From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jesse Barnes Subject: Re: [PATCH] x86/pci: do assign root bus res if _CRS is used Date: Mon, 27 Apr 2009 12:53:42 -0700 Message-ID: <20090427125342.7ec0e116@hobbes> References: <49ED22EC.2040204@kernel.org> <200904271344.04099.bjorn.helgaas@hp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <200904271344.04099.bjorn.helgaas@hp.com> Sender: linux-kernel-owner@vger.kernel.org To: Bjorn Helgaas Cc: Yinghai Lu , Ingo Molnar , "H. Peter Anvin" , Thomas Gleixner , "linux-kernel@vger.kernel.org" , linux-pci@vger.kernel.org, Gary Hade , Alex Chiang , linux-acpi@vger.kernel.org, Matthew Wilcox List-Id: linux-acpi@vger.kernel.org On Mon, 27 Apr 2009 13:44:01 -0600 Bjorn Helgaas wrote: > On Monday 20 April 2009 07:35:40 pm Yinghai Lu wrote: > > it wil be overwriten later if _CRS is used, so don't bother to set > > it. > > > > [ Impact: cleanup ] > > > > Signed-off-by: Yinghai Lu > > > > --- > > arch/x86/pci/amd_bus.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > Index: linux-2.6/arch/x86/pci/amd_bus.c > > =================================================================== > > --- linux-2.6.orig/arch/x86/pci/amd_bus.c > > +++ linux-2.6/arch/x86/pci/amd_bus.c > > @@ -100,6 +100,10 @@ void x86_pci_root_bus_res_quirks(struct > > int j; > > struct pci_root_info *info; > > > > + /* don't go for it if _CRS is used */ > > + if (pci_probe & PCI_USE__CRS) > > + return; > > + > > /* if only one root bus, don't need to anything */ > > if (pci_root_num < 2) > > return; > > This isn't a comment on this patch per se. > > I am concerned about the fact that "pci=use_crs" is not the default. > From the changelog of 62f420f8282, it sounds like you have to boot an > IBM x3850 with "pci=use_crs" to make hot-plug work, even though ACPI > tells us everything we need to know. That's backwards. > > We shouldn't need an option to tell Linux that the firmware is > trustworthy. We should have an option to *ignore* it for the times > when we trip over something broken and haven't figured out a way to > work around it yet. Well, we could try using _CRS by default, but like many things ACPI we can probably only trust firmwares after a certain date (i.e. the date when Windows started relying on the data being correct in order to boot). Do we have a good cutoff for that? Or should we try generally enabling it early in 2.6.31 to see what happens? -- Jesse Barnes, Intel Open Source Technology Center