amd-xgbe: Set the MII control width for the MAC interface

When running in SGMII mode at speeds below 1000Mbps, the auto-negotition
control register must set the MII control width for the MAC interface
to be 8-bits wide.  By default the width is 4-bits.
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/amd/xgbe/xgbe-common.h

@@ -1339,6 +1339,7 @@
 #define XGBE_AN_CL37_PCS_MODE_BASEX	0x00
 #define XGBE_AN_CL37_PCS_MODE_SGMII	0x04
 #define XGBE_AN_CL37_TX_CONFIG_MASK	0x08
+#define XGBE_AN_CL37_MII_CTRL_8BIT	0x0100
 
 /* Bit setting and getting macros
  *  The get macro will extract the current bit field value from within

drivers/net/ethernet/amd/xgbe/xgbe-mdio.c

@@ -982,6 +982,8 @@ static void xgbe_an37_init(struct xgbe_prv_data *pdata)
 		break;
 	}
 
+	reg |= XGBE_AN_CL37_MII_CTRL_8BIT;
+
 	XMDIO_WRITE(pdata, MDIO_MMD_VEND2, MDIO_VEND2_AN_CTRL, reg);
 
 	netif_dbg(pdata, link, pdata->netdev, "CL37 AN (%s) initialized\n",