[alsa-devel] via_dmapos_patch

[David Henningsson]

On 2010-09-30 08:58, Takashi Iwai wrote:
> 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'm cc:ing Joseph here. You were the one writing via_dmapos_patch 
originally, could you confirm the suspicion that VIA controller rev 10 
(and possibly more) actually should have via_dmapos_patch turned off?

>>
>> 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?'

Something like this (untested)?

> 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.

-- 
David Henningsson, Canonical Ltd.
http://launchpad.net/~diwic
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