linux-kernel - Re: Ordering between PCI config space writes and MMIO reads?

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Date:	Tue, 24 Oct 2006 22:24:23 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Roland Dreier <rdreier@...co.com>
Cc:	linux-pci@...ey.karlin.mff.cuni.cz, linux-ia64@...r.kernel.org,
	linux-kernel@...r.kernel.org, openib-general@...nib.org,
	John Partridge <johnip@....com>
Subject: Re: Ordering between PCI config space writes and MMIO reads?

Ar Maw, 2006-10-24 am 12:13 -0700, ysgrifennodd Roland Dreier:
>  1) Is this something that should be fixed in the driver?  The PCI
>     spec allows MMIO cycles to start before an earlier config cycle
>     completed, but do we want to expose this fact to drivers?  Would
>     it be better for ia64 to use some sort of barrier to make sure
>     pci_write_config_xxx() is strongly ordered with MMIO?

It is good to be conservative in this area. Some AMD chipsets at least
had ordering problems with some configurations in the K7 era.


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