From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bjorn Helgaas Subject: Re: [PATCH V2 5/9] PCI: Export pci_flags Date: Thu, 30 Nov 2017 12:42:24 -0600 Message-ID: <20171130184224.GA19640@bhelgaas-glaptop.roam.corp.google.com> References: <1511638333-22951-1-git-send-email-mmaddireddy@nvidia.com> <1511638333-22951-6-git-send-email-mmaddireddy@nvidia.com> <20171129170133.GC6469@bhelgaas-glaptop.roam.corp.google.com> <20171130102436.GB10349@red-moon> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20171130102436.GB10349@red-moon> Sender: linux-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Lorenzo Pieralisi Cc: Manikanta Maddireddy , thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, jonathanh-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org, robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, frowand.list-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, bhelgaas-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, rjw-LthD3rsA81gm4RdzfppkhA@public.gmane.org, tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org, vidyas-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org, kthota-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org, linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-pm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-tegra@vger.kernel.org On Thu, Nov 30, 2017 at 10:24:37AM +0000, Lorenzo Pieralisi wrote: > On Wed, Nov 29, 2017 at 11:01:33AM -0600, Bjorn Helgaas wrote: > > [+cc Lorenzo] > > > > On Sun, Nov 26, 2017 at 01:02:09AM +0530, Manikanta Maddireddy wrote: > > > pci_flags variable is used in inline functions in 'pci.h', Tegra PCIe > > > driver use one of these functions pci_add_flags() and includes 'pci.h'. > > > Export pci_flags to allow Tegra PCIe host controller driver to be > > > compiled as loadable kernel module. > > > > Here's the usage in tegra_pcie_probe(): > > > > pci_add_flags(PCI_REASSIGN_ALL_RSRC | PCI_REASSIGN_ALL_BUS); > > > > We've probably had this discussion before, but I don't know why Tegra > > needs PCI_REASSIGN_ALL_RSRC and PCI_REASSIGN_ALL_BUS. > > > > I would prefer to drop this usage of pci_add_flags() if possible. It > > seems to be just an arm/powerpc thing and I'm not convinced it's > > really necessary. > > It is hard to say if it is really necessary (because it depends > on firmware configuration - ie pci_scan_bridge()), that's the > problem. > > I suspect it can trigger regressions if we do not set it (since > it affects what pcibios_assign_all_busses() returns on eg arm/arm64). > > There are two things we can do: > > 1) Set it unconditionally in arch code (in a hook to be defined) > 2) We remove it on a per-host bridge basis and ask for testing > > I agree this may have trickled from host bridge to host bridge through > copy'n'paste and it is not based on any firmware assumtpion but I can't > say if it is really needed. My basic position is that if resources are not assigned correctly, the PCI core should automatically try to assign them, regardless of whether PCI_REASSIGN_ALL_RSRC or PCI_REASSIGN_ALL_BUS is set. If that doesn't work, I think there's something wrongin the PCI core and we should fix that. This might be an opportunity to try removing the use of pci_add_flags() and see what breaks. Bjorn From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.99]:57642 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750723AbdK3Sm1 (ORCPT ); Thu, 30 Nov 2017 13:42:27 -0500 Date: Thu, 30 Nov 2017 12:42:24 -0600 From: Bjorn Helgaas To: Lorenzo Pieralisi Cc: Manikanta Maddireddy , thierry.reding@gmail.com, jonathanh@nvidia.com, robh+dt@kernel.org, frowand.list@gmail.com, bhelgaas@google.com, rjw@rjwysocki.net, tglx@linutronix.de, vidyas@nvidia.com, kthota@nvidia.com, linux-tegra@vger.kernel.org, devicetree@vger.kernel.org, linux-pci@vger.kernel.org, linux-pm@vger.kernel.org Subject: Re: [PATCH V2 5/9] PCI: Export pci_flags Message-ID: <20171130184224.GA19640@bhelgaas-glaptop.roam.corp.google.com> References: <1511638333-22951-1-git-send-email-mmaddireddy@nvidia.com> <1511638333-22951-6-git-send-email-mmaddireddy@nvidia.com> <20171129170133.GC6469@bhelgaas-glaptop.roam.corp.google.com> <20171130102436.GB10349@red-moon> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20171130102436.GB10349@red-moon> Sender: linux-pci-owner@vger.kernel.org List-ID: On Thu, Nov 30, 2017 at 10:24:37AM +0000, Lorenzo Pieralisi wrote: > On Wed, Nov 29, 2017 at 11:01:33AM -0600, Bjorn Helgaas wrote: > > [+cc Lorenzo] > > > > On Sun, Nov 26, 2017 at 01:02:09AM +0530, Manikanta Maddireddy wrote: > > > pci_flags variable is used in inline functions in 'pci.h', Tegra PCIe > > > driver use one of these functions pci_add_flags() and includes 'pci.h'. > > > Export pci_flags to allow Tegra PCIe host controller driver to be > > > compiled as loadable kernel module. > > > > Here's the usage in tegra_pcie_probe(): > > > > pci_add_flags(PCI_REASSIGN_ALL_RSRC | PCI_REASSIGN_ALL_BUS); > > > > We've probably had this discussion before, but I don't know why Tegra > > needs PCI_REASSIGN_ALL_RSRC and PCI_REASSIGN_ALL_BUS. > > > > I would prefer to drop this usage of pci_add_flags() if possible. It > > seems to be just an arm/powerpc thing and I'm not convinced it's > > really necessary. > > It is hard to say if it is really necessary (because it depends > on firmware configuration - ie pci_scan_bridge()), that's the > problem. > > I suspect it can trigger regressions if we do not set it (since > it affects what pcibios_assign_all_busses() returns on eg arm/arm64). > > There are two things we can do: > > 1) Set it unconditionally in arch code (in a hook to be defined) > 2) We remove it on a per-host bridge basis and ask for testing > > I agree this may have trickled from host bridge to host bridge through > copy'n'paste and it is not based on any firmware assumtpion but I can't > say if it is really needed. My basic position is that if resources are not assigned correctly, the PCI core should automatically try to assign them, regardless of whether PCI_REASSIGN_ALL_RSRC or PCI_REASSIGN_ALL_BUS is set. If that doesn't work, I think there's something wrongin the PCI core and we should fix that. This might be an opportunity to try removing the use of pci_add_flags() and see what breaks. Bjorn