linux-kernel - Re: [PATCH v3 02/15] dmaengine: omap: Add support for pause/resume in cyclic dma mode

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Message-ID: <20120918082843.GD12445@n2100.arm.linux.org.uk>
Date:	Tue, 18 Sep 2012 09:28:44 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Vinod Koul <vinod.koul@...ux.intel.com>
Cc:	Peter Ujfalusi <peter.ujfalusi@...com>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Liam Girdwood <lrg@...com>, Tony Lindgren <tony@...mide.com>,
	Dan Williams <djbw@...com>,
	Jarkko Nikula <jarkko.nikula@...mer.com>,
	alsa-devel@...a-project.org, linux-omap@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Janusz Krzysztofik <jkrzyszt@....icnet.pl>,
	Ricardo Neri <ricardo.neri@...com>,
	Lars-Peter Clausen <lars@...afoo.de>
Subject: Re: [PATCH v3 02/15] dmaengine: omap: Add support for pause/resume
	in cyclic dma mode

On Mon, Sep 17, 2012 at 08:43:57AM +0530, Vinod Koul wrote:
> On Fri, 2012-09-14 at 15:05 +0300, Peter Ujfalusi wrote:
> > -       /* FIXME: not supported by platform private API */
> > -       return -EINVAL;
> > +       /* Pause/Resume only allowed with cyclic mode */
> > +       if (!c->cyclic)
> > +               return -EINVAL; 
> This is not a dma restriction right?

This is needed because this is not a real "pause" - it is a stop, which
causes the contents of the DMA engine's FIFOs to be discarded - which
means a subsequent resume will loose data.
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