Re: [PATCH 0/3 v3][RFC] dmaengine: rcar-audmapp: calculate chcr via src/dst addr

[Vinod Koul <vinod.koul@intel.com>]

On Mon, Feb 16, 2015 at 08:47:00PM +0100, Arnd Bergmann wrote:
> On Monday 09 February 2015 01:37:41 Kuninori Morimoto wrote:
> > 
> > Hi Vinod, Arnd
> > 
> > Can I have feedback from you about below mail, and this patch ?
> > 
> > http://thread.gmane.org/gmane.linux.ports.sh.devel/41063/focusC372
> 
> I had the chance to discuss this in more depth with Laurent last
> week. What it basically comes down to is that you try to do something
> that the existing DT binding and slave API does not support: we
> only really do DMA_DEV_TO_MEM or DMA_MEM_TO_DEV, but not DMA_DEV_TO_DEV.
For the record, device_prep_slave_sg() can do DMA_DEV_TO_DEV. That is the
sole reason why dma_slave_config has both the directions for every field.

HTH

-- 
~Vinod
 
> To properly support this with the dmaengine API, we would likely first
> need to extend the generic DT binding, and then implement the driver
> to use that extended binding.
> 
> The easiest way out however seems to be to move the audmapp
> implementation into the rcar audio driver itself. As Laurent pointed
> out, it is not really a general-purpose dmaengine anyway and it
> only ever gets used by one driver, so we could not find any downsides.
> 
> 	Arnd
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