linux-kernel - Re: i686 quirk for AMD Geode

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Message-ID: <20091113165730.0b9b2676@lxorguk.ukuu.org.uk>
Date:	Fri, 13 Nov 2009 16:57:30 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	lsorense@...lub.uwaterloo.ca (Lennart Sorensen)
Cc:	Pavel Machek <pavel@....cz>,
	Lennart Sorensen <lsorense@...lub.uwaterloo.ca>,
	"H. Peter Anvin" <hpa@...or.com>,
	Matteo Croce <technoboy85@...il.com>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org
Subject: Re: i686 quirk for AMD Geode

O> Calling memcpy_toio on the Geode SC1200 on anything larger than 1 byte
> causes the data to be delivered (at least on the PCI bus) reordered in
> that very consistent manner.

Sounds like you or your firmware have the caching and write combining
misconfigured.

> 
> The alignment doesn't affect it (I tested that).  Simply doing more than
> 1 byte at a time with memcpy_toio to the pci device messes up.

Which usually means some form of write gathering is enabled or something
thinks the device is write combining on the PCI bus. What does the PCI
bus and the RCRR MTRR set look like ?

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