linux-kernel - Re: beeping patch for debugging acpi sleep

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Message-ID: <20070611212608.GB3917@elf.ucw.cz>
Date:	Mon, 11 Jun 2007 23:26:08 +0200
From:	Pavel Machek <pavel@....cz>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Christian Leber <christian@...er.de>,
	kernel list <linux-kernel@...r.kernel.org>
Subject: Re: beeping patch for debugging acpi sleep

Hi!

> > Starting beeper as soon as ACPI sleep returns is very useful in
> > debugging "apparently dead" machines. If it beeps at all, it makes
> > sense to start playing with CMOS tracer.
> > 
> > Signed-off-by: Pavel Machek <pavel@...e.cz>
> > 
> > diff --git a/arch/i386/kernel/acpi/wakeup.S b/arch/i386/kernel/acpi/wakeup.S
> > index b781b38..cbf136e 100644
> > --- a/arch/i386/kernel/acpi/wakeup.S
> > +++ b/arch/i386/kernel/acpi/wakeup.S
> > @@ -11,7 +11,22 @@ # Do we need to deal with A20? It is oka
> >  #
> >  # If physical address of wakeup_code is 0x12345, BIOS should call us with
> >  # cs = 0x1234, eip = 0x05
> > -# 
> > +#
> > +
> > +#define BEEP \
> > +	inb	$97, %al; 	\
> > +	outb	%al, $0x80; 	\
> > +	movb	$3, %al; 	\
> > +	outb	%al, $97; 	\
> > +	outb	%al, $0x80; 	\
> > +	movb	$-74, %al; 	\
> > +	outb	%al, $67; 	\
> > +	outb	%al, $0x80; 	\
> > +	movb	$-119, %al; 	\
> > +	outb	%al, $66; 	\
> > +	outb	%al, $0x80; 	\
> > +	movb	$15, %al; 	\
> > +	outb	%al, $66;
> >  
> >  ALIGN
> >  	.align	4096
> > @@ -20,6 +35,9 @@ wakeup_code:
> >  	wakeup_code_start = .
> >  	.code16
> >  
> > +# Uncomment this to make your computer start producing ugly noise as soon
> > +# as BIOS returns to this real-mode entry point.
> > +#	BEEP
> >   	movw	$0xb800, %ax
> >  	movw	%ax,%fs
> >  	movw	$0x0e00 + 'L', %fs:(0x10)
> > 
> 
> How does the beep get turned off again?

Typically, pcmcia beeps after resume, making it quiet. If not, echo ^G
does it.

> Should the BEEP line be uncommented (in -mm at least)?

It's too gross a hack, I'd say. It is only ever useful if machine is
completely dead after s2ram.
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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