[PATCH net-next v3 6/6] net: phy: air_an8801: ensure maximum available speed link use

[Louis-Alexis Eyraud <louisalexis.eyraud@collabora.com>]

To ensure that the Airoha AN8801R PHY uses the maximum available link
speed, an additional register write is needed to configure the function
mode for either 1G or 100M/10M operation after link detection.

So, in air_an8801 driver, implement a custom read_status callback, that
after genphy_read_status determines the link speed, sets the bit 0 of
the link mode register (REG_LINK_MODE) if the detected speed is 1Gbps,
or unsets it otherwise.

Signed-off-by: Louis-Alexis Eyraud <louisalexis.eyraud@collabora.com>
---
 drivers/net/phy/air_an8801.c | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/drivers/net/phy/air_an8801.c b/drivers/net/phy/air_an8801.c
index a0f164cbf92b..af46951b1a33 100644
--- a/drivers/net/phy/air_an8801.c
+++ b/drivers/net/phy/air_an8801.c
@@ -964,6 +964,36 @@ static int an8801r_config_init(struct phy_device *phydev)
 	return 0;
 }
 
+static int an8801r_read_status(struct phy_device *phydev)
+{
+	int prev_speed, ret;
+	u32 val;
+
+	prev_speed = phydev->speed;
+
+	ret = genphy_read_status(phydev);
+	if (ret)
+		return ret;
+
+	if (phydev->link && prev_speed != phydev->speed) {
+		/* Ensure that PHY switches to 1G speed when available,
+		 * by configuring the function mode for either 1G or 100M/10M
+		 * operation.
+		 * Therefore, set the link mode register, after read_status
+		 * determines the link speed.
+		 */
+		val = phydev->speed == SPEED_1000 ?
+		      AN8801_BPBUS_LINK_MODE_1000 : 0;
+
+		return an8801_buckpbus_reg_rmw(phydev,
+					       AN8801_BPBUS_REG_LINK_MODE,
+					       AN8801_BPBUS_LINK_MODE_1000,
+					       val);
+	}
+
+	return 0;
+}
+
 static int an8801r_probe(struct phy_device *phydev)
 {
 	struct device *dev = &phydev->mdio.dev;
@@ -1061,6 +1091,7 @@ static struct phy_driver airoha_driver[] = {
 	.suspend		= an8801r_suspend,
 	.resume			= an8801r_resume,
 	.config_aneg		= genphy_config_aneg,
+	.read_status		= an8801r_read_status,
 	.config_intr		= an8801r_config_intr,
 	.handle_interrupt	= an8801r_handle_interrupt,
 	.set_wol		= an8801r_set_wol,

-- 
2.54.0