Re: [PATCH] arm64: Add support for DMA_ATTR_SKIP_CPU_SYNC attribute to swiotlb

[Will Deacon]

On Wed, Jan 11, 2017 at 11:11:17AM +0100, Geert Uytterhoeven wrote:
> From: Takeshi Kihara 
> 
> This patch adds support for DMA_ATTR_SKIP_CPU_SYNC attribute for
> dma_{un}map_{page,sg} functions family to swiotlb.
> 
> DMA_ATTR_SKIP_CPU_SYNC allows platform code to skip synchronization of
> the CPU cache for the given buffer assuming that it has been already
> transferred to 'device' domain.
> 
> Ported from IOMMU .{un}map_{sg,page} ops.
> 
> Signed-off-by: Takeshi Kihara 
> Acked-by: Laurent Pinchart 
> Signed-off-by: Geert Uytterhoeven 
> ---
> v2:
>   - Add Acked-by.
> 
> Support for DMA_ATTR_SKIP_CPU_SYNC was included when porting the IOMMU
> ops from arm to arm64 in commit 13b8629f651164d7 ("arm64: Add IOMMU
> dma_ops").
> 
> Presumably it was an oversight that the existing swiotlb based
> implementation didn't have support for DMA_ATTR_SKIP_CPU_SYNC yet?
> ---
>  arch/arm64/mm/dma-mapping.c | 12 
>  1 file changed, 8 insertions(+), 4 deletions(-)

Thanks. Applied for 4.11, with Robin's Reviewed-by.

Will

Re: [PATCH] arm64: Add support for DMA_ATTR_SKIP_CPU_SYNC attribute to swiotlb

[Robin Murphy]

On 11/01/17 10:11, Geert Uytterhoeven wrote:
> From: Takeshi Kihara 
> 
> This patch adds support for DMA_ATTR_SKIP_CPU_SYNC attribute for
> dma_{un}map_{page,sg} functions family to swiotlb.
> 
> DMA_ATTR_SKIP_CPU_SYNC allows platform code to skip synchronization of
> the CPU cache for the given buffer assuming that it has been already
> transferred to 'device' domain.
> 
> Ported from IOMMU .{un}map_{sg,page} ops.
> 
> Signed-off-by: Takeshi Kihara 
> Acked-by: Laurent Pinchart 
> Signed-off-by: Geert Uytterhoeven 
> ---
> v2:
>   - Add Acked-by.
> 
> Support for DMA_ATTR_SKIP_CPU_SYNC was included when porting the IOMMU
> ops from arm to arm64 in commit 13b8629f651164d7 ("arm64: Add IOMMU
> dma_ops").
> 
> Presumably it was an oversight that the existing swiotlb based
> implementation didn't have support for DMA_ATTR_SKIP_CPU_SYNC yet?

Less an oversight, more that nobody's wanted to use it until now ;)

Personally I'd prefer flag tests to be "!(x)" rather than "(x) == 0",
but the latter is already in place, so I'll leave the final word on
style/consistency nitpicks to Catalin and Will.

Reviewed-by: Robin Murphy 

> ---
>  arch/arm64/mm/dma-mapping.c | 12 
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
> index e04082700bb16c35..1d7d5d2881db7c19 100644
> --- a/arch/arm64/mm/dma-mapping.c
> +++ b/arch/arm64/mm/dma-mapping.c
> @@ -211,7 +211,8 @@ static dma_addr_t __swiotlb_map_page(struct device *dev, 
> struct page *page,
>   dma_addr_t dev_addr;
>  
>   dev_addr = swiotlb_map_page(dev, page, offset, size, dir, attrs);
> - if (!is_device_dma_coherent(dev))
> + if (!is_device_dma_coherent(dev) &&
> + (attrs & DMA_ATTR_SKIP_CPU_SYNC) == 0)
>   __dma_map_area(phys_to_virt(dma_to_phys(dev, dev_addr)), size, 
> dir);
>  
>   return dev_addr;
> @@ -222,7 +223,8 @@ static void __swiotlb_unmap_page(struct device *dev, 
> dma_addr_t dev_addr,
>size_t size, enum dma_data_direction dir,
>unsigned long attrs)
>  {
> - if (!is_device_dma_coherent(dev))
> + if (!is_device_dma_coherent(dev) &&
> + (attrs & DMA_ATTR_SKIP_CPU_SYNC) == 0)
>   __dma_unmap_area(phys_to_virt(dma_to_phys(dev, dev_addr)), 
> size, dir);
>   swiotlb_unmap_page(dev, dev_addr, size, dir, attrs);
>  }
> @@ -235,7 +237,8 @@ static int __swiotlb_map_sg_attrs(struct device *dev, 
> struct scatterlist *sgl,
>   int i, ret;
>  
>   ret = swiotlb_map_sg_attrs(dev, sgl, nelems, dir, attrs);
> - if (!is_device_dma_coherent(dev))
> + if (!is_device_dma_coherent(dev) &&
> + (attrs & DMA_ATTR_SKIP_CPU_SYNC) == 0)
>   for_each_sg(sgl, sg, ret, i)
>   __dma_map_area(phys_to_virt(dma_to_phys(dev, 
> sg->dma_address)),
>  sg->length, dir);
> @@ -251,7 +254,8 @@ static void __swiotlb_unmap_sg_attrs(struct device *dev,
>   struct scatterlist *sg;
>   int i;
>  
> - if (!is_device_dma_coherent(dev))
> + if (!is_device_dma_coherent(dev) &&
> + (attrs & DMA_ATTR_SKIP_CPU_SYNC) == 0)
>   for_each_sg(sgl, sg, nelems, i)
>   __dma_unmap_area(phys_to_virt(dma_to_phys(dev, 
> sg->dma_address)),
>sg->length, dir);
> 

[PATCH] arm64: Add support for DMA_ATTR_SKIP_CPU_SYNC attribute to swiotlb

[Geert Uytterhoeven]

From: Takeshi Kihara 

This patch adds support for DMA_ATTR_SKIP_CPU_SYNC attribute for
dma_{un}map_{page,sg} functions family to swiotlb.

DMA_ATTR_SKIP_CPU_SYNC allows platform code to skip synchronization of
the CPU cache for the given buffer assuming that it has been already
transferred to 'device' domain.

Ported from IOMMU .{un}map_{sg,page} ops.

Signed-off-by: Takeshi Kihara 
Acked-by: Laurent Pinchart 
Signed-off-by: Geert Uytterhoeven 
---
v2:
  - Add Acked-by.

Support for DMA_ATTR_SKIP_CPU_SYNC was included when porting the IOMMU
ops from arm to arm64 in commit 13b8629f651164d7 ("arm64: Add IOMMU
dma_ops").

Presumably it was an oversight that the existing swiotlb based
implementation didn't have support for DMA_ATTR_SKIP_CPU_SYNC yet?
---
 arch/arm64/mm/dma-mapping.c | 12 
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
index e04082700bb16c35..1d7d5d2881db7c19 100644
--- a/arch/arm64/mm/dma-mapping.c
+++ b/arch/arm64/mm/dma-mapping.c
@@ -211,7 +211,8 @@ static dma_addr_t __swiotlb_map_page(struct device *dev, 
struct page *page,
dma_addr_t dev_addr;
 
dev_addr = swiotlb_map_page(dev, page, offset, size, dir, attrs);
-   if (!is_device_dma_coherent(dev))
+   if (!is_device_dma_coherent(dev) &&
+   (attrs & DMA_ATTR_SKIP_CPU_SYNC) == 0)
__dma_map_area(phys_to_virt(dma_to_phys(dev, dev_addr)), size, 
dir);
 
return dev_addr;
@@ -222,7 +223,8 @@ static void __swiotlb_unmap_page(struct device *dev, 
dma_addr_t dev_addr,
 size_t size, enum dma_data_direction dir,
 unsigned long attrs)
 {
-   if (!is_device_dma_coherent(dev))
+   if (!is_device_dma_coherent(dev) &&
+   (attrs & DMA_ATTR_SKIP_CPU_SYNC) == 0)
__dma_unmap_area(phys_to_virt(dma_to_phys(dev, dev_addr)), 
size, dir);
swiotlb_unmap_page(dev, dev_addr, size, dir, attrs);
 }
@@ -235,7 +237,8 @@ static int __swiotlb_map_sg_attrs(struct device *dev, 
struct scatterlist *sgl,
int i, ret;
 
ret = swiotlb_map_sg_attrs(dev, sgl, nelems, dir, attrs);
-   if (!is_device_dma_coherent(dev))
+   if (!is_device_dma_coherent(dev) &&
+   (attrs & DMA_ATTR_SKIP_CPU_SYNC) == 0)
for_each_sg(sgl, sg, ret, i)
__dma_map_area(phys_to_virt(dma_to_phys(dev, 
sg->dma_address)),
   sg->length, dir);
@@ -251,7 +254,8 @@ static void __swiotlb_unmap_sg_attrs(struct device *dev,
struct scatterlist *sg;
int i;
 
-   if (!is_device_dma_coherent(dev))
+   if (!is_device_dma_coherent(dev) &&
+   (attrs & DMA_ATTR_SKIP_CPU_SYNC) == 0)
for_each_sg(sgl, sg, nelems, i)
__dma_unmap_area(phys_to_virt(dma_to_phys(dev, 
sg->dma_address)),
 sg->length, dir);
-- 
1.9.1