[PATCH 6.6 133/283] PCI: Log bridge info when first enumerating bridge

Sasha Levin
2026-02-28T18:09:00Z

From: Bjorn Helgaas <bhelgaas@google.com>

[ Upstream commit 95140c2fbfdf3b6ca98578e5bdbc82d9922f08b9 ]

Log bridge secondary/subordinate bus and window information at the same
time we log the bridge BARs, just after discovering the bridge and before
scanning the bridge's secondary bus. This logs the bridge and downstream
devices in a more logical order:

- pci 0000:00:01.0: [8086:1901] type 01 class 0x060400
- pci 0000:01:00.0: [10de:13b6] type 00 class 0x030200
- pci 0000:01:00.0: reg 0x10: [mem 0xec000000-0xecffffff]
- pci 0000:00:01.0: PCI bridge to [bus 01]
- pci 0000:00:01.0: bridge window [io 0xe000-0xefff]

+ pci 0000:00:01.0: [8086:1901] type 01 class 0x060400
+ pci 0000:00:01.0: PCI bridge to [bus 01]
+ pci 0000:00:01.0: bridge window [io 0xe000-0xefff]
+ pci 0000:01:00.0: [10de:13b6] type 00 class 0x030200
+ pci 0000:01:00.0: reg 0x10: [mem 0xec000000-0xecffffff]

Note that we read the windows into a temporary struct resource that is
thrown away, not into the resources in the struct pci_bus.

The windows may be adjusted after we know what downstream devices require,
and those adjustments are logged as they are made.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Stable-dep-of: 9abf79c8d7b4 ("PCI/ACPI: Restrict program_hpx_type2() to AER bits")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/pci/probe.c | 23 +++++++++++++++++++----
1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index f7b01cddf5abf..8a2f1e57bee19 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -458,8 +458,17 @@ static void pci_read_bridge_mmio_pref(struct pci_dev *dev, struct resource *res,

static void pci_read_bridge_windows(struct pci_dev *bridge)
{
+ u32 buses;
u16 io;
u32 pmem, tmp;
+ struct resource res;
+
+ pci_read_config_dword(bridge, PCI_PRIMARY_BUS, &buses);
+ res.flags = IORESOURCE_BUS;
+ res.start = (buses >> 8) & 0xff;
+ res.end = (buses >> 16) & 0xff;
+ pci_info(bridge, "PCI bridge to %pR%s\n", &res,
+ bridge->transparent ? " (subtractive decode)" : "");

pci_read_config_word(bridge, PCI_IO_BASE, &io);
if (!io) {
@@ -467,8 +476,12 @@ static void pci_read_bridge_windows(struct pci_dev *bridge)
pci_read_config_word(bridge, PCI_IO_BASE, &io);
pci_write_config_word(bridge, PCI_IO_BASE, 0x0);
}
- if (io)
+ if (io) {
bridge->io_window = 1;
+ pci_read_bridge_io(bridge, &res, true);
+ }
+
+ pci_read_bridge_mmio(bridge, &res, true);

/*
* DECchip 21050 pass 2 errata: the bridge may miss an address
@@ -505,6 +518,8 @@ static void pci_read_bridge_windows(struct pci_dev *bridge)
if (tmp)
bridge->pref_64_window = 1;
}
+
+ pci_read_bridge_mmio_pref(bridge, &res, true);
}

void pci_read_bridge_bases(struct pci_bus *child)
@@ -524,9 +539,9 @@ void pci_read_bridge_bases(struct pci_bus *child)
for (i = 0; i < PCI_BRIDGE_RESOURCE_NUM; i++)
child->resource[i] = &dev->resource[PCI_BRIDGE_RESOURCES+i];

- pci_read_bridge_io(child->self, child->resource[0], true);
- pci_read_bridge_mmio(child->self, child->resource[1], true);
- pci_read_bridge_mmio_pref(child->self, child->resource[2], true);
+ pci_read_bridge_io(child->self, child->resource[0], false);
+ pci_read_bridge_mmio(child->self, child->resource[1], false);
+ pci_read_bridge_mmio_pref(child->self, child->resource[2], false);

if (dev->transparent) {
pci_bus_for_each_resource(child->parent, res) {
--
2.51.0