linux-kernel - Re: [PATCH 1/2] mips: Fix mips_dma_map_sg by using correct dma mapping function

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Message-ID: <20180711160342.ddvlqvjp3smwyido@pburton-laptop>
Date:   Wed, 11 Jul 2018 09:03:42 -0700
From:   Paul Burton <paul.burton@...s.com>
To:     Thomas Bogendoerfer <tbogendoerfer@...e.de>
Cc:     Ralf Baechle <ralf@...ux-mips.org>,
        James Hogan <jhogan@...nel.org>, linux-mips@...ux-mips.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] mips: Fix mips_dma_map_sg by using correct dma
 mapping function

Hi Thomas,

On Wed, Jul 11, 2018 at 01:38:51PM +0200, Thomas Bogendoerfer wrote:
> sg list elements could cover more than one page of data. Therefore
> using plat_map_dma_mem_page() doesn't work for platforms, which have
> IOMMU functionality hidden behind plat_map_dma_XXX functions.
> 
> Fixes: e36863a550da ("MIPS: HIGHMEM DMA on noncoherent MIPS32 processors")
> Signed-off-by: Thomas Bogendoerfer <tbogendoerfer@...e.de>
> ---
>  arch/mips/mm/dma-default.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/mips/mm/dma-default.c b/arch/mips/mm/dma-default.c
> index f9fef0028ca2..2718185a3d38 100644
> --- a/arch/mips/mm/dma-default.c
> +++ b/arch/mips/mm/dma-default.c
> @@ -288,8 +288,8 @@ static int mips_dma_map_sg(struct device *dev, struct scatterlist *sglist,
>  #ifdef CONFIG_NEED_SG_DMA_LENGTH
>  		sg->dma_length = sg->length;
>  #endif
> -		sg->dma_address = plat_map_dma_mem_page(dev, sg_page(sg)) +
> -				  sg->offset;
> +		sg->dma_address = plat_map_dma_mem(dev, sg_virt(sg),
> +						   sg->length);
>  	}
>  
>  	return nents;

This doesn't apply after Christoph's massive MIPS DMA cleanup which can
be found in mips-next (or linux-next). After this work we end up using
the generic dma_direct_map_sg() on most systems, and the code above has
been removed.

Thanks,
    Paul