linux-kernel - Re: Flushing writes to PCI devices

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Message-Id: <1158864356.11109.171.camel@localhost.localdomain>
Date:	Thu, 21 Sep 2006 19:45:56 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	"Bryan O'Sullivan" <bos@...pentine.com>
Cc:	Bill Waddington <william.waddington@...zmo.com>,
	linux-kernel@...r.kernel.org
Subject: Re: Flushing writes to PCI devices

Ar Iau, 2006-09-21 am 11:14 -0700, ysgrifennodd Bryan O'Sullivan:
> Yes.  If your device requires that writes to some locations in MMIO
> space be performed in a specific order, you must explicitly do this in
> your driver.  Intel CPUs will flush posted writes out of order, for
> example.

According to the docs I have here if the pci target area is
prefetchable/postwritable or has MTRRs set specifically to do this (eg
video ram).

There is no ordering guarantee between PCI and main memory however.

Alan

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