This code is from before this driver was converted to phylink API. Phylink
deals with the unsupported interface cases before mt7530_setup_port6() is
run. Therefore, the default case would never run. However, it must be
defined nonetheless to handle all the remaining enumeration values, the
phy-modes.

Switch to if statement for RGMII and return which simplifies the code and
saves an indent.

Do not set P6_INTF_MODE, which is the the three least significant bits of
the MT7530_P6ECR register, to 0 for RGMII as it will already be 0 after
reset.

Read XTAL after checking for RGMII as it's only needed for the TRGMII
interface mode.

Change mt7530_setup_port6() to void now that there're no error cases left.

Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com>
---
 drivers/net/dsa/mt7530.c | 100 ++++++++++++++++-----------------------
 1 file changed, 40 insertions(+), 60 deletions(-)

diff --git a/drivers/net/dsa/mt7530.c b/drivers/net/dsa/mt7530.c
index 2608b09d3295..f36f240231b5 100644
--- a/drivers/net/dsa/mt7530.c
+++ b/drivers/net/dsa/mt7530.c
@@ -414,72 +414,56 @@ mt753x_preferred_default_local_cpu_port(struct dsa_switch *ds)
 }
 
 /* Setup port 6 interface mode and TRGMII TX circuit */
-static int
+static void
 mt7530_setup_port6(struct dsa_switch *ds, phy_interface_t interface)
 {
 	struct mt7530_priv *priv = ds->priv;
-	u32 ncpo1, ssc_delta, trgint, xtal;
+	u32 ncpo1, ssc_delta, xtal;
 
 	mt7530_clear(priv, MT7530_MHWTRAP, MHWTRAP_P6_DIS);
 
+	if (interface == PHY_INTERFACE_MODE_RGMII)
+		return;
+
+	mt7530_rmw(priv, MT7530_P6ECR, P6_INTF_MODE_MASK, P6_INTF_MODE(1));
+
 	xtal = mt7530_read(priv, MT7530_MHWTRAP) & HWTRAP_XTAL_MASK;
 
-	switch (interface) {
-	case PHY_INTERFACE_MODE_RGMII:
-		trgint = 0;
-		break;
-	case PHY_INTERFACE_MODE_TRGMII:
-		trgint = 1;
+	if (xtal == HWTRAP_XTAL_25MHZ)
+		ssc_delta = 0x57;
+	else
+		ssc_delta = 0x87;
+
+	if (priv->id == ID_MT7621) {
+		/* PLL frequency: 125MHz: 1.0GBit */
+		if (xtal == HWTRAP_XTAL_40MHZ)
+			ncpo1 = 0x0640;
 		if (xtal == HWTRAP_XTAL_25MHZ)
-			ssc_delta = 0x57;
-		else
-			ssc_delta = 0x87;
-		if (priv->id == ID_MT7621) {
-			/* PLL frequency: 125MHz: 1.0GBit */
-			if (xtal == HWTRAP_XTAL_40MHZ)
-				ncpo1 = 0x0640;
-			if (xtal == HWTRAP_XTAL_25MHZ)
-				ncpo1 = 0x0a00;
-		} else { /* PLL frequency: 250MHz: 2.0Gbit */
-			if (xtal == HWTRAP_XTAL_40MHZ)
-				ncpo1 = 0x0c80;
-			if (xtal == HWTRAP_XTAL_25MHZ)
-				ncpo1 = 0x1400;
-		}
-		break;
-	default:
-		dev_err(priv->dev, "xMII interface %d not supported\n",
-			interface);
-		return -EINVAL;
+			ncpo1 = 0x0a00;
+	} else { /* PLL frequency: 250MHz: 2.0Gbit */
+		if (xtal == HWTRAP_XTAL_40MHZ)
+			ncpo1 = 0x0c80;
+		if (xtal == HWTRAP_XTAL_25MHZ)
+			ncpo1 = 0x1400;
 	}
 
-	mt7530_rmw(priv, MT7530_P6ECR, P6_INTF_MODE_MASK,
-		   P6_INTF_MODE(trgint));
-
-	if (trgint) {
-		/* Disable the MT7530 TRGMII clocks */
-		core_clear(priv, CORE_TRGMII_GSW_CLK_CG, REG_TRGMIICK_EN);
-
-		/* Setup the MT7530 TRGMII Tx Clock */
-		core_write(priv, CORE_PLL_GROUP5, RG_LCDDS_PCW_NCPO1(ncpo1));
-		core_write(priv, CORE_PLL_GROUP6, RG_LCDDS_PCW_NCPO0(0));
-		core_write(priv, CORE_PLL_GROUP10, RG_LCDDS_SSC_DELTA(ssc_delta));
-		core_write(priv, CORE_PLL_GROUP11, RG_LCDDS_SSC_DELTA1(ssc_delta));
-		core_write(priv, CORE_PLL_GROUP4,
-			   RG_SYSPLL_DDSFBK_EN | RG_SYSPLL_BIAS_EN |
-			   RG_SYSPLL_BIAS_LPF_EN);
-		core_write(priv, CORE_PLL_GROUP2,
-			   RG_SYSPLL_EN_NORMAL | RG_SYSPLL_VODEN |
-			   RG_SYSPLL_POSDIV(1));
-		core_write(priv, CORE_PLL_GROUP7,
-			   RG_LCDDS_PCW_NCPO_CHG | RG_LCCDS_C(3) |
-			   RG_LCDDS_PWDB | RG_LCDDS_ISO_EN);
+	/* Disable the MT7530 TRGMII clocks */
+	core_clear(priv, CORE_TRGMII_GSW_CLK_CG, REG_TRGMIICK_EN);
 
-		/* Enable the MT7530 TRGMII clocks */
-		core_set(priv, CORE_TRGMII_GSW_CLK_CG, REG_TRGMIICK_EN);
-	}
+	/* Setup the MT7530 TRGMII Tx Clock */
+	core_write(priv, CORE_PLL_GROUP5, RG_LCDDS_PCW_NCPO1(ncpo1));
+	core_write(priv, CORE_PLL_GROUP6, RG_LCDDS_PCW_NCPO0(0));
+	core_write(priv, CORE_PLL_GROUP10, RG_LCDDS_SSC_DELTA(ssc_delta));
+	core_write(priv, CORE_PLL_GROUP11, RG_LCDDS_SSC_DELTA1(ssc_delta));
+	core_write(priv, CORE_PLL_GROUP4, RG_SYSPLL_DDSFBK_EN |
+		   RG_SYSPLL_BIAS_EN | RG_SYSPLL_BIAS_LPF_EN);
+	core_write(priv, CORE_PLL_GROUP2, RG_SYSPLL_EN_NORMAL |
+		   RG_SYSPLL_VODEN | RG_SYSPLL_POSDIV(1));
+	core_write(priv, CORE_PLL_GROUP7, RG_LCDDS_PCW_NCPO_CHG |
+		   RG_LCCDS_C(3) | RG_LCDDS_PWDB | RG_LCDDS_ISO_EN);
 
-	return 0;
+	/* Enable the MT7530 TRGMII clocks */
+	core_set(priv, CORE_TRGMII_GSW_CLK_CG, REG_TRGMIICK_EN);
 }
 
 static void
@@ -2597,15 +2581,11 @@ mt7530_mac_config(struct dsa_switch *ds, int port, unsigned int mode,
 		  phy_interface_t interface)
 {
 	struct mt7530_priv *priv = ds->priv;
-	int ret;
 
-	if (port == 5) {
+	if (port == 5)
 		mt7530_setup_port5(priv->ds, interface);
-	} else if (port == 6) {
-		ret = mt7530_setup_port6(priv->ds, interface);
-		if (ret)
-			return ret;
-	}
+	else if (port == 6)
+		mt7530_setup_port6(priv->ds, interface);
 
 	return 0;
 }
-- 
2.40.1