[PATCH V8 9/9] pci, acpi: ARM64 support for ACPI based generic PCI host controller

[Tomasz Nowicki]

This patch implements pci_acpi_scan_root call so that ARM64 can start
using ACPI to setup and enumerate PCI buses.

The implementation of pci_acpi_scan_root() looks up config space regions
through MCFG interface. Then ECAM library is doing a new mapping
and attach generic ECAM ops which are used for accessing config space.

On ARM64, ACPI and DT can be enabled together, and in that case
we need to use generic domains. In order to do that we implement
ARM64 specific way of retrieving domain number from pci_config_window
structure.

Since we enable PCI for ACPI we need to implement raw_pci_{read|write}
at the same time. ARM64 provides RAW accessors as long as there is
correlated valid pci_bus structure, but not before.

Signed-off-by: Tomasz Nowicki <tn@xxxxxxxxxxxx>
Signed-off-by: Jayachandran C <jchandra@xxxxxxxxxxxx>
---
 arch/arm64/Kconfig      |   2 +
 arch/arm64/kernel/pci.c | 120 ++++++++++++++++++++++++++++++++++++++++++++++--
 include/linux/pci.h     |   5 ++
 3 files changed, 122 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 76747d9..87c48ad 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -3,6 +3,7 @@ config ARM64
 	select ACPI_CCA_REQUIRED if ACPI
 	select ACPI_GENERIC_GSI if ACPI
 	select ACPI_REDUCED_HARDWARE_ONLY if ACPI
+	select ACPI_MCFG if ACPI
 	select ARCH_HAS_DEVMEM_IS_ALLOWED
 	select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
 	select ARCH_HAS_ELF_RANDOMIZE
@@ -96,6 +97,7 @@ config ARM64
 	select OF_EARLY_FLATTREE
 	select OF_NUMA if NUMA && OF
 	select OF_RESERVED_MEM
+	select PCI_ECAM if ACPI
 	select PERF_USE_VMALLOC
 	select POWER_RESET
 	select POWER_SUPPLY
diff --git a/arch/arm64/kernel/pci.c b/arch/arm64/kernel/pci.c
index 3663be1..39f2a40 100644
--- a/arch/arm64/kernel/pci.c
+++ b/arch/arm64/kernel/pci.c
@@ -17,7 +17,9 @@
 #include <linux/mm.h>
 #include <linux/of_pci.h>
 #include <linux/of_platform.h>
+#include <linux/pci.h>
 #include <linux/pci-acpi.h>
+#include <linux/pci-ecam.h>
 #include <linux/slab.h>
 
 /*
@@ -71,13 +73,21 @@ int pcibios_alloc_irq(struct pci_dev *dev)
 int raw_pci_read(unsigned int domain, unsigned int bus,
 		  unsigned int devfn, int reg, int len, u32 *val)
 {
-	return -ENXIO;
+	struct pci_bus *b = pci_find_bus(domain, bus);
+
+	if (!b)
+		return PCIBIOS_DEVICE_NOT_FOUND;
+	return b->ops->read(b, devfn, reg, len, val);
 }
 
 int raw_pci_write(unsigned int domain, unsigned int bus,
 		unsigned int devfn, int reg, int len, u32 val)
 {
-	return -ENXIO;
+	struct pci_bus *b = pci_find_bus(domain, bus);
+
+	if (!b)
+		return PCIBIOS_DEVICE_NOT_FOUND;
+	return b->ops->write(b, devfn, reg, len, val);
 }
 
 #ifdef CONFIG_NUMA
@@ -91,11 +101,111 @@ EXPORT_SYMBOL(pcibus_to_node);
 #endif
 
 #ifdef CONFIG_ACPI
-/* Root bridge scanning */
+
+struct acpi_pci_generic_root_info {
+	struct acpi_pci_root_info	common;
+	struct pci_config_window	*cfg;	/* config space mapping */
+};
+
+int acpi_pci_bus_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);
+
+	return root->segment;
+}
+
+int pcibios_root_bridge_prepare(struct pci_host_bridge *bridge)
+{
+	if (!acpi_disabled) {
+		struct pci_config_window *cfg = bridge->bus->sysdata;
+		struct acpi_device *adev = to_acpi_device(cfg->parent);
+		ACPI_COMPANION_SET(&bridge->dev, adev);
+	}
+
+	return 0;
+}
+
+/*
+ * Lookup the bus range for the domain in MCFG, and set up config space
+ * mapping.
+ */
+static int pci_acpi_setup_ecam_mapping(struct acpi_pci_root *root,
+				       struct acpi_pci_generic_root_info *ri)
+{
+	struct resource *bus_res = &root->secondary;
+	u16 seg = root->segment;
+	struct pci_config_window *cfg;
+	struct resource cfgres;
+	unsigned int bsz;
+	int err;
+
+	err = pci_mcfg_lookup(root);
+	if (err) {
+		pr_err("%04x:%pR MCFG region not found\n", seg, bus_res);
+		return err;
+	}
+
+	bsz = 1 << pci_generic_ecam_ops.bus_shift;
+	cfgres.start = root->mcfg_addr + bus_res->start * bsz;
+	cfgres.end = cfgres.start + resource_size(bus_res) * bsz - 1;
+	cfgres.flags = IORESOURCE_MEM;
+	cfg = pci_ecam_create(&root->device->dev, &cfgres, bus_res,
+			      &pci_generic_ecam_ops);
+	if (IS_ERR(cfg)) {
+		pr_err("%04x:%pR error %ld mapping CAM\n", seg, bus_res,
+		       PTR_ERR(cfg));
+		return PTR_ERR(cfg);
+	}
+
+	ri->cfg = cfg;
+	return 0;
+}
+
+/* release_info: free resrouces allocated by init_info */
+static void pci_acpi_generic_release_info(struct acpi_pci_root_info *ci)
+{
+	struct acpi_pci_generic_root_info *ri;
+
+	ri = container_of(ci, struct acpi_pci_generic_root_info, common);
+	pci_ecam_free(ri->cfg);
+	kfree(ri);
+}
+
+static struct acpi_pci_root_ops acpi_pci_root_ops = {
+	.release_info = pci_acpi_generic_release_info,
+};
+
+/* Interface called from ACPI code to setup PCI host controller */
 struct pci_bus *pci_acpi_scan_root(struct acpi_pci_root *root)
 {
-	/* TODO: Should be revisited when implementing PCI on ACPI */
-	return NULL;
+	int node = acpi_get_node(root->device->handle);
+	struct acpi_pci_generic_root_info *ri;
+	struct pci_bus *bus, *child;
+	int err;
+
+	ri = kzalloc_node(sizeof(*ri), GFP_KERNEL, node);
+	if (!ri)
+		return NULL;
+
+	err = pci_acpi_setup_ecam_mapping(root, ri);
+	if (err)
+		return NULL;
+
+	acpi_pci_root_ops.pci_ops = &ri->cfg->ops->pci_ops;
+	bus = acpi_pci_root_create(root, &acpi_pci_root_ops, &ri->common,
+				   ri->cfg);
+	if (!bus)
+		return NULL;
+
+	pci_bus_size_bridges(bus);
+	pci_bus_assign_resources(bus);
+
+	list_for_each_entry(child, &bus->children, node)
+		pcie_bus_configure_settings(child);
+
+	return bus;
 }
 
 void pcibios_add_bus(struct pci_bus *bus)
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 9661c85..f66d188 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1390,7 +1390,12 @@ static inline int pci_domain_nr(struct pci_bus *bus)
 {
 	return bus->domain_nr;
 }
+/* Arch specific ACPI hook to set-up domain number */
+#ifdef CONFIG_ACPI
+int acpi_pci_bus_domain_nr(struct pci_bus *bus);
+#else
 static inline int acpi_pci_bus_domain_nr(struct pci_bus *bus) { return -1; }
+#endif
 void pci_bus_assign_domain_nr(struct pci_bus *bus, struct device *parent);
 #else
 static inline void pci_bus_assign_domain_nr(struct pci_bus *bus,
-- 
1.9.1