linux-kernel - Re: [PATCH] x86_64: fix problems due to use of "outb" to port 80 on some AMD64x2 laptops, etc.

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Message-ID: <4762CA33.4080202@keyaccess.nl>
Date:	Fri, 14 Dec 2007 19:23:47 +0100
From:	Rene Herman <rene.herman@...il.com>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	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>,
	Pavel Machek <pavel@....cz>
Subject: Re: [PATCH] x86_64: fix problems due to use of "outb" to port 80
 on some AMD64x2 laptops, etc.

On 14-12-07 19:02, H. Peter Anvin wrote:

> I believe this will suffer from the issue that was raised: this will use
> udelay() long before loop calibration (and no, we can't just "be 
> conservative" since there is no "conservative" value we can use.)
> 
> Worse, I suspect that at least the PIT, which may need to be used for 
> udelay calibration, is one of the devices that may be affected.  I have 
> seen the Verilog for a contemporary chipset, and it can only access the 
> PIT once per microsecond -- this actually has to do with the definition 
> of the PIT; some of the PIT operations are ill-defined if allowed at a 
> higher frequency than the PIT clock.

Was reported before indeed:

http://linux.derkeiler.com/Mailing-Lists/Kernel/2003-09/5764.html

Rene.

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