linux-kernel - Re: [PATCH] arc: Implement arch-specific dma_map

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Date:   Wed, 2 Nov 2016 11:08:06 -0600
From:   Catalin Marinas <catalin.marinas@....com>
To:     Alexey Brodkin <Alexey.Brodkin@...opsys.com>
Cc:     linux-snps-arc@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org,
        Vineet Gupta <Vineet.Gupta1@...opsys.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        stable@...r.kernel.org
Subject: Re: [PATCH] arc: Implement arch-specific dma_map_ops.mmap

On Wed, Nov 02, 2016 at 03:19:43PM +0300, Alexey Brodkin wrote:
> diff --git a/arch/arc/mm/dma.c b/arch/arc/mm/dma.c
> index 20afc65e22dc..034ec6a8a764 100644
> --- a/arch/arc/mm/dma.c
> +++ b/arch/arc/mm/dma.c
> @@ -105,6 +105,31 @@ static void arc_dma_free(struct device *dev, size_t size, void *vaddr,
>  	__free_pages(page, get_order(size));
>  }
>  
> +static int arc_dma_mmap(struct device *dev, struct vm_area_struct *vma,
> +			void *cpu_addr, dma_addr_t dma_addr, size_t size,
> +			unsigned long attrs)
> +{
> +	unsigned long user_count = vma_pages(vma);
> +	unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT;
> +	unsigned long pfn = __phys_to_pfn(dma_addr);

I don't think that's correct in all situations. Better as (for arc):

	unsigned long pfn = __phys_to_pfn(plat_dma_to_phys(dma_addr));

Other than that:

Reviewed-by: Catalin Marinas <catalin.marinas@....com>