linux-kernel - Re: snd-hda-intel prevents machine to power off

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Date:	Tue, 28 Oct 2008 17:51:30 +0100
From:	Takashi Iwai <tiwai@...e.de>
To:	"Luiz Fernando N. Capitulino" <lcapitulino@...driva.com.br>
Cc:	linux-kernel@...r.kernel.org, alsa-devel@...a-project.org
Subject: Re: snd-hda-intel prevents machine to power off

At Tue, 28 Oct 2008 14:19:16 -0200,
Luiz Fernando N. Capitulino wrote:
> 
> Em Tue, 28 Oct 2008 17:07:42 +0100
> Takashi Iwai <tiwai@...e.de> escreveu:
> 
> | >  Hi Takashi,
> | > 
> | >  If I have some process with the sound device opened in my eeepc
> | > (say KDE's kmix) and try to power off the machine, for example with:
> | > 
> | > # echo o > /proc/sysrq-trigger
> | > 
> | >  The machine will not power off.
> | 
> | At which point does it stop?
> | What shows alt-sysrq-t (or w) output?
> 
>  I'm wondering how to get that kind of output because everything
> is disabled at that point (display inclusive).

OK, then it's hard to see.
A good news is that it goes at least fairly end point, thus likely no
hanging task, etc.

> | >  But it does work if I remove the snd-hda-intel module before issuing
> | > the echo above.
> | > 
> | >  This problem seems to be pretty popular among distros, I could find
> | > it reported for Mandriva, Ubuntu and Fedora.
> | 
> | Hmm, I haven't heard of unfixed issues.
> 
>  Well, these are the tickets I've found:
> 
> https://bugzilla.redhat.com/show_bug.cgi?id=444115
> https://bugs.launchpad.net/ubuntu/+source/linux-source-2.6.22/+bug/126140
> https://qa.mandriva.com/show_bug.cgi?id=44752

Looking through the comments that the power-saving helps, the problem
may disappear even without disabling the pci device.  The power-saving
doesn't involve with pci_disable_device() or changing the power-state
of the controler.  So, at least, the problem is either in the codec
or the controller setup.

Suppose you already use the power-saving and it solves the shutdown
problem, could you set power_save_controller=0 option for
snd-hda-intel, and check whether the shutdown still works or not?
If the shutdown doesn't work with this option, it means that
azx_stop_chip() is what would be needed.

Anyway, I feel this is rather a BIOS issue, and not sure what is the
best way to fix in the driver itself...

Takashi
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