From 611e2dabb4b3243d176739fd6a5a34d007fa3f86 Mon Sep 17 00:00:00 2001
From: Daniel Golle <daniel@makrotopia.org>
Date: Tue, 14 Mar 2023 00:34:26 +0000
Subject: [PATCH 1/2] net: ethernet: mtk_eth_soc: reset PCS state
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Reset the internal PCS state machine when changing interface mode.
This prevents confusing the state machine when changing interface
modes, e.g. from SGMII to 2500Base-X or vice-versa.

Fixes: 7e538372694b ("net: ethernet: mediatek: Re-add support SGMII")
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>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
 drivers/net/ethernet/mediatek/mtk_eth_soc.h | 4 ++++
 drivers/net/ethernet/mediatek/mtk_sgmii.c   | 4 ++++
 2 files changed, 8 insertions(+)

--- a/drivers/net/ethernet/mediatek/mtk_eth_soc.h
+++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.h
@@ -542,6 +542,10 @@
 #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))
--- 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
 		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 (interface == PHY_INTERFACE_MODE_2500BASEX)
 			rgc3 = RG_PHY_SPEED_3_125G;
 		else
