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?
> config PPC_OF_PLATFORM_PCI
> bool
> depends on PCI
> diff --git a/arch/powerpc/kernel/pci_32.c b/arch/powerpc/kernel/pci_32.c
> index 2f7284b68f06..433965bf37b4 100644
> --- a/arch/powerpc/kernel/pci_32.c
> +++ b/arch/powerpc/kernel/pci_32.c
> @@ -239,7 +239,9 @@ void pcibios_setup_phb_io_space(struct pci_controller *hose)
> static int __init pcibios_init(void)
> {
> struct pci_controller *hose, *tmp;
> +#ifndef CONFIG_PPC_PCI_BUS_NUM_DOMAIN_DEPENDENT
> int next_busno = 0;
> +#endif
>
> printk(KERN_INFO "PCI: Probing PCI hardware\n");
>
> @@ -248,13 +250,17 @@ static int __init pcibios_init(void)
>
> /* Scan all of the recorded PCI controllers. */
> list_for_each_entry_safe(hose, tmp, &hose_list, list_node) {
> +#ifndef CONFIG_PPC_PCI_BUS_NUM_DOMAIN_DEPENDENT
> if (pci_assign_all_buses)
> hose->first_busno = next_busno;
> +#endif
> hose->last_busno = 0xff;
> pcibios_scan_phb(hose);
> pci_bus_add_devices(hose->bus);
> +#ifndef CONFIG_PPC_PCI_BUS_NUM_DOMAIN_DEPENDENT
> if (pci_assign_all_buses || next_busno <= hose->last_busno)
> next_busno = hose->last_busno + pcibios_assign_bus_offset;
> +#endif
> }
>
> #if defined(CONFIG_PPC_PMAC) || defined(CONFIG_PPC_CHRP)
> --
> 2.20.1
>
