[RFC PATCH net-next 4/8] net: phy: realtek: disable SGMII in-band AN for 2.5G PHYs

[Daniel Golle]

MAC drivers don't use SGMII in-band autonegotiation unless told to do so
in device tree using 'managed = "in-band-status"'. When using MDIO to
access a PHY, in-band-status is unneeded as we have link-status via
MDIO. Switch off SGMII in-band autonegotiation using magic values.

Reported-by: Chen Minqiang <ptpt52@xxxxxxxxx>
Reported-by: Chukun Pan <amadeus@xxxxxxxxxx>
Reported-by: Yevhen Kolomeiko <jarvis2709@xxxxxxxxx>
Tested-by: Yevhen Kolomeiko <jarvis2709@xxxxxxxxx>
Signed-off-by: Daniel Golle <daniel@xxxxxxxxxxxxxx>
---
 drivers/net/phy/realtek.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/net/phy/realtek.c b/drivers/net/phy/realtek.c
index 9b477dd17fa56..f97b5e49fae58 100644
--- a/drivers/net/phy/realtek.c
+++ b/drivers/net/phy/realtek.c
@@ -883,6 +883,7 @@ static irqreturn_t rtl9000a_handle_interrupt(struct phy_device *phydev)
 static int rtl8221b_config_init(struct phy_device *phydev)
 {
 	u16 option_mode;
+	int val;
 
 	switch (phydev->interface) {
 	case PHY_INTERFACE_MODE_2500BASEX:
@@ -919,6 +920,13 @@ static int rtl8221b_config_init(struct phy_device *phydev)
 		break;
 	}
 
+	/* Disable SGMII AN */
+	phy_write_mmd(phydev, RTL8221B_MMD_SERDES_CTRL, 0x7588, 0x2);
+	phy_write_mmd(phydev, RTL8221B_MMD_SERDES_CTRL, 0x7589, 0x71d0);
+	phy_write_mmd(phydev, RTL8221B_MMD_SERDES_CTRL, 0x7587, 0x3);
+	phy_read_mmd_poll_timeout(phydev, RTL8221B_MMD_SERDES_CTRL, 0x7587,
+				  val, !(val & BIT(0)), 500, 100000, false);
+
 	return 0;
 }
 
-- 
2.40.0