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

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Message-ID: <20071217212827.GB22828@elte.hu>
Date:	Mon, 17 Dec 2007 22:28:27 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	"David P. Reed" <dpreed@...d.com>
Cc:	Rene Herman <rene.herman@...il.com>,
	"H. Peter Anvin" <hpa@...or.com>, Paul Rolland <rol@...917.net>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	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.


* David P. Reed <dpreed@...d.com> wrote:

> Ingo -
>
> I finished testing the rolled up patch that you provided.  It seems to work 
> just fine.  Thank you for putting this all together and persevering in this 
> long and complex discussion. 
> Here are the results, on the offending laptop, using 2.6.24-rc5 plus that 
> one patch.
>
> First: booted with normal boot parameters (no io_delay=):
>
>    According to dmesg, 0xed is used.
>
>    hwclock ran fine, hundreds of times.
>    my shell script loop doing "cat /dev/nvram > /dev/null" ran fine, 
> several times.
>    Running Rene's "port 80" speed test ran fine once, then froze the system 
> hard.  (expected)
>
> Second: booted with io_delay=0x80, several tests, rebooting after freezes:
>
>    hwclock froze system hard.  (this is the problem that drove me to find 
> this bug).
>    my shell script loop froze system hard.
>
> Third: booted with io_delay=none:
>
>    hwclock ran fine, also hundreds of times.
>    my shell script loop ran fine several times.
>    Running rene's port80 test ran fine twice, froze system hard on third 
> try.
>
> Fourth: booted with io_delay=udelay:
>
>    hwclock ran fine, also hundreds of times.
>    my shell script loop ran fine several times.
>    Running Rene's port80 test ran fine, froze system hard on second try.
>
> Analysis:
>
>    patch works fine, and default to 0xed seems super conservative. I 
> will probably use the boot parameter io_delay=none, because I don't 
> seem to have any I/O
>    devices that require any delays - and this way I can find any that 
>    do.

great, and thanks for the extensive testing! I've added this line to the 
patch:

 Tested-by: "David P. Reed" <dpreed@...d.com>

if you dont mind.

	Ingo
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