linux-kernel - Re: [PATCH] ASoC: tegra: use dmaengine based dma driver

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Date:	Mon, 02 Jul 2012 10:45:01 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Laxman Dewangan <ldewangan@...dia.com>
CC:	"tiwai@...e.de" <tiwai@...e.de>, "perex@...ex.cz" <perex@...ex.cz>,
	Stephen Warren <swarren@...dia.com>,
	"broonie@...nsource.wolfsonmicro.com" 
	<broonie@...nsource.wolfsonmicro.com>, "lrg@...com" <lrg@...com>,
	"alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH] ASoC: tegra: use dmaengine based dma driver

On 07/02/2012 02:25 AM, Laxman Dewangan wrote:
> On Saturday 30 June 2012 08:38 PM, Laxman Dewangan wrote:
>> On Friday 29 June 2012 10:32 PM, Stephen Warren wrote:
>>> On 06/29/2012 05:34 AM, Laxman Dewangan wrote:
>>>> Use the dmaengine based Tegra APB DMA driver for
>>>> data transfer between SPI fifo and memory in
>>>> place of legacy Tegra APB DMA.
>>>>
>>>> Because generic soc-dmaengine-pcm uses the DMAs API
>>>> based on dmaengine, using the exported APIs provided
>>>> by this generic driver.
>>>>
>>>> The new driver is selected if legacy driver is not
>>>> selected and new dma driver is enabled through config
>>>> file.
>>>
>>> This works just fine with the existing non-dmaengine DMA driver enabled.
>>>
>>> However, I can't get it to work with dmaengine:
...
>> I think I should send that patches so that you can test it by:
>> - Taking already applied dma driver change in linux-next.
>> - Apply my new patches which I am going to send.
>>
>> And do local change in the tegra_defconfig to disable SYSTEM_DMA and
>> enable dmaengine based dma driver.
>
> The new dma patches are:
> 
>  dma: tegra: fix residual calculation for cyclic case
>  dma: tegra: rename driver and compatible to match with dts
> ...

OK, with those two patches plus this one, everything works on
Cardhu/Tegra30 using dmaengine. However, on Tegra20 DMA doesn't appear
to work. No audio is heard, and aplay eventually exits with the
following error message:

aplay: pcm_write:1603: write error: Input/output error

I believe this means that the DMA simply isn't operating.

I'll assume this is a Tegra20-specific issue in the dmaengine driver
itself, and hence not a problem with this patch, so I'll ack this patch.
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