linux-kernel - Re: RFC: outb 0x80 in inb_p, outb_p harmful on some modern AMD64 with MCP51 laptops

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Message-ID: <20071209222928.3f7b63a4@the-village.bc.nu>
Date:	Sun, 9 Dec 2007 22:29:28 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Pavel Machek <pavel@....cz>
Cc:	Andi Kleen <andi@...stfloor.org>,
	"David P. Reed" <dpreed@...d.com>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: RFC: outb 0x80 in inb_p, outb_p harmful on some modern AMD64
 with MCP51 laptops

On Sun, 9 Dec 2007 22:25:13 +0100
Pavel Machek <pavel@....cz> wrote:

> On Sun 2007-12-09 17:59:08, Andi Kleen wrote:
> > > I mean, we expect 8usec delay -- historical ISA timing -- but when
> > > _PCI_ card with leds is inserted, it is likely to be faster than old
> > > ISA, right?
> > 
> > Yes, i guess switching to udelay at least on newer systems would
> > be a good idea.  I'm not quite sure about systems without TSC though.
> 
> Something like this? (Warning, will not probably even compile on
> x86-64, I do not have 64-bit compiler near me).

You need to stick in a bug trap to verify that the udelay is not called
before the cpu timer has been set up.
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