linux-kernel - Re: [alsa-devel] [PATCH][2.6.31-rc5] ARM: OMAP: McBSP: Fix ASoC on OMAP1510 by fixing API of omap_mcbsp

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Date:	Fri, 7 Aug 2009 11:52:47 +0300
From:	Peter Ujfalusi <peter.ujfalusi@...ia.com>
To:	alsa-devel@...a-project.org
Cc:	ext Jarkko Nikula <jhnikula@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Janusz Krzysztofik <jkrzyszt@....icnet.pl>,
	Tony Lindgren <tony@...mide.com>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>
Subject: Re: [alsa-devel] [PATCH][2.6.31-rc5] ARM: OMAP: McBSP: Fix ASoC on OMAP1510 by fixing API of omap_mcbsp_start/stop

On Friday 07 August 2009 09:59:47 ext Jarkko Nikula wrote:
> Simultaneous audio playback and capture on OMAP1510 can cause that second
> stream is stalled if there is enough delay between startup of the audio
> streams.
>
> Current implementation of the omap_mcbsp_start is starting both transmitter
> and receiver at the same time and it is called only for firstly started
> audio stream from the OMAP McBSP based ASoC DAI driver.
>
> Since DMA request lines on OMAP1510 are edge sensitive, the DMA request is
> missed if there is no DMA transfer set up at that time when the first word
> after McBSP startup is transmitted. The problem hasn't noted before since
> later OMAPs are using level sensitive DMA request lines.
>
> Fix the problem by changing API of omap_mcbsp_start and omap_mcbsp_stop by
> allowing to start and stop individually McBSP transmitter and receiver
> logics. Then call those functions individually for both audio playback
> and capture streams. This ensures that DMA transfer is setup before
> transmitter or receiver is started.
>
> Thanks to Janusz Krzysztofik <jkrzyszt@....icnet.pl> for detailed problem
> analysis and Peter Ujfalusi <peter.ujfalusi@...ia.com> for info about DMA
> request line behavior differences between the OMAP generations.
>
> Reported-and-tested-by: Janusz Krzysztofik <jkrzyszt@....icnet.pl>
> Signed-off-by: Jarkko Nikula <jhnikula@...il.com>
> Cc: Mark Brown <broonie@...nsource.wolfsonmicro.com>
> Cc: Tony Lindgren <tony@...mide.com>
> ---
>  arch/arm/plat-omap/include/mach/mcbsp.h |    4 +-
>  arch/arm/plat-omap/mcbsp.c              |   50
> +++++++++++++++++++----------- sound/soc/omap/omap-mcbsp.c             |  
> 10 +++---
>  3 files changed, 39 insertions(+), 25 deletions(-)

Acked-by: Peter Ujfalusi <peter.ujfalusi@...ia.com>

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