Le 04/05/2022 à 19:57, Pali Rohár a écrit :
> 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.
Can you elaborate why it is a regression ?
That commit says 'no functionnal changes', I'm having hard time
understanding how a nochange can be a regression.
Usually we don't commit regressions to mainline ...
>
> 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.
You don't define CONFIG_PPC_PCI_DOMAIN_FROM_OF_REG on by default, it
means this commit will change the behaviour. Is that expected ?
Is that really worth a user selectable option ? Is the user able to
decide what he needs ?
>
> Fixes: 63a72284b159 ("powerpc/pci: Assign fixed PHB number based on
> device-tree properties")
Is that really a fix ? What is the problem really ?
> Signed-off-by: Pali Rohár <p...@kernel.org>
> ---
> arch/powerpc/Kconfig | 10 ++++++++++
> arch/powerpc/kernel/pci-common.c | 4 ++--
> 2 files changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 174edabb74fa..4dd3e3acddda 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -375,6 +375,16 @@ config PPC_OF_PLATFORM_PCI
> depends on PCI
> depends on PPC64 # not supported on 32 bits yet
>
> +config PPC_PCI_DOMAIN_FROM_OF_REG
> + bool "Use OF reg property for PCI domain"
> + depends on PCI
Should it depend on PPC_OF_PLATFORM_PCI instead ?
> + help
> + By default PCI domain for host bridge during its registration is
> + chosen as the lowest unused PCI domain number.
> +
> + When this option is enabled then PCI domain is determined from
> + the OF / Device Tree 'reg' property.
> +
> config ARCH_SUPPORTS_UPROBES
> def_bool y
>
> diff --git a/arch/powerpc/kernel/pci-common.c
> b/arch/powerpc/kernel/pci-common.c
> index 8bc9cf62cd93..8cb6fc5302ae 100644
> --- a/arch/powerpc/kernel/pci-common.c
> +++ b/arch/powerpc/kernel/pci-common.c
> @@ -74,7 +74,6 @@ void __init set_pci_dma_ops(const struct dma_map_ops
> *dma_ops)
> static int get_phb_number(struct device_node *dn)
> {
> int ret, phb_id = -1;
> - u32 prop_32;
> u64 prop;
>
> /*
> @@ -83,7 +82,8 @@ static int get_phb_number(struct device_node *dn)
> * reading "ibm,opal-phbid", only present in OPAL environment.
> */
> ret = of_property_read_u64(dn, "ibm,opal-phbid", &prop);
This looks like very specific, it is not reflected in the commit log.
> - if (ret) {
> + if (ret && IS_ENABLED(CONFIG_PPC_PCI_DOMAIN_FROM_OF_REG)) {
> + u32 prop_32;
> ret = of_property_read_u32_index(dn, "reg", 1, &prop_32);
> prop = prop_32;
> }
