PCI: dwc: Add a default pci_ops.map_bus for root port

The Designware root port config space is memory mapped accesses via the
DBI space by default. Add a common implementation
dw_pcie_own_conf_map_bus() for platforms to use.

Link: https://lore.kernel.org/r/20200821035420.380495-5-robh@kernel.orgSigned-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Jingoo Han <jingoohan1@gmail.com>
Cc: Gustavo Pimentel <gustavo.pimentel@synopsys.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/controller/dwc/pcie-designware-host.c

@@ -602,6 +602,18 @@ static int dw_pcie_wr_conf(struct pci_bus *bus, u32 devfn,
 	return dw_pcie_wr_other_conf(pp, bus, devfn, where, size, val);
 }
 
+void __iomem *dw_pcie_own_conf_map_bus(struct pci_bus *bus, unsigned int devfn, int where)
+{
+	struct pcie_port *pp = bus->sysdata;
+	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
+
+	if (PCI_SLOT(devfn) > 0)
+		return NULL;
+
+	return pci->dbi_base + where;
+}
+EXPORT_SYMBOL_GPL(dw_pcie_own_conf_map_bus);
+
 static struct pci_ops dw_pcie_ops = {
 	.read = dw_pcie_rd_conf,
 	.write = dw_pcie_wr_conf,

drivers/pci/controller/dwc/pcie-designware.h

@@ -377,6 +377,8 @@ void dw_pcie_setup_rc(struct pcie_port *pp);
 int dw_pcie_host_init(struct pcie_port *pp);
 void dw_pcie_host_deinit(struct pcie_port *pp);
 int dw_pcie_allocate_domains(struct pcie_port *pp);
+void __iomem *dw_pcie_own_conf_map_bus(struct pci_bus *bus, unsigned int devfn,
+				       int where);
 #else
 static inline irqreturn_t dw_handle_msi_irq(struct pcie_port *pp)
 {
@@ -408,6 +410,12 @@ static inline int dw_pcie_allocate_domains(struct pcie_port *pp)
 {
 	return 0;
 }
+static inline void __iomem *dw_pcie_own_conf_map_bus(struct pci_bus *bus,
+						     unsigned int devfn,
+						     int where)
+{
+	return NULL;
+}
 #endif
 
 #ifdef CONFIG_PCIE_DW_EP