[PATCH] PCI: quirks: Skip nv_msi_ht_cap_quirk when host bridge 00:00.0 is absent

[Karl Mehltretter <kmehltretter@gmail.com>]

__nv_msi_ht_cap_quirk() runs on all PCI_VENDOR_ID_NVIDIA devices to
enable or disable HyperTransport MSI mapping relative to a host bridge
at bus 0, slot 0, function 0.

On NVIDIA Tegra SoCs (such as Tegra210 on Jetson Nano), the PCIe
controller exposes root ports at 00:01.0 and 00:02.0 with no device at
00:00.0, and the root port's HT MSI mapping capability is already
disabled (found == 1). Looking up 00:00.0 returns NULL and logs a
false-positive warning on every boot:

  pci 0000:00:02.0: nv_msi_ht_cap_quirk didn't locate host bridge

Return silently when no 00:00.0 device exists on the domain, matching
nv_ht_enable_msi_mapping().

Assisted-by: LLM
Signed-off-by: Karl Mehltretter <kmehltretter@gmail.com>
---
Observed on a Jetson Nano 4GB (Tegra210, p3450-0000) booting v7.3
(c03c1a14507d), where the Tegra PCIe controller (1003000.pcie)
enumerates the active root port at 0000:00:02.0 ([10de:0faf]) with no
0000:00:00.0 device on bus 00:

  pci 0000:00:02.0: [10de:0faf] type 01 class 0x060400 PCIe Root Port
  pci 0000:00:02.0: nv_msi_ht_cap_quirk didn't locate host bridge

 drivers/pci/quirks.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index 1aa87a3..47778c1 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -3115,10 +3115,8 @@ static void __nv_msi_ht_cap_quirk(struct pci_dev *dev, int all)
 	 */
 	host_bridge = pci_get_domain_bus_and_slot(pci_domain_nr(dev->bus), 0,
 						  PCI_DEVFN(0, 0));
-	if (host_bridge == NULL) {
-		pci_warn(dev, "nv_msi_ht_cap_quirk didn't locate host bridge\n");
+	if (!host_bridge)
 		return;
-	}
 
 	pos = pci_find_ht_capability(host_bridge, HT_CAPTYPE_SLAVE);
 	if (pos != 0) {

base-commit: c03c1a14507dfaf8b856c2608f9ac216021fc222
-- 
2.39.5 (Apple Git-154)