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

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Message-Id: <20070611120034.f6d972de.akpm@linux-foundation.org>
Date:	Mon, 11 Jun 2007 12:00:34 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Pavel Machek <pavel@....cz>
Cc:	Christian Leber <christian@...er.de>,
	kernel list <linux-kernel@...r.kernel.org>
Subject: Re: beeping patch for debugging acpi sleep

On Sat, 9 Jun 2007 15:08:17 +0200
Pavel Machek <pavel@....cz> wrote:

> 
> 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?

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

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