linux-kernel - Re: [alsa-devel] [PATCH v5] sound/soc/lapis: add platform driver for ML7213

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Message-ID: <1337941231.1580.19.camel@vkoul-udesk3>
Date:	Fri, 25 May 2012 15:50:31 +0530
From:	Vinod Koul <vinod.koul@...ux.intel.com>
To:	Tomoya MORINAGA <tomoya.rohm@...il.com>
Cc:	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	alsa-devel@...a-project.org, lars@...afoo.de,
	Takashi Iwai <tiwai@...e.de>, linux-kernel@...r.kernel.org,
	Liam Girdwood <lrg@...com>
Subject: Re: [alsa-devel] [PATCH v5] sound/soc/lapis: add platform driver
 for ML7213

On Fri, 2012-05-25 at 18:30 +0900, Tomoya MORINAGA wrote:
> On Thu, May 24, 2012 at 7:07 PM, Mark Brown
> <broonie@...nsource.wolfsonmicro.com> wrote:
> >> > Nobody seems to be working on it as far as I can tell, I've certainly
> >> > not seen any patches.
> >
> >> If so, could you accept current platform/machine driver ?
> >
> > Ideally what would be happening here is that you or other people who
> > have such systems would be working to add the required support to the
> > core code, there's clearly a need for common code here as there are a
> > number of different systems that don't have cyclic DMA and it wouldn't
> > be great to end up with duplicated code.
> >
> > Is there some great difficulty in factoring out the support for
> > non-cyclic audio DMA on dmaengine - it seems like if there is we must
> > have a serious problem in dmaengine which we should fix?  If there is a
> > substantial difficulty then that's different but it doesn't feel like
> > we've tried doing common code yet, if there's problems doing that I'd
> > like to understand what they are before we jump ahead of ourselves.
> 
> I'm not so familiar with Linux's DMA idea.
> So we don't know whether non-cyclic dmaengine has problem or not.
First you should not be writing your own dma driver, it *needs* to use
dmaenegine. We already have bunch of driver supported, so there may be a
case that existing driver works straight or with little modifications.
Using your own dma driver is a dead road, so sooner you move over better
it is.

One you move then it would be easy for you to use soc-dmaengine. If your
driver doesn't support cyclic; nothing stops from you emulating that in
S/W. And given that you have already contributed to dmaengine subsystem,
it should be easy for you :)
> 
> Until now, we've developed device drivers use DMA driver like UART, SPI.
> These drivers are  implemented using the same way, you called
> "non-cyclic", and already applied.
> 
> As you said, common code for DMA code can be best solution.
> However, currently, the code is nothing.
> So, I want you to accept our driver as first step.
> Because I think supporting new device is more important for linux than
> dmaengine common.
> 
> thanks


-- 
~Vinod

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