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

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Date:	Sat, 30 Jun 2012 20:38:29 +0530
From:	Laxman Dewangan <ldewangan@...dia.com>
To:	Stephen Warren <swarren@...dotorg.org>
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 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:
>
>> # aplay ~/abba-dq-48000-stereo.wav
>> [  151.613476] tegra20-i2s tegra20-i2s.0: dmaengine pcm open failed with err -6
>> [  151.620557] tegra20-i2s tegra20-i2s.0: can't open platform tegra20-i2s.0: -6
>> aplay: main:654: audio open error: No such device or address

With the error, it seems that dmachannel is not getting allocated.

> I do have the following in my local tree:
> 68a67b8 ARM: tegra: add device tree AUXDATA for APBDMA
> 0db7a96 ARM: tegra: dma: rename driver name for clock to "tegra-apbdma"
>

Some dma changes which I sent and already on linux-next are also require 
with the above change.
Alsong with that I have local change like to rename the dma driver to 
compatible with dts files (remove -new from driver).

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.


> I also fixed the compatible values in drivers/dma/tegra20-apb-dma.c so
> the driver would get instantiated, which it does;
> /sys/devices/tegra-apbdma/dma has a bunch of dmaengine channels in it.
>

Possibly some patches in dma driver  which is already applied in next is 
not available in your tree. CYCLIC_DMA patch is important.

> (Note: This is on Ventana, although I doubt that makes much difference)
>

I tested on cardhu only but it should not matter.

> Is there something else I need to do to test this?

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