[alsa-devel] [PATCH] ALSA: pxa2xx: fix ac97 cold reset for pxa27x

[Robert Jarzmik]

Mike Dunn <mikedunn at newsguy.com> writes:

> Currently, ac97 reset is broken on PXA27x.  Through trial-and-error (the pxa270
> developer's manual is mostly incoherent on the topic of ac97 reset), I fixed it
> by setting the WARM_RST bit in the GCR register at the end of the cold reset,
> and then skipping the warm reset if the link is already up and running.
>
> It appears that setting the WARM_RST bit is a necessary final step during cold
> reset.  I think that the PXA25x and PXA3xx may currently be working correctly
> because WARM_RST is set within the warm reset routine, and the codec drivers
> always follow a cold reset with a warm reset during their initialization. so
> this combination effectively completes a cold reset.  This doesn't work on the
> PXA27x because its warm reset routine contains additional code for working
> around a hardware bug in the warm reset sequence, which causes the reset
> sequence to fail.  I only have a PXA27x platform for testing, so this patch only
> affects the PXA27x.

Hi Mike,

I'm glad you take over that burden too :)
If you've tested that and if it work, that's great news. I'll test it also to
crosscheck.

This topic was discussed several years ago here :
http://www.spinics.net/lists/alsa-devel/msg12327.html

I think Mark has a much better view on the silicon defect, he will be of much
more help than me.

Cheers.

--
Robert