Message-ID: <47659BAF.8030304@zytor.com>
Date: Sun, 16 Dec 2007 13:42:07 -0800
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Rene Herman <rene.herman@gmail.com>
CC: Paul Rolland <rol@as2917.net>, Alan Cox <alan@lxorguk.ukuu.org.uk>,
       Pavel Machek <pavel@ucw.cz>, Ingo Molnar <mingo@elte.hu>,
       "David P. Reed" <dpreed@reed.com>, Thomas Gleixner <tglx@linutronix.de>,
       linux-kernel@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
       rol@witbe.net
Subject: Re: [PATCH] x86: provide a DMI based port 0x80 I/O delay override.
References: <469578CD.3080609@reed.com>	<1184216528.12353.203.camel@chaos>	<1184218962.12353.209.camel@chaos>	<46964352.7040301@reed.com>	<1184253339.12353.223.camel@chaos>	<469697C6.50903@reed.com>	<1184274754.12353.254.camel@chaos>	<4761F193.7090400@reed.com>	<20071214131502.GA14359@elte.hu>	<4762C551.5070003@zytor.com>	<20071214210652.GB28793@elf.ucw.cz>	<4763001A.1070102@zytor.com>	<20071214232955.545ab809@the-village.bc.nu> <20071215080831.404cdb32@tux.DEF.witbe.net> <47638C8C.2090604@gmail.com> <476438B4.2020600@zytor.com> <476462BE.3030701@gmail.com> <4764687D.6080609@zytor.com> <476524DB.7020806@gmail.com>
In-Reply-To: <476524DB.7020806@gmail.com>
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Rene Herman wrote:
> 
> Well, I suppose. With stuff inline, constantly reloading dx also bloats 
> things up a bit but yes, out of line who cares. Do you think this 
> version is better?
> 

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

>> In the boot code, io_delay() is used to slow down accesses to the KBC, 
>> interrupt controller, INT13h logic, and the NMI gate, and to provide a 
>> fixed delay during A20 stabilization.
> 
> 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.

	-hpa
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