[Copy Rob] On Thu, May 06, 2021 at 11:52:45AM +0100, Lorenzo Pieralisi wrote: > On Tue, May 04, 2021 at 08:16:30AM +0300, Mike Rapoport wrote: > > On Mon, May 03, 2021 at 10:46:29PM +0800, Boqun Feng wrote: > > > Currently we retrieve the PCI domain number of the host bridge from the > > > bus sysdata (or pci_config_window if PCI_DOMAINS_GENERIC=y). Actually > > > we have the information at PCI host bridge probing time, and it makes > > > sense that we store it into pci_host_bridge. One benefit of doing so is > > > the requirement for supporting PCI on Hyper-V for ARM64, because the > > > host bridge of Hyper-V doesnt' have pci_config_window, whereas ARM64 is > > > a PCI_DOMAINS_GENERIC=y arch, so we cannot retrieve the PCI domain > > > number from pci_config_window on ARM64 Hyper-V guest. > > > > > > As the preparation for ARM64 Hyper-V PCI support, we introduce the > > > domain_nr in pci_host_bridge, and set it properly at probing time, then > > > for PCI_DOMAINS_GENERIC=y archs, bus domain numbers are set by the > > > bridge domain_nr. > > > > > > Signed-off-by: Boqun Feng <boqun.feng@xxxxxxxxx> > > > --- > > > arch/arm/kernel/bios32.c | 2 ++ > > > arch/arm/mach-dove/pcie.c | 2 ++ > > > arch/arm/mach-mv78xx0/pcie.c | 2 ++ > > > arch/arm/mach-orion5x/pci.c | 2 ++ > > > arch/arm64/kernel/pci.c | 3 +-- > > > arch/mips/pci/pci-legacy.c | 2 ++ > > > arch/mips/pci/pci-xtalk-bridge.c | 2 ++ > > > drivers/pci/controller/pci-ftpci100.c | 2 ++ > > > drivers/pci/controller/pci-mvebu.c | 2 ++ > > > drivers/pci/pci.c | 4 ++-- > > > drivers/pci/probe.c | 7 ++++++- > > > include/linux/pci.h | 11 ++++++++--- > > > 12 files changed, 33 insertions(+), 8 deletions(-) > > > > > > diff --git a/arch/arm/kernel/bios32.c b/arch/arm/kernel/bios32.c > > > index e7ef2b5bea9c..4942cd681e41 100644 > > > --- a/arch/arm/kernel/bios32.c > > > +++ b/arch/arm/kernel/bios32.c > > > @@ -471,6 +471,8 @@ static void pcibios_init_hw(struct device *parent, struct hw_pci *hw, > > > bridge->sysdata = sys; > > > bridge->busnr = sys->busnr; > > > bridge->ops = hw->ops; > > > + if (IS_ENABLED(CONFIG_PCI_DOMAINS_GENERIC)) > > > + bridge->domain_nr = pci_bus_find_domain_nr(sys, parent); > > > > > > ret = pci_scan_root_bus_bridge(bridge); > > > } > > > diff --git a/arch/arm/mach-dove/pcie.c b/arch/arm/mach-dove/pcie.c > > > index ee91ac6b5ebf..92eb8484b49b 100644 > > > --- a/arch/arm/mach-dove/pcie.c > > > +++ b/arch/arm/mach-dove/pcie.c > > > @@ -167,6 +167,8 @@ dove_pcie_scan_bus(int nr, struct pci_host_bridge *bridge) > > > bridge->sysdata = sys; > > > bridge->busnr = sys->busnr; > > > bridge->ops = &pcie_ops; > > > + if (IS_ENABLED(CONFIG_PCI_DOMAINS_GENERIC)) > > > + bridge->domain_nr = pci_bus_find_domain_nr(sys, NULL); > > > > The check for CONFIG_PCI_DOMAINS_GENERIC is excessive because there is a > > stub for pci_bus_find_domain_nr(). > > > > I'm not an expert in PCI, but maybe the repeated assignment of > > bridge->domain_nr can live in the generic code, say, in > > pci_scan_root_bus_bridge(). E.g. it will set the domain_nr when it is zero. > > > > > > > Yes, this churn should be avoided. We need a sentinel value to detect > whether the domain_nr is invalid (0 is a valid domain) so generic code > (ie pci_scan_root_bus_bridge() and friends) has to call generic > functions to get it (pci_bus_find_domain_nr()). > Agreed. Thank you all for the inputs. According to [1], "PCI Conventional" has at most 256 PCI bus segments and "PCI Express" has at most 65536 "PCI Segments Groups", so any value outside [0, 65536] can be used as a sentinel. I'm planning to use -1 like: #define PCI_DOMAIN_NR_NOT_SET (-1) (in pci_alloc_host_bridge()) bridge->domain_nr = PCI_DOMAIN_NR_NOT_SET; (in pci_register_host_bridge()) if (bridge->domain_nr == PCI_DOMAIN_NR_NOT_SET) bridge->domain_nr = pci_bus_find_domain_nr(...); Thoughts? Regards, Boqun [1]: https://wiki.osdev.org/PCI_Express > We can implement it as a flag or function pointer in the struct > pci_host_bridge, if the flag or function pointer is not set the > generic pci_bus_find_domain_nr() should be called. > > Lorenzo
