PCI: dwc: keystone: Convert .scan_bus() callback to use add_bus

TI keystone is the only Designware driver using .scan_bus(). This
function pointer is the only thing preventing the Designware driver from
using pci_host_probe(). Let's use the pci_ops.add_bus hook instead.

Link: https://lore.kernel.org/r/20200821035420.380495-16-robh@kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Murali Karicheri <m-karicheri2@ti.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/controller/dwc/pci-keystone.c

@@ -454,15 +454,19 @@ static struct pci_ops ks_child_pcie_ops = {
 };
 
 /**
- * ks_pcie_v3_65_scan_bus() - keystone scan_bus post initialization
+ * ks_pcie_v3_65_add_bus() - keystone add_bus post initialization
  *
  * This sets BAR0 to enable inbound access for MSI_IRQ register
  */
-static void ks_pcie_v3_65_scan_bus(struct pcie_port *pp)
+static int ks_pcie_v3_65_add_bus(struct pci_bus *bus)
 {
+	struct pcie_port *pp = bus->sysdata;
 	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
 	struct keystone_pcie *ks_pcie = to_keystone_pcie(pci);
 
+	if (!pci_is_root_bus(bus))
+		return 0;
+
 	/* Configure and set up BAR0 */
 	ks_pcie_set_dbi_mode(ks_pcie);
 
@@ -477,12 +481,15 @@ static void ks_pcie_v3_65_scan_bus(struct pcie_port *pp)
 	  * be sufficient.  Use physical address to avoid any conflicts.
 	  */
 	dw_pcie_writel_dbi(pci, PCI_BASE_ADDRESS_0, ks_pcie->app.start);
+
+	return 0;
 }
 
 static struct pci_ops ks_pcie_ops = {
 	.map_bus = dw_pcie_own_conf_map_bus,
 	.read = pci_generic_config_read,
 	.write = pci_generic_config_write,
+	.add_bus = ks_pcie_v3_65_add_bus,
 };
 
 /**
@@ -842,7 +849,6 @@ static int __init ks_pcie_host_init(struct pcie_port *pp)
 static const struct dw_pcie_host_ops ks_pcie_host_ops = {
 	.host_init = ks_pcie_host_init,
 	.msi_host_init = ks_pcie_msi_host_init,
-	.scan_bus = ks_pcie_v3_65_scan_bus,
 };
 
 static const struct dw_pcie_host_ops ks_pcie_am654_host_ops = {