[alsa-devel] [PATCH 2/2] ASoC: omap: Stop DMA re enabling in self linkage mode

Liam Girdwood lrg at slimlogic.co.uk
Tue Dec 7 16:17:34 CET 2010

On Tue, 2010-12-07 at 16:38 +0200, Peter Ujfalusi wrote:
> On Tuesday 07 December 2010 16:05:12 ext Mark Brown wrote:
> > On Tue, Dec 07, 2010 at 11:17:26AM +0200, Peter Ujfalusi wrote:
> > > I have not seen this happening on OMAP2/3, or at least I'm not aware of
> > > it. Is this problem OMAP4 only?
> > > Do you know if this happens on playback, capture or in both direction?
> > > Is it worth to do this workaround only on OMAP4?
> > 
> > Given that the patch should cause at most a single read from a register
> > when tearing down DMA if it's not required I'd guess it's safer to just
> > unconditionally enable the workaround on the off chance that it's just
> > reallly rare rather than not needed?
> Sure, it is a single read to a register, but generally I'm a bit nervous, when 
> we have a while loop without timeout counter.
> In theory we could have infinite loop, if the HW has a bad day...
> This could be safe on all OMAP platforms, but I think it has been only tested on 
> OMAP4.
> If this could happen, than IMHO it has to be handled by the omap_stop_dma, since 
> other drivers could be hit by the same problem (there might be ERRATA for it 
> already for OMAP4).

Afaik, this has also been tested on OMAP3. Not sure about OMAP2 and most
likely not tested on OMAP1.


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