linux-kernel - Re: [PATCH] x86_64: fix problems due to use of "outb" to port 80 on some AMD64x2 laptops, etc.

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Message-ID: <20071215142929.5462b329@the-village.bc.nu>
Date:	Sat, 15 Dec 2007 14:29:29 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Rene Herman <rene.herman@...il.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"David P. Reed" <dpreed@...d.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Rene Herman <rene.herman@...access.nl>,
	Pavel Machek <pavel@....cz>
Subject: Re: [PATCH] x86_64: fix problems due to use of "outb" to port 80 on
 some AMD64x2 laptops, etc.

On Sat, 15 Dec 2007 14:27:25 +0100
Ingo Molnar <mingo@...e.hu> wrote:

> 
> * Rene Herman <rene.herman@...il.com> wrote:
> 
> > The issue is -- how do you safely replace the outb pre-loops_per_jiffy 
> > calibration? I'm currently running with the attached hack (not 
> > submitted, only for 32-bit and discussion) the idea of which might be 
> > the best we can do?
> 
> how about doing a known-NOP chipset cycle? For example:
> 
>   inb(PIC_SLAVE_IMR)

It needs tobe a different chip to the main one (or macrocell anyway) - so
PIC for PIT and vice versa. However since we know 0x80 works for
everything on the planet but this one specifies of laptop which seems to
need a firmware update its a very high risk approach.

Alan
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