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Date: Fri, 7 Dec 2007 18:42:37 +0000
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Rene Herman <rene.herman@keyaccess.nl>
Cc: Andi Kleen <andi@firstfloor.org>, "David P. Reed" <dpreed@reed.com>,
       linux-kernel@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
       Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: RFC: outb 0x80 in inb_p, outb_p harmful on some modern AMD64
 with MCP51 laptops
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On Fri, 07 Dec 2007 19:45:25 +0100
Rene Herman <rene.herman@keyaccess.nl> wrote:

> On 07-12-07 18:19, Alan Cox wrote:
> 
> > On Fri, 7 Dec 2007 17:31:16 +0100
> > Andi Kleen <andi@firstfloor.org> wrote:
> > 
> >>> You don't need to. Port 0x80 historically is about 8uS so just udelay(8)
> >>> and make sure the initial default delay is conservative enough before the
> >> How would you make it conservative enough handling let's say a 6Ghz CPU
> >> that can execute multiple jumps per cycle?
> > 
> > Pick a sane worst case and go with it at boot. We don't have to be
> > accurate before we tune udelay - over long in uSecs isnt going to hurt,
> > and most post boot _p's can be replaced by udelay(8) now
> 
> Isn't 8 generally a bit overly long? I believe the norm is 1?

8uS is an ISA bus transaction.