From: Nathan Lynch <ntl@pobox.com>
To: David Gibson <david@gibson.dropbear.id.au>
Cc: linuxppc-dev@ozlabs.org, Paul Mackerras <paulus@samba.org>
Subject: Re: [RFC/PATCH] remove gratuitous reads from maple pci config space methods
Date: Wed, 8 Aug 2007 23:16:32 -0500 [thread overview]
Message-ID: <20070809041632.GA13921@localdomain> (raw)
In-Reply-To: <20070809030555.GA8261@localhost.localdomain>
David Gibson wrote:
> On Wed, Aug 08, 2007 at 07:50:44PM -0500, Nathan Lynch wrote:
> > The maple pci configuration space write methods read the written
> > location immediately after the write is performed, presumably in order
> > to flush the write. However, configuration space writes are not
> > allowed to be posted, making these reads gratuitous.
>
> It might be worth checking that there isn't a particular reason for
> these. Just because posting writes are forbidden doesn't mean a
> particular bridge won't screw it up...
Well, I had already checked with Ben, who wrote the code, and my
understanding is that the reads are intended to work around some
misbehaving Apple bridges, but that a sync after the write (implied by
releasing pci_lock in the generic pci code) should suffice for those.
next prev parent reply other threads:[~2007-08-09 4:16 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-08-09 0:50 [RFC/PATCH] remove gratuitous reads from maple pci config space methods Nathan Lynch
2007-08-09 0:55 ` Benjamin Herrenschmidt
2007-08-09 1:04 ` Nathan Lynch
2007-08-09 1:14 ` Benjamin Herrenschmidt
2007-08-09 20:03 ` Olof Johansson
2007-08-09 3:05 ` David Gibson
2007-08-09 4:16 ` Nathan Lynch [this message]
2007-08-09 4:18 ` David Gibson
2007-08-09 10:40 ` Segher Boessenkool
2007-08-09 21:24 ` Nathan Lynch
2007-08-10 17:58 ` Segher Boessenkool
2007-08-11 23:41 ` Benjamin Herrenschmidt
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