Re: [RFC 1/2] arm64: PCI: Allow use arch-specific pci sysdata
From: Arnd Bergmann <arnd@kernel.org>
Date: 2021-03-20 12:53:13
Also in:
linux-arm-kernel, linux-pci, lkml
On Fri, Mar 19, 2021 at 5:22 PM Boqun Feng [off-list ref] wrote:
Currently, if an architecture selects CONFIG_PCI_DOMAINS_GENERIC, the ->sysdata in bus and bridge will be treated as struct pci_config_window, which is created by generic ECAM using the data from acpi. However, for a virtualized PCI bus, there might be no enough data in of or acpi table to create a pci_config_window. This is similar to the case where CONFIG_PCI_DOMAINS_GENERIC=n, IOW, architectures use their own structure for sysdata, so no apci table lookup is required. In order to enable Hyper-V's virtual PCI (which doesn't have acpi table entry for PCI) on ARM64 (which selects CONFIG_PCI_DOMAINS_GENERIC), we introduce arch-specific pci sysdata (similar to the one for x86) for ARM64, and allow the core PCI code to detect the type of sysdata at the runtime. The latter is achieved by adding a pci_ops::use_arch_sysdata field. Originally-by: Sunil Muthuswamy [off-list ref] Signed-off-by: Boqun Feng (Microsoft) <redacted>
I think this takes it in the opposite direction of where it should be going.
quoted hunk ↗ jump to hunk
--- arch/arm64/include/asm/pci.h | 29 +++++++++++++++++++++++++++++ arch/arm64/kernel/pci.c | 15 ++++++++++++--- include/linux/pci.h | 3 +++ 3 files changed, 44 insertions(+), 3 deletions(-)diff --git a/arch/arm64/include/asm/pci.h b/arch/arm64/include/asm/pci.h index b33ca260e3c9..dade061a0658 100644 --- a/arch/arm64/include/asm/pci.h +++ b/arch/arm64/include/asm/pci.h@@ -22,6 +22,16 @@ extern int isa_dma_bridge_buggy; +struct pci_sysdata { + int domain; /* PCI domain */ + int node; /* NUMA Node */ +#ifdef CONFIG_ACPI + struct acpi_device *companion; /* ACPI companion device */ +#endif +#ifdef CONFIG_PCI_MSI_IRQ_DOMAIN + void *fwnode; /* IRQ domain for MSI assignment */ +#endif +};
I think none of these members belong into sysdata or architecture specific code. The fact that a pci_host_bridge belongs to a particular NUMA node or i associated with a firmware description is neither specific to a host bridge implementation nor a CPU instruction set! Moreover, you cannot assume that all PCI host bridges on any given architecture can share the pci_sysdata pointer, it is purely specific to the bridge driver. A good start would be to move the members (one at a time) into struct pci_host_bridge and out of the sysdata of individual host bridge drivers.
quoted hunk ↗ jump to hunk
diff --git a/arch/arm64/kernel/pci.c b/arch/arm64/kernel/pci.c index 1006ed2d7c60..63d420d57e63 100644 --- a/arch/arm64/kernel/pci.c +++ b/arch/arm64/kernel/pci.c@@ -74,15 +74,24 @@ struct acpi_pci_generic_root_info { int acpi_pci_bus_find_domain_nr(struct pci_bus *bus) { struct pci_config_window *cfg = bus->sysdata; - struct acpi_device *adev = to_acpi_device(cfg->parent); - struct acpi_pci_root *root = acpi_driver_data(adev); + struct pci_sysdata *sd = bus->sysdata; + struct acpi_device *adev; + struct acpi_pci_root *root;
There should be no reason to add even most code to this file,
it should in fact become empty as it gets generalized more.
Arnd