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: <47638C8C.2090604@gmail.com>
Date:	Sat, 15 Dec 2007 09:13:00 +0100
From:	Rene Herman <rene.herman@...il.com>
To:	Paul Rolland <rol@...917.net>
CC:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	"H. Peter Anvin" <hpa@...or.com>, Pavel Machek <pavel@....cz>,
	Ingo Molnar <mingo@...e.hu>, "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>, rol@...be.net
Subject: Re: [PATCH] x86_64: fix problems due to use of "outb" to port 80
 on some AMD64x2 laptops, etc.

On 15-12-07 09:08, Paul Rolland wrote:
> Hello,
> 
> On Fri, 14 Dec 2007 23:29:55 +0000
> Alan Cox <alan@...rguk.ukuu.org.uk> wrote:
> 
>> On Fri, 14 Dec 2007 14:13:46 -0800
>> "H. Peter Anvin" <hpa@...or.com> wrote:
>>
>>> Pavel Machek wrote:
>>>> On Fri 2007-12-14 10:02:57, H. Peter Anvin wrote:
>>> How long will that take to boot on a 386?
>> Well the dumb approach to fix that would seem to be to initialise it to
>>
>> 	cpu->family   3 -> 50MHz 4 -> 300Mhz 5-> etc...
> 
> Just an idea : from what I've read, the problem (port 80 hanging) only occurs
> on 'modern' machines... So why not :
>  - use port 80 for old CPUs (PII, PIII) where it has never really been
>    a problem,
>  - use the cpu->family to do a best match for CPU freq
> thus we could avoid increasing boot time too much...

Yes, just posted a Patch-For-Comments that switches on the availability of a 
TSC (tsc_init sets tsc_disable also for !cpu_has_tsc) which would mean that 
only really old stuff would be using the outb still. A TSC is really all we 
need to have a sensible udelay().

Rene.
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