[alsa-devel] [PATCH] Fix PIT lockup on some chipsets when using the PC-Speaker

[Takashi Iwai]

At Mon, 3 Nov 2008 00:30:28 +0100,
Zoltan Devai wrote:
> 
> Hi,
> 
> There've been reports [1] about the sysem bell causing a hard lockup.
> My machine was affected as well: Any speaker output hung the machine
> completely, nothing in the logs, no magic sysrq, etc., looked like a
> hardware problem.
> Had a closer look on the issue, and it turned out that the pcspkr module is
> responsible. The cause is the bad setup of Timer 2 in the i8253 controller,
> which probably hangs the whole PIT controller.
> 
> Intel datasheets [2] state that the timer registers are in an undefined
> state after reset and they need to be programmed before enabling the
> timer. (And enabling without programming the frequency first doesn't
> make sense anyway).
> 
> I don't know which chipsets are affected (if not all), it also depends on
> the BIOS whether it initializes the timer (e.g. to beep when you start the
> machine).
> 
> The following patch solved the issue on my ICH6 notebook, couldn't
> test it with any others, but should be safe to apply.
> 
> I've also sent a patch to the linux-input list for the pcspkr module.
> 
> [1]
> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/146151
> https://bugs.launchpad.net/ubuntu/+bug/270790
> http://ubuntuforums.org/showthread.php?t=227693
> http://bugs.gentoo.org/show_bug.cgi?id=222583
> https://bugzilla.redhat.com/show_bug.cgi?id=454225
> 
> [2]
> http://www.intel.com/assets/pdf/datasheet/252516.pdf
> http://www.intel.com/assets/pdf/datasheet/301473.pdf
> http://www.intel.com/design/chipsets/datashts/29065503.pdf
> 
> ------------------
> 
> Fix PIT lockup on some chipsets when using the PC-Speaker.
> 
> Signed-off-by: Zoltan Devai <zdevai at gmail.com>

Looks good to me.  Applied now.
Thanks!

Takashi