[PATCH net 3/3] net: dsa: mv88e6xxx: Link in pcs_get_state() even if LP has AN disabled

["Marek Behún" <kabel@kernel.org>]

Function mv88e6xxx_serdes_pcs_get_state() currently does not report
link up if AN is not complete. This is in contrast to for example the
mvneta's mvneta_mac_pcs_get_state() implementation, where link is simply
taken from link bit.

For 1000base-x and 2500base-x modes, it is possible that the link
partner has autonegotiation disabled. In this case we get zero in the
SPD_DPL_VALID and we won't link, even if we can.

An example of such link partner is Marvell 88X3310 PHY, when put into
the mode where host interface changes between 10gbase-r, 5gbase-r,
2500base-x and sgmii according to copper speed. The 88X3310 does not
enable AN in 2500base-x, and so SerDes on mv88e6xxx currently does not
link with it.

Fix this.

Fixes: a5a6858b793f ("net: dsa: mv88e6xxx: extend phylink to Serdes PHYs")
Signed-off-by: Marek Behún <kabel@kernel.org>
---
 drivers/net/dsa/mv88e6xxx/serdes.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/net/dsa/mv88e6xxx/serdes.c b/drivers/net/dsa/mv88e6xxx/serdes.c
index bc198ef06745..dd3fba7aab99 100644
--- a/drivers/net/dsa/mv88e6xxx/serdes.c
+++ b/drivers/net/dsa/mv88e6xxx/serdes.c
@@ -53,8 +53,11 @@ static int mv88e6xxx_serdes_pcs_get_state(struct mv88e6xxx_chip *chip,
 					  u16 status, u16 lpa,
 					  struct phylink_link_state *state)
 {
-	if (status & MV88E6390_SGMII_PHY_STATUS_SPD_DPL_VALID) {
-		state->link = !!(status & MV88E6390_SGMII_PHY_STATUS_LINK);
+	state->link = !!(status & MV88E6390_SGMII_PHY_STATUS_LINK);
+	state->an_complete = !!(status &
+				MV88E6390_SGMII_PHY_STATUS_SPD_DPL_VALID);
+
+	if (state->an_complete) {
 		state->duplex = status &
 				MV88E6390_SGMII_PHY_STATUS_DUPLEX_FULL ?
 			                         DUPLEX_FULL : DUPLEX_HALF;
@@ -81,8 +84,13 @@ static int mv88e6xxx_serdes_pcs_get_state(struct mv88e6xxx_chip *chip,
 			dev_err(chip->dev, "invalid PHY speed\n");
 			return -EINVAL;
 		}
-	} else {
-		state->link = false;
+	} else if (state->link &&
+		   state->interface != PHY_INTERFACE_MODE_SGMII) {
+		state->duplex = DUPLEX_FULL;
+		if (state->interface == PHY_INTERFACE_MODE_2500BASEX)
+			state->speed = SPEED_2500;
+		else
+			state->speed = SPEED_1000;
 	}
 
 	if (state->interface == PHY_INTERFACE_MODE_2500BASEX)
-- 
2.32.0