[alsa-devel] channel swapping issue on OMAP3/TWL4030 is back

Russell King - ARM Linux linux at arm.linux.org.uk
Fri Mar 22 17:35:06 CET 2013

On Fri, Mar 22, 2013 at 02:04:42PM +0100, Peter Ujfalusi wrote:
> Russell: can we remove the tasklet use from dma-omap and start the DMA right
> away in omap_dma_issue_pending()? This is the only way to prevent channel
> swap when starting audio.

What I fear is that we may run up against having too many DMA channels
tied up to the peripherals.  I structured the driver in this way to
allow us to move the physical DMA channel allocation to that tasklet
when that becomes a problem.

Not only that but I was hoping to lift some more of this code out of
DMA engine drivers, so DMA engine drivers had even less code in them.

I guess we could keep the tasklet, but mark the audio DMA channels as
"pre-reserved" and arrange for pre-reserved channels to avoid the
tasklet, rather than throwing the tasklet out completely.

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