[alsa-devel] [PATCH] ALSA: hda - Disable runtime PM on LynxPoint(-LP) controllers

David Henningsson david.henningsson at canonical.com
Wed Nov 20 14:35:09 CET 2013

On 11/20/2013 02:32 PM, Takashi Iwai wrote:
> At Wed, 20 Nov 2013 13:05:23 +0100,
> Takashi Iwai wrote:
>> At Wed, 20 Nov 2013 09:54:42 +0100,
>> David Henningsson wrote:
>>> (Adding Mengdong to cc)
>>> On 11/19/2013 05:51 PM, Takashi Iwai wrote:
>>>> We got bug reports of the stalled HD-audio, typically after S3 or S4,
>>>> and it turned out that they seemed triggered by runtime PM on Lynx
>>>> Point and Lynx Point-LP controllers.  As there is no way to recover
>>>> properly from the stalled controller, it's safer to disable the
>>>> runtime PM support on these chips for now.
>>> Oh, this is a bit sad news. Have you talked to Intel about it?
>>> Anyway, I saw something similar a while ago, but never with access to
>>> the hardware, and then it was difficult to reproduce for the person on
>>> the other side. Nevertheless, when I read through the PM code I found
>>> that the GCTL register was sometimes accessed with readb (although it is
>>> a 32 bit register), so I wrote a patch for that, but the testing results
>>> of this patch were a bit inconclusive, so I never upstreamed it.
>>> Anyway, I'm attaching the draft patch. Do you think it could be related?
>> It didn't change the behavior although the change looks good.

It looks good indeed, but it's always scary to do subtle changes without
testing on all the 50+ controllers we support...do you think I should
submit a proper patch for it?

>> After a long debugging session in this morning, I finally nailed
>> down.  This was the fault in the sound driver after all, shamefully :)
>> The fix patch is below.
>> The code needs a bit clean up, and I have it, but will apply this for
>> 3.14.
>> Takashi
>> ===
>> From: Takashi Iwai <tiwai at suse.de>
>> Subject: [PATCH 1/2] ALSA: hda - Fix unbalanced runtime PM notification at
>>  resume
> BTW, it's marked as 1/2 just because of the clean up patch I mentioned
> above.  Only this one is needed for now.

Ok, thanks for the clarification, and glad you finally found it! And so
are you I guess :-)

David Henningsson, Canonical Ltd.

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