driver/net/fm/memac_phy: set NEG bit for external MDIOs

NEG bit default is '1' for external MDIOs as per FMAN-v3 RM, but on some
platforms, e.g. T2080QDS, this bit is '0', which leads to MDIO failure
on XAUI PHY, so set this bit definitely to align with the RM.

Signed-off-by: Shaohui Xie <Shaohui.Xie@freescale.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
Reviewed-by: York Sun <yorksun@freescale.com>

arch/powerpc/include/asm/fsl_memac.h

@@ -244,6 +244,7 @@ struct memac_mdio_controller {
 #define MDIO_STAT_PRE		(1 << 5)
 #define MDIO_STAT_ENC		(1 << 6)
 #define MDIO_STAT_HOLD_15_CLK	(7 << 2)
+#define MDIO_STAT_NEG		(1 << 23)
 
 #define MDIO_CTL_DEV_ADDR(x)	(x & 0x1f)
 #define MDIO_CTL_PORT_ADDR(x)	((x & 0x1f) << 5)

drivers/net/fm/memac_phy.c

@@ -139,9 +139,12 @@ int fm_memac_mdio_init(bd_t *bis, struct memac_mdio_info *info)
 	 * is zero, so MDIO clock is disabled.
 	 * So, for proper functioning of MDIO, MDIO_CLK_DIV bits needs to
 	 * be properly initialized.
+	 * NEG bit default should be '1' as per FMAN-v3 RM, but on platform
+	 * like T2080QDS, this bit default is '0', which leads to MDIO failure
+	 * on XAUI PHY, so set this bit definitely.
 	 */
 	setbits_be32(&((struct memac_mdio_controller *)info->regs)->mdio_stat,
-		     MDIO_STAT_CLKDIV(258));
+		     MDIO_STAT_CLKDIV(258) | MDIO_STAT_NEG);
 
 	return mdio_register(bus);
 }