net: phylink: Support disabling autonegotiation for PCS

The auto-negotiation state in the PCS as set by
phylink_mii_c22_pcs_config was previously always enabled when the
driver is configured for in-band autonegotiation, even if
autonegotiation was disabled on the interface with ethtool. Update the
code to set the BMCR_ANENABLE bit based on the interface's
autonegotiation enabled state.

Update phylink_mii_c22_pcs_get_state to not check
autonegotiation-related fields when autonegotiation is disabled.

Update phylink_mac_pcs_get_state to initialize the state based on the
interface's configured speed, duplex and pause parameters rather than
to unknown when autonegotiation is disabled, before calling the
driver's pcs_get_state functions, as they are not likely to provide
meaningful data for these fields when autonegotiation is disabled. In
this case the driver is really just filling in the link state field.

Note that in cases where there is a downstream PHY connected, such as
with SGMII and a copper PHY, the configuration set by ethtool is
handled by phy_ethtool_ksettings_set and not propagated to the PCS.
This is correct since SGMII or 1000Base-X autonegotiation with the PCS
should normally still be used even if the copper side has disabled it.

Signed-off-by: Robert Hancock <robert.hancock@calian.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/phylink.c

@@ -551,9 +551,15 @@ static void phylink_mac_pcs_get_state(struct phylink *pl,
 	linkmode_zero(state->lp_advertising);
 	state->interface = pl->link_config.interface;
 	state->an_enabled = pl->link_config.an_enabled;
-	state->speed = SPEED_UNKNOWN;
-	state->duplex = DUPLEX_UNKNOWN;
-	state->pause = MLO_PAUSE_NONE;
+	if  (state->an_enabled) {
+		state->speed = SPEED_UNKNOWN;
+		state->duplex = DUPLEX_UNKNOWN;
+		state->pause = MLO_PAUSE_NONE;
+	} else {
+		state->speed =  pl->link_config.speed;
+		state->duplex = pl->link_config.duplex;
+		state->pause = pl->link_config.pause;
+	}
 	state->an_complete = 0;
 	state->link = 1;
 
@@ -2549,7 +2555,10 @@ void phylink_mii_c22_pcs_get_state(struct mdio_device *pcs,
 
 	state->link = !!(bmsr & BMSR_LSTATUS);
 	state->an_complete = !!(bmsr & BMSR_ANEGCOMPLETE);
-	if (!state->link)
+	/* If there is no link or autonegotiation is disabled, the LP advertisement
+	 * data is not meaningful, so don't go any further.
+	 */
+	if (!state->link || !state->an_enabled)
 		return;
 
 	switch (state->interface) {
@@ -2651,7 +2660,12 @@ int phylink_mii_c22_pcs_config(struct mdio_device *pcs, unsigned int mode,
 	changed = ret > 0;
 
 	/* Ensure ISOLATE bit is disabled */
-	bmcr = mode == MLO_AN_INBAND ? BMCR_ANENABLE : 0;
+	if (mode == MLO_AN_INBAND &&
+	    linkmode_test_bit(ETHTOOL_LINK_MODE_Autoneg_BIT, advertising))
+		bmcr = BMCR_ANENABLE;
+	else
+		bmcr = 0;
+
 	ret = mdiobus_modify(pcs->bus, pcs->addr, MII_BMCR,
 			     BMCR_ANENABLE | BMCR_ISOLATE, bmcr);
 	if (ret < 0)