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

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Date:	Mon, 7 Jan 2008 23:25:14 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Bodo Eggert <7eggert@....de>
Cc:	"H. Peter Anvin" <hpa@...or.com>, 7eggert@....de,
	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.

> 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.

Alan
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