On Wed, Apr 11, 2012 at 9:34 AM, Jiang Liu <liuj97@xxxxxxxxx> wrote: > On 04/11/2012 08:05 PM, Kenji Kaneshige wrote: >> (2012/04/11 13:02), Bjorn Helgaas wrote: >>> On Tue, Apr 10, 2012 at 6:10 PM, Jiang Liu<liuj97@xxxxxxxxx> wrote: >>>> This patchset enhance pci_root driver to update MMCFG information when >>>> hot-plugging PCI root bridges. It applies to Yinghai's tree at >>>> git://git.kernel.org/pub/scm/linux/kernel/git/yinghai/linux-yinghai.git for-pci-root-bus-hotplug >>>> >>>> The second patch is based on Taku Izumi work with some enhancements to >>>> correctly handle PCI host bridges without _CBA method. >>> >>> I'm sorry I won't have time to really review these for a couple weeks. >>> >>> It always seemed wrong to me that we parse MCFG and set things up >>> before we even look at PNP0A03/PNP0A08 devices. It would make more >>> sense to me to have something in acpi_pci_root_add() to set up >>> MMCONFIG using _CBA if available, and falling back to parsing MCFG if >>> it's not. >> >> I think your idea could make the code (design) much cleaner. >> Do you have any other reason why you think "It always seemed >> wrong..."? The current scheme is just an ugly design. Does I need more reasons? :) > Yeah, that may lead to a cleaner design. > But there are still some special cases, such as: > 1) ACPI subsystem is disabled by kernel boot options, so we can't rely > on the ACPI pci_root driver to initialize the MMCFG. I don't think it's a requirement to make everything work with "acpi=off". On a system with ACPI, running with "acpi=off" is just a kludge and if things work at all, it's only because we're very lucky. > 2) Some PCI host bridges are not reported by the ACPI namespace. My partner > has observed a system which doesn't report the host bridges embedded in the > NHM-EX processors. I don't think it's a requirement for Linux to use PCI devices behind unreported host bridges. I'd like to pick a date and say "after BIOS date X, we will no longer blindly probe for these unreported host bridges." Bjorn -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
