Index: head/sys/dev/pci/pci_host_generic.h
===================================================================
--- head/sys/dev/pci/pci_host_generic.h
+++ head/sys/dev/pci/pci_host_generic.h
@@ -56,6 +56,8 @@
 	struct rman		io_rman;
 	struct resource		*res;
 	struct resource		*res1;
+	int			bus_start;
+	int			bus_end;
 	int			ecam;
 	bus_space_tag_t		bst;
 	bus_space_handle_t	bsh;
Index: head/sys/dev/pci/pci_host_generic.c
===================================================================
--- head/sys/dev/pci/pci_host_generic.c
+++ head/sys/dev/pci/pci_host_generic.c
@@ -147,13 +147,14 @@
 	uint64_t offset;
 	uint32_t data;
 
-	if ((bus > PCI_BUSMAX) || (slot > PCI_SLOTMAX) ||
-	    (func > PCI_FUNCMAX) || (reg > PCIE_REGMAX))
+	sc = device_get_softc(dev);
+	if ((bus < sc->bus_start) || (bus > sc->bus_end))
 		return (~0U);
+	if ((slot > PCI_SLOTMAX) || (func > PCI_FUNCMAX) ||
+	    (reg > PCIE_REGMAX))
+		return (~0U);
 
-	sc = device_get_softc(dev);
-
-	offset = PCIE_ADDR_OFFSET(bus, slot, func, reg);
+	offset = PCIE_ADDR_OFFSET(bus - sc->bus_start, slot, func, reg);
 	t = sc->bst;
 	h = sc->bsh;
 
@@ -183,14 +184,15 @@
 	bus_space_tag_t t;
 	uint64_t offset;
 
-	if ((bus > PCI_BUSMAX) || (slot > PCI_SLOTMAX) ||
-	    (func > PCI_FUNCMAX) || (reg > PCIE_REGMAX))
+	sc = device_get_softc(dev);
+	if ((bus < sc->bus_start) || (bus > sc->bus_end))
 		return;
+	if ((slot > PCI_SLOTMAX) || (func > PCI_FUNCMAX) ||
+	    (reg > PCIE_REGMAX))
+		return;
 
-	sc = device_get_softc(dev);
+	offset = PCIE_ADDR_OFFSET(bus - sc->bus_start, slot, func, reg);
 
-	offset = PCIE_ADDR_OFFSET(bus, slot, func, reg);
-
 	t = sc->bst;
 	h = sc->bsh;
 
@@ -221,14 +223,11 @@
     uintptr_t *result)
 {
 	struct generic_pcie_core_softc *sc;
-	int secondary_bus;
 
 	sc = device_get_softc(dev);
 
 	if (index == PCIB_IVAR_BUS) {
-		/* this pcib adds only pci bus 0 as child */
-		secondary_bus = 0;
-		*result = secondary_bus;
+		*result = sc->bus_start;
 		return (0);
 
 	}
Index: head/sys/dev/pci/pci_host_generic_acpi.c
===================================================================
--- head/sys/dev/pci/pci_host_generic_acpi.c
+++ head/sys/dev/pci/pci_host_generic_acpi.c
@@ -125,7 +125,7 @@
 	struct generic_pcie_acpi_softc *sc;
 	ACPI_HANDLE handle;
 	ACPI_STATUS status;
-	int error;
+	int error, bus_start;
 
 	sc = device_get_softc(dev);
 
@@ -136,10 +136,14 @@
 		device_printf(dev, "Bus is%s cache-coherent\n",
 		    sc->base.coherent ? "" : " not");
 
-	if (!ACPI_FAILURE(acpi_GetInteger(handle, "_BBN", &sc->base.ecam)))
-		sc->base.ecam >>= 7;
-	else
+	if (!ACPI_FAILURE(acpi_GetInteger(handle, "_BBN", &bus_start))) {
+		sc->base.ecam = bus_start >> 7;
+		sc->base.bus_start = bus_start & 0x7F;
+	} else {
 		sc->base.ecam = 0;
+		sc->base.bus_start = 0;
+	}
+	sc->base.bus_end = 0xFF;
 
 	acpi_pcib_fetch_prt(dev, &sc->ap_prt);
 
@@ -194,17 +198,12 @@
 generic_pcie_acpi_read_ivar(device_t dev, device_t child, int index,
     uintptr_t *result)
 {
-	ACPI_HANDLE handle;
 	struct generic_pcie_acpi_softc *sc;
-	int secondary_bus;
 
 	sc = device_get_softc(dev);
 
 	if (index == PCIB_IVAR_BUS) {
-		handle = acpi_get_handle(dev);
-		if (ACPI_FAILURE(acpi_GetInteger(handle, "_BBN", &secondary_bus)))
-			secondary_bus = sc->base.ecam * 0x80;
-		*result = secondary_bus;
+		*result = sc->base.ecam * 0x80 + sc->base.bus_start;
 		return (0);
 	}
 
Index: head/sys/dev/pci/pci_host_generic_fdt.c
===================================================================
--- head/sys/dev/pci/pci_host_generic_fdt.c
+++ head/sys/dev/pci/pci_host_generic_fdt.c
@@ -152,6 +152,9 @@
 		device_printf(dev, "Bus is%s cache-coherent\n",
 		    sc->base.coherent ? "" : " not");
 
+	/* TODO parse FDT bus ranges */
+	sc->base.bus_start = 0;
+	sc->base.bus_end = 0xFF;
 	error = pci_host_generic_core_attach(dev);
 	if (error != 0)
 		return (error);