[alsa-devel] via_dmapos_patch

[Takashi Iwai]

At Wed, 29 Sep 2010 10:14:49 +0200,
David Henningsson wrote:
> 
> I'm researching a few bugs where the user claims position_fix=1 helps 
> the problem, but adding the quirk for that model surprisingly didn't. So 
> looking at the code, I concluded that the difference was 
> via_dmapos_patch, and that they all had via_dmapos_patch=1, and that 
> via_dmapos_patch=0 helped them solve the problem. Three out of five (not 
> all of them have reported back on via_dmapos_patch=0 yet) are VIA 
> controllers rev 10.
> 
> So we now have VIA controllers that need via_dmapos_patch=0.
> 
> I can think of a few approaches here:
> 
> 1) since position_fix=1 implicitly sets via_dmapos_patch to 0 (maybe 
> unintentionally), we should add a position_fix=3 meaning lpib + 
> via_dmapos_patch=1
> 
> 2) figure if something has changed recently (as in "within the last 
> year"...) that has made via_dmapos_patch=1 work worse than before
> 
> 3) figure out if there are several ATI/VIA controllers that actually 
> never wants the patch.
> 
> Any thoughts?

All sound as reasonable proposals.
The 1 is easy.  David, could you care to send a patch?

2 and 3 aren't trivial, but we can start by disabling via_dmapos
for recent revisions.  Since it can be controlled over a module
option by the fix 1, it'll be easier to check the regression.


thanks,

Takashi