[RFC 1/2] arm64: PCI: Allow use arch-specific pci sysdata

[Boqun Feng]

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 <sunilmut@xxxxxxxxxxxxx>
Signed-off-by: Boqun Feng (Microsoft) <boqun.feng@xxxxxxxxx>
---
 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
+};
 #ifdef CONFIG_PCI
 static inline int pci_get_legacy_ide_irq(struct pci_dev *dev, int channel)
 {
@@ -31,8 +41,27 @@ static inline int pci_get_legacy_ide_irq(struct pci_dev *dev, int channel)
 
 static inline int pci_proc_domain(struct pci_bus *bus)
 {
+	if (bus->ops->use_arch_sysdata)
+		return pci_domain_nr(bus);
 	return 1;
 }
+#ifdef CONFIG_PCI_MSI_IRQ_DOMAIN
+static inline void *_pci_root_bus_fwnode(struct pci_bus *bus)
+{
+	struct pci_sysdata *sd = bus->sysdata;
+
+	if (bus->ops->use_arch_sysdata)
+		return sd->fwnode;
+
+	/*
+	 * bus->sysdata is not struct pci_sysdata, fwnode should be able to
+	 * be queried from of/acpi.
+	 */
+	return NULL;
+}
+#define pci_root_bus_fwnode	_pci_root_bus_fwnode
+#endif /* CONFIG_PCI_MSI_IRQ_DOMAIN */
+
 #endif  /* CONFIG_PCI */
 
 #endif  /* __ASM_PCI_H */
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;
+
+	/* struct pci_sysdata has domain nr in it */
+	if (bus->ops->use_arch_sysdata)
+		return sd->domain;
+
+	/* or pci_config_window is used as sysdata */
+	adev = to_acpi_device(cfg->parent);
+	root = acpi_driver_data(adev);
 
 	return root->segment;
 }
 
 int pcibios_root_bridge_prepare(struct pci_host_bridge *bridge)
 {
-	if (!acpi_disabled) {
+	if (!acpi_disabled && bridge->ops->use_arch_sysdata) {
 		struct pci_config_window *cfg = bridge->bus->sysdata;
 		struct acpi_device *adev = to_acpi_device(cfg->parent);
 		struct device *bus_dev = &bridge->bus->dev;
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 86c799c97b77..4036aac40361 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -740,6 +740,9 @@ struct pci_ops {
 	void __iomem *(*map_bus)(struct pci_bus *bus, unsigned int devfn, int where);
 	int (*read)(struct pci_bus *bus, unsigned int devfn, int where, int size, u32 *val);
 	int (*write)(struct pci_bus *bus, unsigned int devfn, int where, int size, u32 val);
+#ifdef CONFIG_PCI_DOMAINS_GENERIC
+	int use_arch_sysdata;	/* ->sysdata is arch-specific */
+#endif
 };
 
 /*
-- 
2.30.2