PCI: designware: Parse bus-range property from devicetree

This allows to explicitly specify the covered bus numbers in the
devicetree, which will come in handy once we see a SoC with more than one
PCIe host controller instance.

Previously the driver relied on the behavior of pci_scan_root_bus() to fill
in a range of 0x00-0xff if no valid range was found.  We fall back to the
same range if no valid DT entry was found to keep backwards compatibility,
but now do it explicitly.

[bhelgaas: use %pR in error message to avoid duplication]
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Pratyush Anand <pratyush.anand@st.com>
Acked-by: Mohit Kumar <mohit.kumar@st.com>

Documentation/devicetree/bindings/pci/designware-pcie.txt

@@ -23,3 +23,6 @@ Required properties:
 
 Optional properties:
 - reset-gpio: gpio pin number of power good signal
+- bus-range: PCI bus numbers covered (it is recommended for new devicetrees to
+  specify this property, to keep backwards compatibility a range of 0x00-0xff
+  is assumed if not present)

drivers/pci/host/pcie-designware.c

@@ -500,6 +500,16 @@ int __init dw_pcie_host_init(struct pcie_port *pp)
 		}
 	}
 
+	ret = of_pci_parse_bus_range(np, &pp->busn);
+	if (ret < 0) {
+		pp->busn.name = np->name;
+		pp->busn.start = 0;
+		pp->busn.end = 0xff;
+		pp->busn.flags = IORESOURCE_BUS;
+		dev_dbg(pp->dev, "failed to parse bus-range property: %d, using default %pR\n",
+			ret, &pp->busn);
+	}
+
 	if (!pp->dbi_base) {
 		pp->dbi_base = devm_ioremap(pp->dev, pp->cfg.start,
 					resource_size(&pp->cfg));
@@ -794,6 +804,7 @@ static int dw_pcie_setup(int nr, struct pci_sys_data *sys)
 
 	sys->mem_offset = pp->mem.start - pp->config.mem_bus_addr;
 	pci_add_resource_offset(&sys->resources, &pp->mem, sys->mem_offset);
+	pci_add_resource(&sys->resources, &pp->busn);
 
 	return 1;
 }

drivers/pci/host/pcie-designware.h

@@ -48,6 +48,7 @@ struct pcie_port {
 	struct resource		cfg;
 	struct resource		io;
 	struct resource		mem;
+	struct resource		busn;
 	struct pcie_port_info	config;
 	int			irq;
 	u32			lanes;