diff --git a/drivers/pci/host/pcie-mediatek.c b/drivers/pci/host/pcie-mediatek.c
index db93efdf1d63..c896bb9ef968 100644
--- a/drivers/pci/host/pcie-mediatek.c
+++ b/drivers/pci/host/pcie-mediatek.c
@@ -333,6 +333,17 @@ static struct mtk_pcie_port *mtk_pcie_find_port(struct pci_bus *bus,
 {
 	struct mtk_pcie *pcie = bus->sysdata;
 	struct mtk_pcie_port *port;
+	struct pci_dev *dev = NULL;
+
+	/*
+	 * Walk the bus hierarchy to get the devfn value
+	 * of the port in the root bus.
+	 */
+	while (bus && bus->number) {
+		dev = bus->self;
+		bus = dev->bus;
+		devfn = dev->devfn;
+	}
 
 	list_for_each_entry(port, &pcie->ports, list)
 		if (port->slot == PCI_SLOT(devfn))