net: mt7531: only do PLL once after the reset

Move the PLL init of the switch out of the pad configuration of the port
6 (usally cpu port).

Fix a unidirectional 100 mbit limitation on 1 gbit or 2.5 gbit links for
outbound traffic on port 5 or port 6.

Fixes: c288575f ("net: dsa: mt7530: Add the support of MT7531 switch")
Cc: stable@vger.kernel.org
Signed-off-by: Alexander Couzens <lynxis@fe80.eu>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/dsa/mt7530.c

@@ -506,14 +506,19 @@ static bool mt7531_dual_sgmii_supported(struct mt7530_priv *priv)
 static int
 mt7531_pad_setup(struct dsa_switch *ds, phy_interface_t interface)
 {
-	struct mt7530_priv *priv = ds->priv;
+	return 0;
+}
+
+static void
+mt7531_pll_setup(struct mt7530_priv *priv)
+{
 	u32 top_sig;
 	u32 hwstrap;
 	u32 xtal;
 	u32 val;
 
 	if (mt7531_dual_sgmii_supported(priv))
-		return 0;
+		return;
 
 	val = mt7530_read(priv, MT7531_CREV);
 	top_sig = mt7530_read(priv, MT7531_TOP_SIG_SR);
@@ -592,8 +597,6 @@ mt7531_pad_setup(struct dsa_switch *ds, phy_interface_t interface)
 	val |= EN_COREPLL;
 	mt7530_write(priv, MT7531_PLLGP_EN, val);
 	usleep_range(25, 35);
-
-	return 0;
 }
 
 static void
@@ -2331,6 +2334,8 @@ mt7531_setup(struct dsa_switch *ds)
 		     SYS_CTRL_PHY_RST | SYS_CTRL_SW_RST |
 		     SYS_CTRL_REG_RST);
 
+	mt7531_pll_setup(priv);
+
 	if (mt7531_dual_sgmii_supported(priv)) {
 		priv->p5_intf_sel = P5_INTF_SEL_GMAC5_SGMII;
 
@@ -2887,8 +2892,6 @@ mt7531_cpu_port_config(struct dsa_switch *ds, int port)
 	case 6:
 		interface = PHY_INTERFACE_MODE_2500BASEX;
 
-		mt7531_pad_setup(ds, interface);
-
 		priv->p6_interface = interface;
 		break;
 	default: