ramips: mt7620: add ephy-disable option to switch driver

Add back the register write to disable internal PHYs
as a separate option in the code that can be set using a DTS property.

Set the option to true by default
when an external mt7530 switch is identified.

This makes the driver more in sync with original SDK code
while keeping the lines separated into different options
to accommodate any board with any PHY layout.

Signed-off-by: Michael Pratt <mcpratt@pm.me>

target/linux/ramips/files/drivers/net/ethernet/ralink/gsw_mt7620.c

@@ -73,7 +73,13 @@ static void mt7620_hw_init(struct mt7620_gsw *gsw)
 	/* Enable MIB stats */
 	mtk_switch_w32(gsw, mtk_switch_r32(gsw, GSW_REG_MIB_CNT_EN) | (1 << 1), GSW_REG_MIB_CNT_EN);
 
-	if (gsw->ephy_base) {
+	if (gsw->ephy_disable) {
+		mtk_switch_w32(gsw, mtk_switch_r32(gsw, GSW_REG_GPC1) |
+			(gsw->ephy_base << 16) | (0x1f << 24),
+			GSW_REG_GPC1);
+
+		pr_info("gsw: internal ephy disabled\n");
+	} else if (gsw->ephy_base) {
 		mtk_switch_w32(gsw, mtk_switch_r32(gsw, GSW_REG_GPC1) |
 			(gsw->ephy_base << 16),
 			GSW_REG_GPC1);
@@ -194,13 +200,17 @@ int mtk_gsw_init(struct fe_priv *priv)
 	gsw = platform_get_drvdata(pdev);
 	priv->soc->swpriv = gsw;
 
+	gsw->ephy_disable = of_property_read_bool(np, "mediatek,ephy-disable");
+
 	mdiobus_node = of_get_child_by_name(eth_node, "mdio-bus");
 	if (mdiobus_node) {
 		for_each_child_of_node(mdiobus_node, phy_node) {
 			id = of_get_property(phy_node, "reg", NULL);
 			if (id && (be32_to_cpu(*id) == 0x1f))
-				of_node_put(mdiobus_node);
+				gsw->ephy_disable = true;
 		}
+
+		of_node_put(mdiobus_node);
 	}
 
 	gsw->port4_ephy = !of_property_read_bool(np, "mediatek,port4-gmac");

target/linux/ramips/files/drivers/net/ethernet/ralink/gsw_mt7620.h

@@ -92,6 +92,7 @@ struct mt7620_gsw {
 	struct device		*dev;
 	void __iomem		*base;
 	int			irq;
+	bool			ephy_disable;
 	bool			port4_ephy;
 	unsigned long int	autopoll;
 	u16			ephy_base;