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

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Date:	Mon, 17 Dec 2007 22:56:59 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Rene Herman <rene.herman@...il.com>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	"David P. Reed" <dpreed@...d.com>,
	"H. Peter Anvin" <hpa@...or.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.


* Rene Herman <rene.herman@...il.com> wrote:

>>> Signed-off-by: Rene Herman <rene.herman@...il.com>
>>
>> hm, i see this as a step backwards from the pretty flexible patch 
>> that David already tested. (and which also passed a few hundred 
>> bootup tests on my x86 test-grid)
>
> Please see Alan's comment that udelay (and none) shouldn't yet be 
> provided as a choice. It opens race windows in drivers even when it 
> works in practice on most setups. The version with "udelay" and "none" 
> is not minimal, not low risk and certainly not .24 material.

huh? By default we still use port 0x80. Any udelay is non-default and 
needs the user to explicitly switch to it. But it enables us to debug 
any suspected drivers by asking testers to: "please try this driver with 
io_delay=udelay, does it still work fine?". So those extra options are 
quite sensible. If you have any real technical arguments against that 
then please let us know.

	Ingo
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