Messages in this thread | | | Date | Wed, 6 Jul 2022 12:23:43 +0200 | From | Pali Rohár <> | Subject | Re: [PATCH] powerpc/pci: Add config option for using OF 'reg' for PCI domain |
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On Friday 10 June 2022 17:33:32 Michael Ellerman wrote: > Pali Rohár <pali@kernel.org> writes: > > Since commit 63a72284b159 ("powerpc/pci: Assign fixed PHB number based on > > device-tree properties"), powerpc kernel always fallback to PCI domain > > assignment from OF / Device Tree 'reg' property of the PCI controller. > > > > PCI code for other Linux architectures use increasing assignment of the PCI > > domain for individual controllers (assign the first free number), like it > > was also for powerpc prior mentioned commit. > > > > Upgrading powerpc kernels from LTS 4.4 version (which does not contain > > mentioned commit) to new LTS versions brings a regression in domain > > assignment. > > I'm sorry this broke your system. But I don't really consider it a > regression, the kernel provides no guarantee about the PCI domain > numbering across LTS releases. > > Prior to the change the numbering was just based on the order the PHBs > were discovered in the device tree, which is not robust. A cosmetic > refactor of the device tree source could cause PHBs to be discovered in > a different order. > > Similarly a change in firmware PCI discovery or device tree generation > could cause the numbering to change. > > If you have scripts that are looking for certain devices they can use > the vendor/device fields in sysfs to find the actual devices they want, > not just whatever happens to be at 0000:01:00.0. > > > Fix this issue by introducing a new option CONFIG_PPC_PCI_DOMAIN_FROM_OF_REG > > When this options is disabled then powerpc kernel would assign PCI domains > > in the similar way like it is doing kernel for other architectures and also > > how it was done prior that commit. > > I really don't want a config option for that. > > There is a device tree property "linux,pci-domain", described in > Documentation/devicetree/bindings/pci/pci.txt. > > Can you try adding that to your device tree and updating > get_phb_number() to look for it? > > cheers
I sent another proposal in V2, now also with "linux,pci-domain" support.
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