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

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Date:	Mon, 17 Dec 2007 02:48:26 +0100
From:	Rene Herman <rene.herman@...il.com>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	Paul Rolland <rol@...917.net>, Alan Cox <alan@...rguk.ukuu.org.uk>,
	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>,
	rol@...be.net
Subject: Re: [PATCH] x86: provide a DMI based port 0x80 I/O delay override.

On 16-12-07 22:42, H. Peter Anvin wrote:

> It probably comes down to which version is bigger (you probably also 
> want to try uninlining.)

slow_down_io() sort of needs to stay inline due to the REALLY_SLOW_IO thing. 
That stuff could use a cleanup, but that would be a diferent patch.

>> Thanks for the heads up (also saw the SMBIOS update to this) but those 
>> don't seem to be a problem in fact. David Reed has been running with 
>> the simple udelay(2) version of this and reported no more hangs. He 
>> moreover reported no trouble after booting with "acpi=off" meaning 
>> that things seem to be fine pre-acpi which the boot code (and this 
>> io_delay_init) is. So I believe we get to ignore those.
> 
> Okay, so there is something inside ACPI which tickles this.  Which 
> brings further credibility that it's activating a debugging hack, 
> probably inside the SuperIO/system controller chip.
> 
> It would be interesting to know exactly which part of ACPI triggers 
> this.  I bet it is a reference to system controller namespace.

Do you expect a BIOS update to be able to fix it? If so, I guess any DMI 
hack should take BIOS version into account.

Rene.
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