phy: ti: gmii-sel: Add support for SGMII mode

Add support to configure the CPSW MAC's PHY in SGMII mode if the SoC
supports it. The extra_modes member of the phy_gmii_sel_soc_data struct
corresponding to the SoC is used to determine whether or not the SoC
supports SGMII mode.
Signed-off-by: Siddharth Vadapalli <s-vadapalli@ti.com>
Reviewed-by: Roger Quadros <rogerq@kernel.org>
Link: https://lore.kernel.org/r/20230309063514.398705-2-s-vadapalli@ti.comSigned-off-by: Vinod Koul <vkoul@kernel.org>

drivers/phy/ti/phy-gmii-sel.c

@@ -23,6 +23,7 @@
 #define AM33XX_GMII_SEL_MODE_RGMII	2
 
 /* J72xx SoC specific definitions for the CONTROL port */
+#define J72XX_GMII_SEL_MODE_SGMII	3
 #define J72XX_GMII_SEL_MODE_QSGMII	4
 #define J72XX_GMII_SEL_MODE_QSGMII_SUB	6
 
@@ -106,6 +107,13 @@ static int phy_gmii_sel_mode(struct phy *phy, enum phy_mode mode, int submode)
 			gmii_sel_mode = J72XX_GMII_SEL_MODE_QSGMII_SUB;
 		break;
 
+	case PHY_INTERFACE_MODE_SGMII:
+		if (!(soc_data->extra_modes & BIT(PHY_INTERFACE_MODE_SGMII)))
+			goto unsupported;
+		else
+			gmii_sel_mode = J72XX_GMII_SEL_MODE_SGMII;
+		break;
+
 	default:
 		goto unsupported;
 	}