Reset PCS state when changing interface mode.

Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Tested-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
---
 drivers/net/ethernet/mediatek/mtk_eth_soc.h | 4 ++++
 drivers/net/ethernet/mediatek/mtk_sgmii.c   | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.h b/drivers/net/ethernet/mediatek/mtk_eth_soc.h
index 7014c02ba2d4d..142def8629c82 100644
--- a/drivers/net/ethernet/mediatek/mtk_eth_soc.h
+++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.h
@@ -548,6 +548,10 @@
 #define SGMII_SEND_AN_ERROR_EN		BIT(11)
 #define SGMII_IF_MODE_MASK		GENMASK(5, 1)
 
+/* Register to reset SGMII design */
+#define SGMII_RESERVED_0	0x34
+#define SGMII_SW_RESET		BIT(0)
+
 /* Register to set SGMII speed, ANA RG_ Control Signals III*/
 #define SGMSYS_ANA_RG_CS3	0x2028
 #define RG_PHY_SPEED_MASK	(BIT(2) | BIT(3))
diff --git a/drivers/net/ethernet/mediatek/mtk_sgmii.c b/drivers/net/ethernet/mediatek/mtk_sgmii.c
index d7ffaaeaf9ab5..d7e7352041a4f 100644
--- a/drivers/net/ethernet/mediatek/mtk_sgmii.c
+++ b/drivers/net/ethernet/mediatek/mtk_sgmii.c
@@ -88,6 +88,10 @@ static int mtk_pcs_config(struct phylink_pcs *pcs, unsigned int mode,
 		regmap_update_bits(mpcs->regmap, SGMSYS_QPHY_PWR_STATE_CTRL,
 				   SGMII_PHYA_PWD, SGMII_PHYA_PWD);
 
+		/* Reset SGMII PCS state */
+		regmap_update_bits(mpcs->regmap, SGMII_RESERVED_0,
+				   SGMII_SW_RESET, SGMII_SW_RESET);
+
 		if (mpcs->flags & MTK_SGMII_FLAG_PN_SWAP)
 			regmap_update_bits(mpcs->regmap, SGMSYS_QPHY_WRAP_CTRL,
 					   SGMII_PN_SWAP_MASK,
-- 
2.39.2