linux-kernel - Re: [PATCH] dma: pl330: Add support for DMA

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Date:	Wed, 14 May 2014 18:46:32 +0530
From:	Jassi Brar <jassisinghbrar@...il.com>
To:	Tushar Behera <tushar.behera@...aro.org>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	dmaengine@...r.kernel.org, Vinod Koul <vinod.koul@...el.com>,
	Dan Williams <dan.j.williams@...el.com>
Subject: Re: [PATCH] dma: pl330: Add support for DMA_PAUSE command

On Wed, May 14, 2014 at 5:37 PM, Tushar Behera <tushar.behera@...aro.org> wrote:
> On 14 May 2014 17:29, Jassi Brar <jassisinghbrar@...il.com> wrote:
>> On Wed, May 14, 2014 at 8:53 AM, Tushar Behera <tushar.behera@...aro.org> wrote:
>>> While playing back audio, pmc_dmaengine requests the DMA channel to
>>> stop DMA transmission through DMA_PAUSE command.
>>>
>>> Currently PL330 driver doesn't support DMA pause command, leaving
>>> the DMA state inconsistent when the system resumes. Instead, it would
>>> be better to terminate the DMA transfer during suspend and restart
>>> again during resume.
>>>
>>> Tested with audio playback across a suspend-resume cycle.
>>>
>> What is pmc_dmaengine? How does DMA_PAUSE help, when there is no DMA_RESUME?
>>
>
> Sorry, it is a typo.
>
> sound/core/pcm_dmaengine.c:snd_dmaengine_pcm_trigger() -->
> dmaengine_pause() is called during system suspend.
>
pl330.c does specify  cmd_pause = false, which should prevent
sound/soc/soc-generic-dmaengine-pcm.c:dmaengine_pcm_set_runtime_hwparams()
from declaring PAUSE/RESUME support. Which kernel are you using?

-jassi
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