From: Matthew Wilcox <matthew@wil.cx>
To: Roland Dreier <rdreier@cisco.com>
Cc: "Michael S. Tsirkin" <mst@mellanox.co.il>,
linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org,
jeff@garzik.org, openib-general@openib.org,
linux-pci@atrey.karlin.mff.cuni.cz,
David Miller <davem@davemloft.net>
Subject: Re: Ordering between PCI config space writes and MMIO reads?
Date: Tue, 31 Oct 2006 19:58:11 +0000 [thread overview]
Message-ID: <20061031195811.GF26964@parisc-linux.org> (raw)
In-Reply-To: <ada8xiwtg81.fsf@cisco.com>
On Tue, Oct 31, 2006 at 11:53:02AM -0800, Roland Dreier wrote:
> > Here's what I don't understand: according to PCI rules, pci config read
> > can bypass pci config write (both are non-posted).
> > So why does doing it help flush the writes as the comment claims?
>
> No, I don't believe a read of a config register can pass a write of
> the same register. (Someone correct me if I'm wrong)
I don't see anything in the PCI spec which forbids it, but I would
expect that hardware designers don't actually do that in practice.
WARNING: multiple messages have this Message-ID (diff)
From: Matthew Wilcox <matthew@wil.cx>
To: Roland Dreier <rdreier@cisco.com>
Cc: "Michael S. Tsirkin" <mst@mellanox.co.il>,
linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org,
jeff@garzik.org, openib-general@openib.org,
linux-pci@atrey.karlin.mff.cuni.cz,
David Miller <davem@davemloft.net>
Subject: Re: Ordering between PCI config space writes and MMIO reads?
Date: Tue, 31 Oct 2006 12:58:11 -0700 [thread overview]
Message-ID: <20061031195811.GF26964@parisc-linux.org> (raw)
In-Reply-To: <ada8xiwtg81.fsf@cisco.com>
On Tue, Oct 31, 2006 at 11:53:02AM -0800, Roland Dreier wrote:
> > Here's what I don't understand: according to PCI rules, pci config read
> > can bypass pci config write (both are non-posted).
> > So why does doing it help flush the writes as the comment claims?
>
> No, I don't believe a read of a config register can pass a write of
> the same register. (Someone correct me if I'm wrong)
I don't see anything in the PCI spec which forbids it, but I would
expect that hardware designers don't actually do that in practice.
next prev parent reply other threads:[~2006-10-31 19:58 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-10-24 19:13 Ordering between PCI config space writes and MMIO reads? Roland Dreier
2006-10-24 19:13 ` Roland Dreier
2006-10-24 19:22 ` Jeff Garzik
2006-10-24 19:22 ` Jeff Garzik
2006-10-24 21:47 ` Matthew Wilcox
2006-10-24 21:47 ` Matthew Wilcox
2006-10-24 21:51 ` Roland Dreier
2006-10-24 21:51 ` Roland Dreier
2006-10-24 22:12 ` John Partridge
2006-10-24 22:12 ` John Partridge
2006-10-24 22:36 ` Matthew Wilcox
2006-10-24 22:36 ` Matthew Wilcox
2006-10-24 22:43 ` David Miller
2006-10-24 22:43 ` David Miller
2006-10-25 14:15 ` Roland Dreier
2006-10-25 14:15 ` Roland Dreier
2006-10-31 19:02 ` Roland Dreier
2006-10-31 19:02 ` Roland Dreier
2006-10-31 19:53 ` Michael S. Tsirkin
2006-10-31 19:53 ` Michael S. Tsirkin
2006-10-31 19:53 ` Roland Dreier
2006-10-31 19:53 ` Roland Dreier
2006-10-31 19:58 ` Matthew Wilcox [this message]
2006-10-31 19:58 ` Matthew Wilcox
2006-10-31 20:28 ` Michael S. Tsirkin
2006-10-31 20:28 ` Michael S. Tsirkin
2006-10-31 20:34 ` Richard B. Johnson
2006-10-31 20:34 ` Richard B. Johnson
2006-10-31 20:47 ` Matthew Wilcox
2006-10-31 20:47 ` Matthew Wilcox
2006-10-31 22:30 ` Roland Dreier
2006-10-31 22:30 ` Roland Dreier
2006-11-01 16:27 ` John Partridge
2006-11-01 16:27 ` John Partridge
2006-11-01 16:46 ` Matthew Wilcox
2006-11-01 16:46 ` Matthew Wilcox
2006-11-01 17:08 ` John Partridge
2006-11-01 17:08 ` John Partridge
2006-11-01 17:14 ` Matthew Wilcox
2006-11-01 17:14 ` Matthew Wilcox
2006-11-01 23:04 ` David Miller
2006-11-01 23:04 ` David Miller
2006-11-02 1:08 ` John Partridge
2006-11-02 1:08 ` John Partridge
2006-10-31 20:50 ` Michael S. Tsirkin
2006-10-31 20:50 ` Michael S. Tsirkin
2006-10-24 22:59 ` [openib-general] " Jason Gunthorpe
2006-10-24 22:59 ` Jason Gunthorpe
2006-10-25 14:04 ` Roland Dreier
2006-10-25 14:04 ` Roland Dreier
2006-10-24 23:09 ` Michael S. Tsirkin
2006-10-24 23:09 ` Michael S. Tsirkin
2006-10-24 23:27 ` Jack Steiner
2006-10-24 23:27 ` Jack Steiner
2006-10-25 14:05 ` Roland Dreier
2006-10-25 14:05 ` Roland Dreier
2006-11-02 3:05 ` Jeremy Higdon
2006-11-02 3:05 ` Jeremy Higdon
2006-10-24 21:01 ` [openib-general] " JWM
2006-10-24 21:01 ` JWM
2006-10-24 21:24 ` Alan Cox
2006-10-24 21:24 ` Alan Cox
2006-10-24 21:29 ` Roland Dreier
2006-10-24 21:29 ` Roland Dreier
2006-10-24 21:37 ` Jeff Garzik
2006-10-24 21:37 ` Jeff Garzik
2006-10-25 6:30 ` Grant Grundler
2006-10-25 6:30 ` Grant Grundler
2006-10-25 14:11 ` Roland Dreier
2006-10-25 14:11 ` Roland Dreier
2006-10-25 14:18 ` Matthew Wilcox
2006-10-25 14:18 ` Matthew Wilcox
2006-10-25 17:15 ` [openib-general] " Jason Gunthorpe
2006-10-25 17:15 ` Jason Gunthorpe
2006-10-25 18:22 ` Michael S. Tsirkin
2006-10-25 18:22 ` Michael S. Tsirkin
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