[PATCH V1 10/11] pci, acpi: Provide generic way to assign bus domain number.

[Tomasz Nowicki <tn@semihalf.com>]

Architectures which support PCI_DOMAINS_GENERIC (like ARM64)
cannot call pci_bus_assign_domain_nr along ACPI PCI host bridge
initialization since this function needs valid parent device reference
to be able to retrieve domain number (aka segment).

We can omit that blocker and pass down host bridge device via
pci_create_root_bus parameter and then be able to evaluate _SEG method
being in pci_bus_assign_domain_nr.

Note that _SEG method is optional, therefore _SEG absence means
that all PCI buses belong to domain 0.

Signed-off-by: Tomasz Nowicki <tn@semihalf.com>
---
 drivers/acpi/pci_root.c |  2 +-
 drivers/pci/pci.c       | 32 +++++++++++++++++++++++++++-----
 2 files changed, 28 insertions(+), 6 deletions(-)

diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index 850d7bf..e682dc6 100644
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -839,7 +839,7 @@ struct pci_bus *acpi_pci_root_create(struct acpi_pci_root *root,
 
 	pci_acpi_root_add_resources(info);
 	pci_add_resource(&info->resources, &root->secondary);
-	bus = pci_create_root_bus(NULL, busnum, ops->pci_ops,
+	bus = pci_create_root_bus(&device->dev, busnum, ops->pci_ops,
 				  sysdata, &info->resources);
 	if (!bus)
 		goto out_release_info;
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 6a9a111..17d1857 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -25,6 +25,7 @@
 #include <linux/device.h>
 #include <linux/pm_runtime.h>
 #include <linux/pci_hotplug.h>
+#include <linux/acpi.h>
 #include <asm-generic/pci-bridge.h>
 #include <asm/setup.h>
 #include "pci.h"
@@ -4501,7 +4502,7 @@ int pci_get_new_domain_nr(void)
 void pci_bus_assign_domain_nr(struct pci_bus *bus, struct device *parent)
 {
 	static int use_dt_domains = -1;
-	int domain = of_get_pci_domain_nr(parent->of_node);
+	int domain;
 
 	/*
 	 * Check DT domain and use_dt_domains values.
@@ -4523,14 +4524,35 @@ void pci_bus_assign_domain_nr(struct pci_bus *bus, struct device *parent)
 	 * API and update the use_dt_domains value to keep track of method we
 	 * are using to assign domain numbers (use_dt_domains = 0).
 	 *
+	 * IF ACPI, we expect non-DT method (use_dt_domains == -1)
+	 * and call _SEG method for corresponding host bridge device.
+	 * If _SEG method does not exist, following ACPI spec (6.5.6)
+	 * all PCI buses belong to domain 0.
+	 *
 	 * All other combinations imply we have a platform that is trying
-	 * to mix domain numbers obtained from DT and pci_get_new_domain_nr(),
-	 * which is a recipe for domain mishandling and it is prevented by
-	 * invalidating the domain value (domain = -1) and printing a
-	 * corresponding error.
+	 * to mix domain numbers obtained from DT, ACPI and
+	 * pci_get_new_domain_nr(), which is a recipe for domain mishandling and
+	 * it is prevented by invalidating the domain value (domain = -1) and
+	 * printing a corresponding error.
 	 */
+
+	domain = of_get_pci_domain_nr(parent->of_node);
 	if (domain >= 0 && use_dt_domains) {
 		use_dt_domains = 1;
+#ifdef CONFIG_ACPI
+	} else if (!acpi_disabled && use_dt_domains == -1) {
+		struct acpi_device *acpi_dev = to_acpi_device(parent);
+		unsigned long long segment = 0;
+		acpi_status status;
+
+		status = acpi_evaluate_integer(acpi_dev->handle,
+					       METHOD_NAME__SEG, NULL,
+					       &segment);
+		if (ACPI_FAILURE(status) && status != AE_NOT_FOUND)
+			dev_err(&acpi_dev->dev,  "can't evaluate _SEG\n");
+
+		domain = segment;
+#endif
 	} else if (domain < 0 && use_dt_domains != 1) {
 		use_dt_domains = 0;
 		domain = pci_get_new_domain_nr();
-- 
1.9.1