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

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Message-ID: <4766E765.4080006@zytor.com>
Date:	Mon, 17 Dec 2007 13:17:25 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	"David P. Reed" <dpreed@...d.com>
CC:	Rene Herman <rene.herman@...il.com>, Ingo Molnar <mingo@...e.hu>,
	Paul Rolland <rol@...917.net>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Pavel Machek <pavel@....cz>,
	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.

David P. Reed wrote:
> 
> Note that I can run the port 80 test once, the second time I get the 
> hard freeze.  I didn't try writing to port 70 from userspace - that 
> one's dangerous, but the reading of it was included for a timing typical 
> of a chipset supported device.  These are all pretty consistent.
> 
> I find the "read" timing from 0x80 verrrrry interesting.  The write 
> timeing is also interesting, being faster than an unused port.
> 

Once again: reading from port 0x80 goes to the DMA page device.

	-hpa
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