[PATCH v2 1/3] PCI: Preserve the initial bus number in pci_dev

[Mario Limonciello]

Bridges that need bus reassignment are scanned in two passes. Save
the firmware secondary bus number during the first pass, before the
bridge is disabled, and carry it to the bus created in the second
pass. Initialize pci_dev from this preserved bus number so drivers
can match firmware records after PCI bus renumbering.

Handle pci_alloc_dev(NULL) as well; some in-tree callers use it to
allocate a standalone pci_dev.

Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
---
 drivers/pci/probe.c | 9 +++++++++
 include/linux/pci.h | 3 +++
 2 files changed, 12 insertions(+)

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 27008e2ea5afc..4ece4b70cdc15 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1012,6 +1012,7 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge)
 	bus->sysdata = bridge->sysdata;
 	bus->ops = bridge->ops;
 	bus->number = bus->busn_res.start = bridge->busnr;
+	bus->initial_bus_number = bus->number;
 #ifdef CONFIG_PCI_DOMAINS_GENERIC
 	if (bridge->domain_nr == PCI_DOMAIN_NR_NOT_SET)
 		bus->domain_nr = pci_bus_find_domain_nr(bus, parent);
@@ -1232,6 +1233,7 @@ static struct pci_bus *pci_alloc_child_bus(struct pci_bus *parent,
 
 	/* Set up the primary, secondary and subordinate bus numbers */
 	child->number = child->busn_res.start = busnr;
+	child->initial_bus_number = busnr;
 	child->primary = parent->busn_res.start;
 	child->busn_res.end = 0xff;
 
@@ -1470,6 +1472,7 @@ static int pci_scan_bridge_extend(struct pci_bus *bus, struct pci_dev *dev,
 			child = pci_add_new_bus(bus, dev, secondary);
 			if (!child)
 				goto out;
+			child->initial_bus_number = secondary;
 			child->primary = primary;
 			pci_bus_insert_busn_res(child, secondary, subordinate);
 			child->bridge_ctl = bctl;
@@ -1491,6 +1494,8 @@ static int pci_scan_bridge_extend(struct pci_bus *bus, struct pci_dev *dev,
 		 * do in the second pass.
 		 */
 		if (!pass) {
+			if (!dev->initial_secondary_bus_number)
+				dev->initial_secondary_bus_number = secondary;
 			if (pcibios_assign_all_busses() || broken)
 
 				/*
@@ -1526,6 +1531,9 @@ static int pci_scan_bridge_extend(struct pci_bus *bus, struct pci_dev *dev,
 			child = pci_add_new_bus(bus, dev, next_busnr);
 			if (!child)
 				goto out;
+			if (dev->initial_secondary_bus_number)
+				child->initial_bus_number =
+					dev->initial_secondary_bus_number;
 			pci_bus_insert_busn_res(child, next_busnr,
 						bus->busn_res.end);
 		}
@@ -2508,6 +2516,7 @@ struct pci_dev *pci_alloc_dev(struct pci_bus *bus)
 	INIT_LIST_HEAD(&dev->bus_list);
 	dev->dev.type = &pci_dev_type;
 	dev->bus = pci_bus_get(bus);
+	dev->initial_bus_number = bus ? bus->initial_bus_number : 0;
 	dev->driver_exclusive_resource = (struct resource) {
 		.name = "PCI Exclusive",
 		.start = 0,
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 5ffcf5ce8c966..f6b377dcf7a14 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -363,6 +363,8 @@ struct pci_dev {
 	struct pci_slot	*slot;		/* Physical slot this device is in */
 
 	unsigned int	devfn;		/* Encoded device & function index */
+	u8		initial_bus_number;	/* Bus number when device was discovered */
+	u8		initial_secondary_bus_number;	/* Bus number behind this bridge */
 	unsigned short	vendor;
 	unsigned short	device;
 	unsigned short	subsystem_vendor;
@@ -724,6 +726,7 @@ struct pci_bus {
 	struct proc_dir_entry *procdir;	/* Directory entry in /proc/bus/pci */
 
 	unsigned char	number;		/* Bus number */
+	unsigned char	initial_bus_number;	/* Bus number before reassignment */
 	unsigned char	primary;	/* Number of primary bridge */
 	unsigned char	max_bus_speed;	/* enum pci_bus_speed */
 	unsigned char	cur_bus_speed;	/* enum pci_bus_speed */

-- 
2.43.0