[alsa-devel] [PATCH] Fix PIT lockup on some chipsets when using the PC-Speaker
tiwai at suse.de
Mon Nov 3 08:22:43 CET 2008
At Mon, 3 Nov 2008 00:30:28 +0100,
Zoltan Devai wrote:
> There've been reports  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  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
> 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.
> 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.
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