ravb: Add RZ/G2L MII interface support

EMAC IP found on RZ/G2L Gb ethernet supports MII interface.
This patch adds support for selecting MII interface mode.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Link: https://lore.kernel.org/r/20220914192604.265859-1-biju.das.jz@bp.renesas.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/renesas/ravb.h

@@ -189,6 +189,7 @@ enum ravb_reg {
 	PSR	= 0x0528,
 	PIPR	= 0x052c,
 	CXR31	= 0x0530,	/* RZ/G2L only */
+	CXR35	= 0x0540,	/* RZ/G2L only */
 	MPR	= 0x0558,
 	PFTCR	= 0x055c,
 	PFRCR	= 0x0560,
@@ -965,6 +966,13 @@ enum CXR31_BIT {
 	CXR31_SEL_LINK1	= 0x00000008,
 };
 
+enum CXR35_BIT {
+	CXR35_SEL_XMII		= 0x00000003,
+	CXR35_SEL_XMII_RGMII	= 0x00000000,
+	CXR35_SEL_XMII_MII	= 0x00000002,
+	CXR35_HALFCYC_CLKSW	= 0xffff0000,
+};
+
 enum CSR0_BIT {
 	CSR0_TPE	= 0x00000010,
 	CSR0_RPE	= 0x00000020,

drivers/net/ethernet/renesas/ravb_main.c

@@ -540,7 +540,13 @@ static void ravb_emac_init_gbeth(struct net_device *ndev)
 	/* E-MAC interrupt enable register */
 	ravb_write(ndev, ECSIPR_ICDIP, ECSIPR);
 
-	ravb_modify(ndev, CXR31, CXR31_SEL_LINK0 | CXR31_SEL_LINK1, CXR31_SEL_LINK0);
+	if (priv->phy_interface == PHY_INTERFACE_MODE_MII) {
+		ravb_modify(ndev, CXR31, CXR31_SEL_LINK0 | CXR31_SEL_LINK1, 0);
+		ravb_write(ndev, (1000 << 16) | CXR35_SEL_XMII_MII, CXR35);
+	} else {
+		ravb_modify(ndev, CXR31, CXR31_SEL_LINK0 | CXR31_SEL_LINK1,
+			    CXR31_SEL_LINK0);
+	}
 }
 
 static void ravb_emac_init_rcar(struct net_device *ndev)