kernel: b53: force BCM531x5 port 5 link state if enabled

Some devices (e.g. Tenda AC9 based on BCM47189B0) have BCM53125 with
port 5 connected to the second Ethernet interface on the SoC. In such
case there is no PHY and we need to force link manually.

This assumes port 5 can be marked as enabled for such devices. It's not
implemented yet unfortunately.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>

target/linux/generic/files/drivers/net/phy/b53/b53_common.c

@@ -534,6 +534,19 @@ static int b53_switch_reset(struct b53_device *dev)
 		b53_write8(dev, B53_CTRL_PAGE, B53_PORT_OVERRIDE_CTRL,
 			   mii_port_override | PORT_OVERRIDE_EN |
 			   PORT_OVERRIDE_LINK);
+
+		/* BCM47189 has another interface connected to the port 5 */
+		if (dev->enabled_ports & BIT(5)) {
+			u8 po_reg = B53_GMII_PORT_OVERRIDE_CTRL(5);
+			u8 gmii_po;
+
+			b53_read8(dev, B53_CTRL_PAGE, po_reg, &gmii_po);
+			gmii_po |= GMII_PO_LINK |
+				   GMII_PO_RX_FLOW |
+				   GMII_PO_TX_FLOW |
+				   GMII_PO_EN;
+			b53_write8(dev, B53_CTRL_PAGE, po_reg, gmii_po);
+		}
 	} else if (is5301x(dev)) {
 		if (cpu_port == 8) {
 			u8 mii_port_override;