,7 @@ EXPORT_SYMBOL(dma_direct_map_sg);
>  dma_addr_t dma_direct_map_resource(struct device *dev, phys_addr_t paddr,
>  		size_t size, enum dma_data_direction dir, unsigned long attrs)
>  {
> -	dma_addr_t dma_addr = phys_to_dma(dev, paddr);
> +	dma_addr_t dma_addr = paddr;
>  
>  	if (unlikely(!dma_direct_possible(dev, dma_addr, size))) {
>  		report_addr(dev, dma_addr, size);
>
>
>
Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland


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Re: [PATCH 3/3] videobuf2: replace a layering violation with dma_map_resource

[Christoph Hellwig]

On Mon, Jan 14, 2019 at 01:42:26PM +0100, Marek Szyprowski wrote:
> Hi Christoph,
> 
> On 2019-01-11 19:17, Christoph Hellwig wrote:
> > vb2_dc_get_userptr pokes into arm direct mapping details to get the
> > resemblance of a dma address for a a physical address that does is
> > not backed by a page struct.  Not only is this not portable to other
> > architectures with dma direct mapping offsets, but also not to uses
> > of IOMMUs of any kind.  Switch to the proper dma_map_resource /
> > dma_unmap_resource interface instead.
> >
> > Signed-off-by: Christoph Hellwig <hch@lst.de>
> 
> There are checks for IOMMU presence in other places in vb2-dma-contig,
> so it was used only when no IOMMU is available, but I agree that the
> hacky code should be replaced by a generic code if possible.
> 
> Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
> 
> V4L2 pipeline works fine on older Exynos-based boards with CMA and IOMMU
> disabled.

Do you know if these rely on the offsets?  E.g. would they still work
with the patch below applied on top.  That would keep the map_resource
semantics as-is as solve the issue pointed out by Robin for now.

If not I can only think of a flag to bypass the offseting for now, but
that would be pretty ugly.  Or go for the long-term solution of
discovering the relationship between the two devices, as done by the
PCIe P2P code..

diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 8e0359b04957..25bd19974223 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -359,7 +359,7 @@ EXPORT_SYMBOL(dma_direct_map_sg);
 dma_addr_t dma_direct_map_resource(struct device *dev, phys_addr_t paddr,
 		size_t size, enum dma_data_direction dir, unsigned long attrs)
 {
-	dma_addr_t dma_addr = phys_to_dma(dev, paddr);
+	dma_addr_t dma_addr = paddr;
 
 	if (unlikely(!dma_direct_possible(dev, dma_addr, size))) {
 		report_addr(dev, dma_addr, size);


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Re: [PATCH 3/3] videobuf2: replace a layering violation with dma_map_resource

[Marek Szyprowski]

Hi Christoph,

On 2019-01-11 19:17, Christoph Hellwig wrote:
> vb2_dc_get_userptr pokes into arm direct mapping details to get the
> resemblance of a dma address for a a physical address that does is
> not backed by a page struct.  Not only is this not portable to other
> architectures with dma direct mapping offsets, but also not to uses
> of IOMMUs of any kind.  Switch to the proper dma_map_resource /
> dma_unmap_resource interface instead.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>

There are checks for IOMMU presence in other places in vb2-dma-contig,
so it was used only when no IOMMU is available, but I agree that the
hacky code should be replaced by a generic code if possible.

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

V4L2 pipeline works fine on older Exynos-based boards with CMA and IOMMU
disabled.

> ---
>  .../common/videobuf2/videobuf2-dma-contig.c   | 41 ++++---------------
>  1 file changed, 9 insertions(+), 32 deletions(-)
>
> diff --git a/drivers/media/common/videobuf2/videobuf2-dma-contig.c b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
> index aff0ab7bf83d..82389aead6ed 100644
> --- a/drivers/media/common/videobuf2/videobuf2-dma-contig.c
> +++ b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
> @@ -439,42 +439,14 @@ static void vb2_dc_put_userptr(void *buf_priv)
>  				set_page_dirty_lock(pages[i]);
>  		sg_free_table(sgt);
>  		kfree(sgt);
> +	} else {
> +		dma_unmap_resource(buf->dev, buf->dma_addr, buf->size,
> +				   buf->dma_dir, 0);
>  	}
>  	vb2_destroy_framevec(buf->vec);
>  	kfree(buf);
>  }
>  
> -/*
> - * For some kind of reserved memory there might be no struct page available,
> - * so all that can be done to support such 'pages' is to try to convert
> - * pfn to dma address or at the last resort just assume that
> - * dma address == physical address (like it has been assumed in earlier version
> - * of videobuf2-dma-contig
> - */
> -
> -#ifdef __arch_pfn_to_dma
> -static inline dma_addr_t vb2_dc_pfn_to_dma(struct device *dev, unsigned long pfn)
> -{
> -	return (dma_addr_t)__arch_pfn_to_dma(dev, pfn);
> -}
> -#elif defined(__pfn_to_bus)
> -static inline dma_addr_t vb2_dc_pfn_to_dma(struct device *dev, unsigned long pfn)
> -{
> -	return (dma_addr_t)__pfn_to_bus(pfn);
> -}
> -#elif defined(__pfn_to_phys)
> -static inline dma_addr_t vb2_dc_pfn_to_dma(struct device *dev, unsigned long pfn)
> -{
> -	return (dma_addr_t)__pfn_to_phys(pfn);
> -}
> -#else
> -static inline dma_addr_t vb2_dc_pfn_to_dma(struct device *dev, unsigned long pfn)
> -{
> -	/* really, we cannot do anything better at this point */
> -	return (dma_addr_t)(pfn) << PAGE_SHIFT;
> -}
> -#endif
> -
>  static void *vb2_dc_get_userptr(struct device *dev, unsigned long vaddr,
>  	unsigned long size, enum dma_data_direction dma_dir)
>  {
> @@ -528,7 +500,12 @@ static void *vb2_dc_get_userptr(struct device *dev, unsigned long vaddr,
>  		for (i = 1; i < n_pages; i++)
>  			if (nums[i-1] + 1 != nums[i])
>  				goto fail_pfnvec;
> -		buf->dma_addr = vb2_dc_pfn_to_dma(buf->dev, nums[0]);
> +		buf->dma_addr = dma_map_resource(buf->dev,
> +				__pfn_to_phys(nums[0]), size, buf->dma_dir, 0);
> +		if (dma_mapping_error(buf->dev, buf->dma_addr)) {
> +			ret = -ENOMEM;
> +			goto fail_pfnvec;
> +		}
>  		goto out;
>  	}
>  

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


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Re: [PATCH 3/3] videobuf2: replace a layering violation with dma_map_resource

[Christoph Hellwig]

On Mon, Jan 14, 2019 at 09:04:56AM -0200, Mauro Carvalho Chehab wrote:
> It would be good if you could later send us a stable branch where
> you merged, in order to allow us to run some tests with the new
> DMA mapping patchset and be sure that it won't cause regressions
> to videobuf2.

I can do that, but the series as sent should be testable, results
welcome!

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Re: [PATCH 3/3] videobuf2: replace a layering violation with dma_map_resource

[Mauro Carvalho Chehab]

Em Mon, 14 Jan 2019 11:31:39 +0100
Christoph Hellwig <hch@lst.de> escreveu:

> On Fri, Jan 11, 2019 at 05:54:16PM -0200, Mauro Carvalho Chehab wrote:
> > Em Fri, 11 Jan 2019 19:17:31 +0100
> > Christoph Hellwig <hch@lst.de> escreveu:
> >   
> > > vb2_dc_get_userptr pokes into arm direct mapping details to get the
> > > resemblance of a dma address for a a physical address that does is
> > > not backed by a page struct.  Not only is this not portable to other
> > > architectures with dma direct mapping offsets, but also not to uses
> > > of IOMMUs of any kind.  Switch to the proper dma_map_resource /
> > > dma_unmap_resource interface instead.  
> > 
> > Makes sense to me. I'm assuming that you'll be pushing it together
> > with other mm patches, so:  
> 
> Not really mm, but rather DMA mapping, but yes, I'd love to take it
> all together.

Ah, OK! Anyway, feel free to place it altogether. 

It would be good if you could later send us a stable branch where
you merged, in order to allow us to run some tests with the new
DMA mapping patchset and be sure that it won't cause regressions
to videobuf2.

Thank you!

Mauro

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Re: [PATCH 3/3] videobuf2: replace a layering violation with dma_map_resource

[Christoph Hellwig]

On Fri, Jan 11, 2019 at 05:54:16PM -0200, Mauro Carvalho Chehab wrote:
> Em Fri, 11 Jan 2019 19:17:31 +0100
> Christoph Hellwig <hch@lst.de> escreveu:
> 
> > vb2_dc_get_userptr pokes into arm direct mapping details to get the
> > resemblance of a dma address for a a physical address that does is
> > not backed by a page struct.  Not only is this not portable to other
> > architectures with dma direct mapping offsets, but also not to uses
> > of IOMMUs of any kind.  Switch to the proper dma_map_resource /
> > dma_unmap_resource interface instead.
> 
> Makes sense to me. I'm assuming that you'll be pushing it together
> with other mm patches, so:

Not really mm, but rather DMA mapping, but yes, I'd love to take it
all together.

Thanks!

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Re: [PATCH 3/3] videobuf2: replace a layering violation with dma_map_resource

[Mauro Carvalho Chehab]

Em Fri, 11 Jan 2019 19:17:31 +0100
Christoph Hellwig <hch@lst.de> escreveu:

> vb2_dc_get_userptr pokes into arm direct mapping details to get the
> resemblance of a dma address for a a physical address that does is
> not backed by a page struct.  Not only is this not portable to other
> architectures with dma direct mapping offsets, but also not to uses
> of IOMMUs of any kind.  Switch to the proper dma_map_resource /
> dma_unmap_resource interface instead.

Makes sense to me. I'm assuming that you'll be pushing it together
with other mm patches, so:

Acked-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  .../common/videobuf2/videobuf2-dma-contig.c   | 41 ++++---------------
>  1 file changed, 9 insertions(+), 32 deletions(-)
> 
> diff --git a/drivers/media/common/videobuf2/videobuf2-dma-contig.c b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
> index aff0ab7bf83d..82389aead6ed 100644
> --- a/drivers/media/common/videobuf2/videobuf2-dma-contig.c
> +++ b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
> @@ -439,42 +439,14 @@ static void vb2_dc_put_userptr(void *buf_priv)
>  				set_page_dirty_lock(pages[i]);
>  		sg_free_table(sgt);
>  		kfree(sgt);
> +	} else {
> +		dma_unmap_resource(buf->dev, buf->dma_addr, buf->size,
> +				   buf->dma_dir, 0);
>  	}
>  	vb2_destroy_framevec(buf->vec);
>  	kfree(buf);
>  }
>  
> -/*
> - * For some kind of reserved memory there might be no struct page available,
> - * so all that can be done to support such 'pages' is to try to convert
> - * pfn to dma address or at the last resort just assume that
> - * dma address == physical address (like it has been assumed in earlier version
> - * of videobuf2-dma-contig
> - */
> -
> -#ifdef __arch_pfn_to_dma
> -static inline dma_addr_t vb2_dc_pfn_to_dma(struct device *dev, unsigned long pfn)
> -{
> -	return (dma_addr_t)__arch_pfn_to_dma(dev, pfn);
> -}
> -#elif defined(__pfn_to_bus)
> -static inline dma_addr_t vb2_dc_pfn_to_dma(struct device *dev, unsigned long pfn)
> -{
> -	return (dma_addr_t)__pfn_to_bus(pfn);
> -}
> -#elif defined(__pfn_to_phys)
> -static inline dma_addr_t vb2_dc_pfn_to_dma(struct device *dev, unsigned long pfn)
> -{
> -	return (dma_addr_t)__pfn_to_phys(pfn);
> -}
> -#else
> -static inline dma_addr_t vb2_dc_pfn_to_dma(struct device *dev, unsigned long pfn)
> -{
> -	/* really, we cannot do anything better at this point */
> -	return (dma_addr_t)(pfn) << PAGE_SHIFT;
> -}
> -#endif
> -
>  static void *vb2_dc_get_userptr(struct device *dev, unsigned long vaddr,
>  	unsigned long size, enum dma_data_direction dma_dir)
>  {
> @@ -528,7 +500,12 @@ static void *vb2_dc_get_userptr(struct device *dev, unsigned long vaddr,
>  		for (i = 1; i < n_pages; i++)
>  			if (nums[i-1] + 1 != nums[i])
>  				goto fail_pfnvec;
> -		buf->dma_addr = vb2_dc_pfn_to_dma(buf->dev, nums[0]);
> +		buf->dma_addr = dma_map_resource(buf->dev,
> +				__pfn_to_phys(nums[0]), size, buf->dma_dir, 0);
> +		if (dma_mapping_error(buf->dev, buf->dma_addr)) {
> +			ret = -ENOMEM;
> +			goto fail_pfnvec;
> +		}
>  		goto out;
>  	}
>  



Thanks,
Mauro

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[PATCH 3/3] videobuf2: replace a layering violation with dma_map_resource

[Christoph Hellwig]

vb2_dc_get_userptr pokes into arm direct mapping details to get the
resemblance of a dma address for a a physical address that does is
not backed by a page struct.  Not only is this not portable to other
architectures with dma direct mapping offsets, but also not to uses
of IOMMUs of any kind.  Switch to the proper dma_map_resource /
dma_unmap_resource interface instead.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 .../common/videobuf2/videobuf2-dma-contig.c   | 41 ++++---------------
 1 file changed, 9 insertions(+), 32 deletions(-)

diff --git a/drivers/media/common/videobuf2/videobuf2-dma-contig.c b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
index aff0ab7bf83d..82389aead6ed 100644
--- a/drivers/media/common/videobuf2/videobuf2-dma-contig.c
+++ b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
@@ -439,42 +439,14 @@ static void vb2_dc_put_userptr(void *buf_priv)
 				set_page_dirty_lock(pages[i]);
 		sg_free_table(sgt);
 		kfree(sgt);
+	} else {
+		dma_unmap_resource(buf->dev, buf->dma_addr, buf->size,
+				   buf->dma_dir, 0);
 	}
 	vb2_destroy_framevec(buf->vec);
 	kfree(buf);
 }
 
-/*
- * For some kind of reserved memory there might be no struct page available,
- * so all that can be done to support such 'pages' is to try to convert
- * pfn to dma address or at the last resort just assume that
- * dma address == physical address (like it has been assumed in earlier version
- * of videobuf2-dma-contig
- */
-
-#ifdef __arch_pfn_to_dma
-static inline dma_addr_t vb2_dc_pfn_to_dma(struct device *dev, unsigned long pfn)
-{
-	return (dma_addr_t)__arch_pfn_to_dma(dev, pfn);
-}
-#elif defined(__pfn_to_bus)
-static inline dma_addr_t vb2_dc_pfn_to_dma(struct device *dev, unsigned long pfn)
-{
-	return (dma_addr_t)__pfn_to_bus(pfn);
-}
-#elif defined(__pfn_to_phys)
-static inline dma_addr_t vb2_dc_pfn_to_dma(struct device *dev, unsigned long pfn)
-{
-	return (dma_addr_t)__pfn_to_phys(pfn);
-}
-#else
-static inline dma_addr_t vb2_dc_pfn_to_dma(struct device *dev, unsigned long pfn)
-{
-	/* really, we cannot do anything better at this point */
-	return (dma_addr_t)(pfn) << PAGE_SHIFT;
-}
-#endif
-
 static void *vb2_dc_get_userptr(struct device *dev, unsigned long vaddr,
 	unsigned long size, enum dma_data_direction dma_dir)
 {
@@ -528,7 +500,12 @@ static void *vb2_dc_get_userptr(struct device *dev, unsigned long vaddr,
 		for (i = 1; i < n_pages; i++)
 			if (nums[i-1] + 1 != nums[i])
 				goto fail_pfnvec;
-		buf->dma_addr = vb2_dc_pfn_to_dma(buf->dev, nums[0]);
+		buf->dma_addr = dma_map_resource(buf->dev,
+				__pfn_to_phys(nums[0]), size, buf->dma_dir, 0);
+		if (dma_mapping_error(buf->dev, buf->dma_addr)) {
+			ret = -ENOMEM;
+			goto fail_pfnvec;
+		}
 		goto out;
 	}
 
-- 
2.20.1


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