linux-kernel - Re: [PATCH 1/3] crypto: marvell/cesa - replace dma_to_phys with dma_map

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Date:	Thu, 17 Mar 2016 22:54:59 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Sinan Kaya <okaya@...eaurora.org>
Cc:	linux-arm-kernel@...ts.infradead.org, timur@...eaurora.org,
	cov@...eaurora.org, nwatters@...eaurora.org,
	Boris Brezillon <boris.brezillon@...e-electrons.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Arnaud Ebalard <arno@...isbad.org>,
	linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH 1/3] crypto: marvell/cesa - replace dma_to_phys with
 dma_map_single

On Thu, Mar 17, 2016 at 06:02:15PM -0400, Sinan Kaya wrote:
> Getting ready to remove dma_to_phys API. Drivers should not be
> using this API for DMA operations. Instead, they should go
> through the dma_map or dma_alloc APIs.
> 
> Signed-off-by: Sinan Kaya <okaya@...eaurora.org>
> ---
>  drivers/crypto/marvell/cesa.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/crypto/marvell/cesa.c b/drivers/crypto/marvell/cesa.c
> index c0656e7..52ddfa4 100644
> --- a/drivers/crypto/marvell/cesa.c
> +++ b/drivers/crypto/marvell/cesa.c
> @@ -350,8 +350,8 @@ static int mv_cesa_get_sram(struct platform_device *pdev, int idx)
>  	if (IS_ERR(engine->sram))
>  		return PTR_ERR(engine->sram);
>  
> -	engine->sram_dma = phys_to_dma(cesa->dev,
> -				       (phys_addr_t)res->start);
> +	engine->sram_dma = dma_map_single(cesa->dev, engine->sram,
> +					  DMA_TO_DEVICE);

Documentation/DMA-API.txt

dma_addr_t
dma_map_single(struct device *dev, void *cpu_addr, size_t size,
                      enum dma_data_direction direction)

Notes:  Not all memory regions in a machine can be mapped by this API.
Further, contiguous kernel virtual space may not be contiguous as
physical memory.  Since this API does not provide any scatter/gather
capability, it will fail if the user tries to map a non-physically
contiguous piece of memory.  For this reason, memory to be mapped by
this API should be obtained from sources which guarantee it to be
physically contiguous (like kmalloc).

Specifically, ioremapped memory will *not* work as you expect with
dma_map_single().

-- 
RMK's Patch system: http://www.arm.linux.org.uk/developer/patches/
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