Messages in this thread | | | From | Johannes Weiner <> | Subject | Re: Longstanding bug in ac97/intel8x0 resume/init | Date | Tue, 01 Jul 2008 17:12:02 +0200 |
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Hi,
Takashi Iwai <tiwai@suse.de> writes:
> At Tue, 01 Jul 2008 16:37:42 +0200, > Johannes Weiner wrote: >> >> Hi, >> >> Takashi Iwai <tiwai@suse.de> writes: >> >> > At 30 Jun 2008 20:58:03 +0200, >> > Mathieu Chouquet-Stringer wrote: >> >> >> >> Hey there, >> >> >> >> hannes@saeurebad.de (Johannes Weiner) writes: >> >> > Johannes Weiner <hannes@saeurebad.de> writes: >> >> > > my laptop has muted sound after resuming the soundcard (by >> >> > > s2ram/hibernation). The problem seems to be that the cached register >> >> > > values are not written back to the device properly. >> >> >> >> I've got the same exact issue on a Thinkpad T30: >> >> >> >> 0 [I82801CAICH3 ]: ICH - Intel 82801CA-ICH3 >> >> Intel 82801CA-ICH3 with AD1881A at irq 5 >> >> >> >> 00:1f.5 Multimedia audio controller: Intel Corporation 82801CA/CAM AC'97 Audio Controller (rev 02) >> > >> > Does this happen for both hibernation and S2RAM? >> > And, resetting the mixer repairs the mute state, right? >> > If yes, the problem appears independently from the codec chip. Hmm... >> >> Yes, happens in both cases here. >> >> The alsamixer shows the state of the channels before the suspension(!). > > Yes. The driver returns the cached values.
Okay.
>> If I change the channel state, the sound works again. No complete reset >> needed at all, I just have to increase/decrease the value a bit (for >> each affected channel). > > Just touching one mixer element?
What means `element' here? I have to touch MASTER and PCM in order to get some output again, at least ;)
>> >From my experiments with the code, I figured that the cached register >> values are not written back properly on resume. The cache is in the >> correct state but the hardware is not. This also explains the behaviour >> when changing the channels with alsamixer; the register cache is touched >> and written back (and this time, the value really gets through to the >> hardware). > > Right. > > snd_ac97_resume() has a check whether the write to MASTER register > succeeds, but its timeout is 100ms. Could you check whether this > check passes at resume or failed? I remember that some device > actually passed the test but didn't update the real hardware state. > If it failed on yours, we may simply extend the timeout, or make it > pending somehow. If the hardware fools us, however, it'd be toucher.
By experimentation I found that the writeback works with a two seconds delay before writeback. I can't remember if it was before or after the check. Another approach was to hammer down the value by writing and reading back in a loop until the hardware responded with the correct value.
I will redo the tests later and report back to you what helped.
Hannes
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