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

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Date:	Fri, 1 Jun 2012 17:13:45 +0900
From:	Tomoya MORINAGA <tomoya.rohm@...il.com>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
Cc:	Vinod Koul <vinod.koul@...ux.intel.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 Thu, May 31, 2012 at 7:45 PM, Mark Brown
<broonie@...nsource.wolfsonmicro.com> wrote:
>> > Please re-read what I wrote.
>
>> Let me clarify.
>> Do you say native DMA driver API like dmaengine_prep_slave_sg(),
>> dmaengine_submit() shouldn't be used from ASoC driver, right ?
>
> Your driver should be written in terms of the ASoC DMA framework.

I understand your order.
But isn't it only me ?
You mean all ASoC driver uses dmaengine should be written in terms of
the ASoC DMA framework.
Right ?

>> > No, all current mainline drivers using the library use cyclic DMA.
>> I can't see any driver uses cyclic DMA. (I saw linux-next's tree from
>> kernel.org.)
>> Where is your saying "current mainline" ?
> Linus' tree, or mine.

Sorry, I couldn't find.
Is your saying Linus's tree this ?
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
However, any ASoC driver doesn't use cyclic DMA's.


> Have you even looked at the soc-dmaengine-pcm
> code?  It uncondtionally requests a cyclic channel.

I already saw soc-dmaengine-pcm.c

>> However I think it seems difficult for supporting all devices.
>> Because hardware dependency control code can't be added.
>> For example, for ML7213, needs interrupt control both before/after DMA transfer.
>> However,  in case of using soc-dmaengine, the control can't be done.
>> Because the processing is in soc-dmaengine.
> Please be more specific.  What are the concrete problems that you see?
> Why is it not possible to address them within the framework?

I show the code.
+static void i2s_dma_tx_complete(void *arg)
+{
...

+
+       ioh_i2s_irq_ctrl(ioh->number, SNDRV_PCM_STREAM_PLAYBACK,
IOH_EN_IRQ);   ##<<Interrupt control
+}

Our device needs interrupt control both before/after DMA transfer like above.
In your soc-dma-engine, DMA transfer complete code is in soc-dma-engine, right ?
So, the vendor specific code like the above can't be written.

thanks.
-- 
ROHM Co., Ltd.
tomoya
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