Re: [PATCH 2/2 v2] dmaengine: rcar-audmapp: independent from SH_DMAE_BASE v2

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

On Tue, Dec 16, 2014 at 09:03:38AM +0000, Kuninori Morimoto wrote:
> 
> Hi Vinod
> 
> > > This rcar-audmapp driver is very limited usage, and user is only sound device/driver.
> > > Sound driver configures both 1st/2nd DMAC if needed (it depends on platform).
> > > Sound driver knows all reg address / mem address which are needed for 1st/2nd DMAC settings.
> > > 1st/2nd DMAC needs general DMAEngine settings method, not special. 
> > > Now, sound driver + 1st/2nd DMAC works well on my local environment.
> > Are you not using the sound dmaengine library then, right?
> 
> At this point, yes.
> But, I got request from Mark to use it
Yes that is the subsytem recommendation

> # current dmaengine "method" on my driver is same as library.
> # but I need to fix non-dmaengine area
> 
> > One more question, audio data will be in system memory and then it needs to
> > be transfered to periphral FIFO, how will data travel thru these two DMAs?
> 
> like this
> 
>     1st DMA            2nd DMA
> [mem] -> [periphral IP-A] -> [periphral IP-B] -> speaker
Okay and by current implementation you wont be able to use the generic
dmaengine sound layer. That layer assumes you will have only one dmaengine
channel to configure and will configure only one DMA and which is 1st DMA
here.

So what do we do we 2nd one here. The point that 2nd DMA is behind the 1st
DMA, should the users know about it and configure? I am not sure...
If not, then who should configure this. Another candidate is 1st DMA, but
then from the point of 1st DMA should it configure 2nd DMA as well, treat it
as its salve... sounds plausible but am not too sure... comments?

-- 
~Vinod