From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russell King - ARM Linux Subject: Re: [RFC 3/4] arm64: Do not call enable PCI resources when specify PCI_PROBE_ONLY Date: Wed, 24 Jun 2015 00:05:39 +0100 Message-ID: <20150623230539.GK7557@n2100.arm.linux.org.uk> References: <1411937610-22125-1-git-send-email-suravee.suthikulpanit@amd.com> <1411937610-22125-4-git-send-email-suravee.suthikulpanit@amd.com> <1435098868.3996.11.camel@kernel.crashing.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1435098868.3996.11.camel@kernel.crashing.org> Sender: linux-pci-owner@vger.kernel.org To: Benjamin Herrenschmidt Cc: Bjorn Helgaas , Mark Rutland , "devicetree@vger.kernel.org" , Jason Cooper , "linux-doc@vger.kernel.org" , Marc Zyngier , Will Deacon , Liviu Dudau , "linux-kernel@vger.kernel.org" , "linux-pci@vger.kernel.org" , Rob Herring , Suravee Suthikulpanit , Catalin Marinas , Thomas Gleixner , linux-arm List-Id: devicetree@vger.kernel.org On Wed, Jun 24, 2015 at 08:34:28AM +1000, Benjamin Herrenschmidt wrote: > On Mon, 2014-09-29 at 12:17 -0600, Bjorn Helgaas wrote: > > This seems like more than necessary, but I don't know all the history. > > In particular, I don't know why PCI_PROBE_ONLY should make a > > difference to things like claiming resources. > > It shouldn't ... we created that option on ppc originally to avoid > allocation/reallocation of resources. If they are bad, leave them bad, > but it was never a question of disabling all these other things. > > (Ok, the MRSS/MPS is debatable, but why not plumb the parent pointers > and why not claim ? That doesn't make sense to me). You could look back over the history of arch/arm/kernel/bios32.c and see that it was introduced by Will Deacon when he stripped out the ARM version in favour of the generic version, and was found to be necessary then. I think the question has to be asked (based upon what Ben's saying) and what's identified in these commits as a failure case (pci_enable_resource failing when PCI_PROBE_ONLY is enabled) - why is the PCI core creating per-device resources which do not have parents. I've no idea on that; the only ARM boxes I have use the kernel's PCI allocation, I don't have these boxes which want to use PCI_PROBE_ONLY so it's something I have zero knowledge of. -- FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up according to speedtest.net.