[PATCH v5 1/3] PCI: Cache bridge firmware secondary bus number

[Mario Limonciello <mario.limonciello@amd.com>]

Bridge scans are split into two passes when bus numbers need reassigning.
Save the firmware secondary bus number on the bridge pci_dev during pass 0,
before the bridge is disabled, and keep it for pass 1 so devices discovered
there can read the original bus number via their upstream bridge.

Guard the cached value with a validity flag so later rescans do not overwrite
it with the renumbered runtime value.

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
 drivers/pci/probe.c | 4 ++++
 include/linux/pci.h | 3 +++
 2 files changed, 7 insertions(+)

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 27008e2ea5afc..14b3dd7dac271 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1418,6 +1418,10 @@ static int pci_scan_bridge_extend(struct pci_bus *bus, struct pci_dev *dev,
 
 	pci_dbg(dev, "scanning [bus %02x-%02x] behind bridge, pass %d\n",
 		secondary, subordinate, pass);
+	if (!pass && !dev->fw_sec_busnr_valid) {
+		dev->fw_sec_busnr = secondary;
+		dev->fw_sec_busnr_valid = true;
+	}
 
 	if (!primary && (primary != bus->number) && secondary && subordinate) {
 		pci_warn(dev, "Primary bus is hard wired to 0\n");
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 5ffcf5ce8c966..b942dbb4edf57 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 */
+	/* Firmware secondary bus number saved across bridge scan passes */
+	unsigned char	fw_sec_busnr;
 	unsigned short	vendor;
 	unsigned short	device;
 	unsigned short	subsystem_vendor;
@@ -414,6 +416,7 @@ struct pci_dev {
 	unsigned int	pme_poll:1;	/* Poll device's PME status bit */
 	unsigned int	pinned:1;	/* Whether this dev is pinned */
 	unsigned int	config_rrs_sv:1; /* Config RRS software visibility */
+	unsigned int	fw_sec_busnr_valid:1;
 	unsigned int	imm_ready:1;	/* Supports Immediate Readiness */
 	unsigned int	d1_support:1;	/* Low power state D1 is supported */
 	unsigned int	d2_support:1;	/* Low power state D2 is supported */

-- 
2.43.0