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

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Message-ID: <20071230212820.0d53f389@the-village.bc.nu>
Date:	Sun, 30 Dec 2007 21:28:20 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Rene Herman <rene.herman@...access.nl>, dpreed@...d.com,
	Islam Amer <pharon@...il.com>, hpa@...or.com,
	Pavel Machek <pavel@....cz>, Ingo Molnar <mingo@...hat.com>,
	Andi Kleen <andi@...stfloor.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86: provide a DMI based port 0x80 I/O delay override

> fact even io_delay=udelay would be wrong because any problem will be 
> less clearly triggerable and thus less bisectable/debuggable.

And if this eats someones disk because you drive the hardware out of spec
you are going to sit there and tell them to bisect it ? Lovely. 

Ingo - put the christmas wine away and have a coffee. Now think first.
You won't bisect obscure timing triggered problems, and the _p users are
almost all for hardware where performance doesn't matter one iota (eg
CMOS).

This isn't even all down to the chipset internal logic - several of my
boxes have external CMOS NVRAM/RTC chips which are probably the same
design (if a little smaller) as ten years ago.

io_delay = none is exactly the same thing as CPU overclocking. Hard to
debug, unpredictable and stupid.

Alan
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