From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Thu, 9 Aug 2007 14:18:03 +1000 From: David Gibson To: Nathan Lynch Subject: Re: [RFC/PATCH] remove gratuitous reads from maple pci config space methods Message-ID: <20070809041803.GG8261@localhost.localdomain> References: <20070809005044.GD10114@localdomain> <20070809030555.GA8261@localhost.localdomain> <20070809041632.GA13921@localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20070809041632.GA13921@localdomain> Cc: linuxppc-dev@ozlabs.org, Paul Mackerras List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, Aug 08, 2007 at 11:16:32PM -0500, Nathan Lynch wrote: > 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. Ah, ok then. -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson