From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:50139 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757138Ab1KOS0f (ORCPT ); Tue, 15 Nov 2011 13:26:35 -0500 Message-ID: <4EC2AE9A.1030208@redhat.com> Date: Tue, 15 Nov 2011 13:25:30 -0500 From: Prarit Bhargava MIME-Version: 1.0 To: Bjorn Helgaas CC: Rolf Eike Beer , Matthew Wilcox , Don Dutile , James Paradis , linux-pci@vger.kernel.org, mstowe@redhat.com, jbarnes@virtuousgeek.org Subject: Re: [PATCH] pci: Workaround Stratus broken PCIE hierarchy References: <4EBD73C8.8070407@redhat.com> <4EBD8714.30401@redhat.com> <4EC12962.2040105@redhat.com> <20111114181418.GE4387@parisc-linux.org> <4EC28B93.1060101@redhat.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-pci-owner@vger.kernel.org List-ID: Bjorn, > > Is this problem a regression? If so, what commit caused it? > f07852d6442, which introduced only_one_child()? That's a tough question to answer. AFAICT the broken (HARDWARE broken) Stratus systems only enumerated properly by chance. Did they work prior to f07852d6? From what jparadis told me, yes. Is it a regression? ... depends on how you look at it. > > Does Windows work on this system? I don't know. jparadis? Any clue? > > Is this something that could be fixed by a firmware upgrade? If so, > is there a Stratus/NEC bug report? Hmmm, the idea of a FW upgrade somehow fixing this never occurred to me. jparadis? Is that possible? > > Is there a Red Hat bugzilla URL you could include? Only happens upstream. > > What bad things would happen if we just turned on this > Stratus-specific behavior all the time on all systems? It looks like > f07852d6442 is basically an optimization that makes pci_scan_slot() > faster, so I assume one effect would be to slow down PCI enumeration > for everybody. By how much? Not a huge amount -- estimated lt 0.5 seconds on this Stratus system. As for other systems, it obviously depends on how complicated the PCIE hierarchy is. P.