On Tuesday 26 July 2022 21:02:22 Michael Ellerman wrote: > Pali Rohár <pali@xxxxxxxxxx> writes: > > On Wednesday 06 July 2022 12:43:08 Pali Rohár wrote: > >> By default on PPC32 are PCI bus numbers unique across all PCI domains. > >> So system could have only 256 PCI buses independently of available > >> PCI domains. > >> > >> This is due to filling DT property pci-OF-bus-map which does not reflect > >> multi-domain setup. > >> > >> On all powerpc platforms except chrp and powermac there is no DT property > >> pci-OF-bus-map anymore and therefore it is possible on non-chrp/powermac > >> platforms to avoid this limitation of maximal number of 256 PCI buses in > >> system even on multi-domain setup. > >> > >> But avoiding this limitation would mean that all PCI and PCIe devices would > >> be present on completely different BDF addresses as every PCI domain starts > >> numbering PCI bueses from zero (instead of the last bus number of previous > >> enumerated PCI domain). Such change could break existing software which > >> expects fixed PCI bus numbers. > >> > >> So add a new config option CONFIG_PPC_PCI_BUS_NUM_DOMAIN_DEPENDENT which > >> enables this change. By default it is disabled. It cause that initial value > >> of hose->first_busno is zero. > >> > >> Signed-off-by: Pali Rohár <pali@xxxxxxxxxx> > >> --- > >> arch/powerpc/Kconfig | 11 +++++++++++ > >> arch/powerpc/kernel/pci_32.c | 6 ++++++ > >> 2 files changed, 17 insertions(+) > >> > >> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig > >> index be68c1f02b79..f66084bc1dfe 100644 > >> --- a/arch/powerpc/Kconfig > >> +++ b/arch/powerpc/Kconfig > >> @@ -370,6 +370,17 @@ config PPC_DCR > >> depends on PPC_DCR_NATIVE || PPC_DCR_MMIO > >> default y > >> > >> +config PPC_PCI_BUS_NUM_DOMAIN_DEPENDENT > >> + depends on PPC32 > >> + depends on !PPC_PMAC && !PPC_CHRP > >> + bool "Assign PCI bus numbers from zero individually for each PCI domain" > >> + help > >> + By default on PPC32 were PCI bus numbers unique across all PCI domains. > >> + So system could have only 256 PCI buses independently of available > >> + PCI domains. When this option is enabled then PCI bus numbers are > >> + PCI domain dependent and each PCI controller on own domain can have > >> + 256 PCI buses, like it is on other Linux architectures. > >> + > > > > What do you think, would it be possible to set default value of this > > option to enabled? > > My preference would be to not have the option at all, just make it the > default behaviour. Every new CONFIG option adds more combinations that > need testing, or more likely don't get well tested. > > But I don't have a good feel for what could break if we turn it on, so > honestly I don't really know. > > Also I do most of my 32-bit testing on pmacs, which are not affected by > the change. It is because this change is incompatible with deprecated pci-OF-bus-map which pmac uses. I do not have any pmac box for testing or development, so I let this part as is. If one day pci-OF-bus-map would be possible to disable on pmac then this pci bus number change can be enabled also for pmac. > So I'll probably take the series as-is, and then we can do some more > widespread testing and possibly flip the default to enabled, and then > maybe remove the option entirely in future. > > cheers I have tested it on P2020 board with 3 PCIe devices, each on own bus where each bus is connected to different PCIe controller / domain and it works correctly. Every PCIe device is on bus 1 bus but on different domains.
