Re: [PATCH 12/12] ARM: mmu: Make sure DMA coherent memory is zeroed out

[Sam Ravnborg <sam@ravnborg.org>]

Hi Andrey.

On Wed, Jan 16, 2019 at 10:38:40PM -0800, Andrey Smirnov wrote:
> In order to avoid passing random/junky values to DMA/HW as well as to
> allow simplifying memory initialization in individual drivers, chagnge
chagnge => change

> dma_alloc_coherent() to guarantee that memory it returs is properly
returs => returns
> zeroed out.
> 
> Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
> ---
>  arch/arm/cpu/mmu-common.c | 3 ++-
>  arch/arm/cpu/mmu-common.h | 1 +
>  arch/arm/cpu/mmu.c        | 2 +-
>  arch/arm/cpu/mmu_64.c     | 8 ++++++++
>  4 files changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm/cpu/mmu-common.c b/arch/arm/cpu/mmu-common.c
> index c5b24bff8..aeefbb2da 100644
> --- a/arch/arm/cpu/mmu-common.c
> +++ b/arch/arm/cpu/mmu-common.c
> @@ -43,7 +43,8 @@ void *dma_alloc_map(size_t size, dma_addr_t *dma_handle, unsigned flags)
>  	if (dma_handle)
>  		*dma_handle = (dma_addr_t)ret;
>  
> -	dma_inv_range(ret, size);
> +	memset(ret, 0, size);
> +	dma_flush_range(ret, size);
>  
>  	arch_remap_range(ret, size, flags);
>  
> diff --git a/arch/arm/cpu/mmu-common.h b/arch/arm/cpu/mmu-common.h
> index 679799c3c..0a33b138e 100644
> --- a/arch/arm/cpu/mmu-common.h
> +++ b/arch/arm/cpu/mmu-common.h
> @@ -2,6 +2,7 @@
>  #define __ARM_MMU_COMMON_H
>  
>  void dma_inv_range(void *ptr, size_t size);
> +void dma_flush_range(void *ptr, size_t size);
>  void *dma_alloc_map(size_t size, dma_addr_t *dma_handle, unsigned flags);
>  void __mmu_init(bool mmu_on);
>  
> diff --git a/arch/arm/cpu/mmu.c b/arch/arm/cpu/mmu.c
> index 9e261a0be..29816ad56 100644
> --- a/arch/arm/cpu/mmu.c
> +++ b/arch/arm/cpu/mmu.c
> @@ -97,7 +97,7 @@ static u32 *find_pte(unsigned long adr)
>  	return &table[(adr >> PAGE_SHIFT) & 0xff];
>  }
>  
> -static void dma_flush_range(void *ptr, size_t size)
> +void dma_flush_range(void *ptr, size_t size)
>  {
>  	unsigned long start = (unsigned long)ptr;
>  	unsigned long end = start + size;
> diff --git a/arch/arm/cpu/mmu_64.c b/arch/arm/cpu/mmu_64.c
> index a3074b10d..b45a69661 100644
> --- a/arch/arm/cpu/mmu_64.c
> +++ b/arch/arm/cpu/mmu_64.c
> @@ -233,6 +233,14 @@ void dma_inv_range(void *ptr, size_t size)
>  	v8_inv_dcache_range(start, end);
>  }
>  
> +void dma_flush_range(void *ptr, size_t size)
> +{
> +	unsigned long start = (unsigned long)ptr;
> +	unsigned long end = start + size - 1;
> +
> +	v8_flush_dcache_range(start, end);
> +}
We should use the existing indirection with struct cache_fns
here, then we could share the code.

	Sam

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