linux-kernel - Re: [PATCH] x86: provide a DMI based port 0x80 I/O delay override.

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Date:	Tue, 8 Jan 2008 14:17:49 +0100 (CET)
From:	Bodo Eggert <7eggert@....de>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
cc:	Bodo Eggert <7eggert@....de>, "H. Peter Anvin" <hpa@...or.com>,
	Christer Weinigel <christer@...nigel.se>,
	Ingo Molnar <mingo@...e.hu>, "David P. Reed" <dpreed@...d.com>,
	Rene Herman <rene.herman@...il.com>,
	Paul Rolland <rol@...917.net>, Pavel Machek <pavel@....cz>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	rol@...be.net
Subject: Re: [PATCH] x86: provide a DMI based port 0x80 I/O delay override.

On Mon, 7 Jan 2008, Alan Cox wrote:

> > But overclocking is not the problem for udelay, it would err to the safe 
> > side. The problem would be a BUS having < 8 MHz, and since the days of 
> > 80286, they are hard to find. IMO having an option to set the bus speed
> > for those systems should be enough.
> 
> If you get it wrong you risk data corruption. Not good, not clever, not
> appropriate. Basically the use of port 0x80 is the right thing to do for
> ISA devices and as 15 odd years of use has shown works reliably and
> solidly for ISA systems.

As long as there is no port 80 card or a similar device using it. If 
there is a port 80 card, ISA acess needing the delay does break, cause
the data corruption you fear and does cause this thread to be started.
Pest, Cholera ...

OTOH, maybe the 6-MHz-delay is the same as the 8-MHz-delay, and the kernel 
parameter is not needed.
-- 
Fun things to slip into your budget
A Romulan Cloaking device:
	The PHB won't know what it is but will be to chicken to ask
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