From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: Peter Ujfalusi <peter.ujfalusi@ti.com>
Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>,
Liam Girdwood <lrg@ti.com>, Tony Lindgren <tony@atomide.com>,
Vinod Koul <vinod.koul@intel.com>, Dan Williams <djbw@fb.com>,
Jarkko Nikula <jarkko.nikula@bitmer.com>,
alsa-devel@alsa-project.org, linux-omap@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org,
Janusz Krzysztofik <jkrzyszt@tis.icnet.pl>,
Ricardo Neri <ricardo.neri@ti.com>
Subject: Re: [PATCH 11/11] ASoC: omap-pcm: Convert to use dmaengine
Date: Wed, 12 Sep 2012 13:00:28 +0100 [thread overview]
Message-ID: <20120912120028.GC28448@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <1347450427-27627-12-git-send-email-peter.ujfalusi@ti.com>
On Wed, Sep 12, 2012 at 02:47:07PM +0300, Peter Ujfalusi wrote:
> 2. Pause/Resume
> OMAP DMA engine backend does not support pausing and resuming
> an in-progress transfer. It is unclear from the specs what
> effect clearing the enable bit has on the DMA position of a
> destination synchronized transfer, and whether the transfer
> can be restarted from the exact point that it was paused (or
> whether the data in the FIFO read from memory is simply
> discarded.)
It's worth noting that this comment (which was in my original patch)
is there to spark _comment_ and _discussion_ and should not make its
way into the final version of these patches.
Given that suspend/resume is important on OMAP platforms, it's something
that needs to be resolved - in a way that complies with what ALSA expects.
I do not believe that the way the existing drivers do this is compliant
as the manuals imply that stopping memory->peripheral transfers results
in data being discarded from the DMA's FIFOs. As I understand it, ALSA
requires no data to be discarded.
As we have no way to know how much data may be discarded from the DMA
FIFO...
next prev parent reply other threads:[~2012-09-12 12:02 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-12 11:46 [PATCH 00/11] ASoC: OMAP: Convert to use dmaengine Peter Ujfalusi
2012-09-12 11:46 ` [PATCH 01/11] dmaengine: omap: Support for element mode in cyclic DMA Peter Ujfalusi
2012-09-12 11:46 ` [PATCH 02/11] ASoC: omap-mcbsp: Use sDMA packet mode instead of frame mode Peter Ujfalusi
2012-09-12 11:46 ` [PATCH 03/11] ASoC: omap-pcm: Select sDMA synchronization based on packet_size Peter Ujfalusi
2012-09-12 11:47 ` [PATCH 04/11] ASoC: OMAP: Remove sync_mode from omap_pcm_dma_data struct Peter Ujfalusi
2012-09-12 11:47 ` [PATCH 05/11] ASoC: omap-pcm: Prepare to configure the DMA data_type based on stream properties Peter Ujfalusi
2012-09-12 11:47 ` [PATCH 06/11] ARM: OMAP4: hwmod_data: Add resource names to McPDM memory ranges Peter Ujfalusi
2012-09-12 11:47 ` [PATCH 07/11] ASoC: omap-mcpdm: Use platform_get_resource_* to get resources Peter Ujfalusi
2012-09-12 11:47 ` [PATCH 08/11] ASoC: OMAP: mcbsp, mcpdm, dmic: Let omap-pcm to pick the dma_type Peter Ujfalusi
2012-09-12 11:47 ` [PATCH 09/11] ASoC: omap-pcm, omap-hdmi: Change the use of omap_pcm_dma_data->data_type Peter Ujfalusi
2012-09-12 11:47 ` [PATCH 10/11] ASoC: OMAP: mcbsp, mcpdm, dmic, hdmi: Set dma_data at startup time Peter Ujfalusi
2012-09-12 11:47 ` [PATCH 11/11] ASoC: omap-pcm: Convert to use dmaengine Peter Ujfalusi
2012-09-12 12:00 ` Russell King - ARM Linux [this message]
2012-09-12 12:53 ` Peter Ujfalusi
2012-09-12 14:35 ` Peter Ujfalusi
2012-09-12 14:05 ` [alsa-devel] " Takashi Iwai
2012-09-13 8:11 ` [PATCH 00/11] ASoC: OMAP: " Mark Brown
2012-09-13 9:20 ` Peter Ujfalusi
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