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Date: Wed, 20 Jun 2012 21:41:32 +0800
From: Dong Aisheng <aisheng.dong@freescale.com>
To: Lars-Peter Clausen <lars@metafoo.de>
CC: Mark Brown <broonie@opensource.wolfsonmicro.com>,
        Liam Girdwood <lrg@ti.com>, Vinod Koul <vinod.koul@intel.com>,
        Ola Lilja <ola.o.lilja@stericsson.com>, <alsa-devel@alsa-project.org>,
        Russell King <linux@arm.linux.org.uk>,
        Mika Westerberg <mika.westerberg@iki.fi>,
        <linux-kernel@vger.kernel.org>, Shawn Guo <shawn.guo@linaro.org>
Subject: Re: [alsa-devel] [PATCH v2 2/3] ASoC: dmaengine-pcm: Rename and
 deprecate snd_dmaengine_pcm_pointer
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On Mon, Jun 11, 2012 at 08:11:41PM +0200, Lars-Peter Clausen wrote:
> Currently the sound dmaengine pcm helper functions implement the pcm_pointer
> callback by trying to count the number of elapsed periods. This is done by
> advancing the stream position in the dmaengine callback by one period.
> Unfortunately there is no guarantee that the callback will be called for each
> elapsed period. It may be possible that under high system load it is only called
> once for multiple elapsed periods. This patch renames the current implementation
> and documents its shortcomings and that it should not be used anymore in new
> drivers.
> 
> The next patch will introduce a new snd_dmaengine_pcm_pointer which will be
> implemented based on querying the current stream position from the dma device.
> 
> Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
> 
Acked-by: Dong Aisheng <dong.aisheng@linaro.org>

> ---
> If you are maintaining a pcm driver which use the dmaengine pcm helper please
> check if you platform works with the new snd_dmaengine_pcm_pointer
> implementation which is added in the next patch (ux500 seems to be good
> candidate). And if it does send a follow-up patch to convert your platform to
> the new implementation. If it does not please try to fix or add residue
> reporting support to your dmaengine driver.
> 
Will try it after adding cyclic tx_status support for mxs/imx dma driver.

Regards
Dong Aisheng

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