net: phylink: add support for disabling in-band-status for base-x

MediaTek LynxI PCS, 2500Base-X will only work without inband status due to
hardware limitation.

I understand this patch probably will not get approved as it is now, but
perhaps with some pointers in the correct direction to follow, I can change
it so it could be. It does however get the result that the rtl8221b on a
sfp module functions correctly, with and without (as optical sfp) the phy
attached and without using a sfp-quirk/ethtool to disable auto-negotiation.

Introduce bool phylink_basex_no_inband(pl), a function similar to
bool phylink_phy_no_inband(phy). An option could be to use a function like
bool pcs->ops->basex_no_inband(interface), where if the function-pointer is
null, it means it is supported. This instead of using the
of_device_is_compatible() function.

Code changed in phylink_pcs_neg_mode():

When there is no PHY attached, pl->pcs_neg_mode is set to
PHYLINK_PCS_NEG_INBAND_DISABLED. link_config is changed:
- advertising ETHTOOL_LINK_MODE_Autoneg_BIT cleared
- speed set according to interface
- duplex to DUPLEX_FULL
- pause to MLO_PAUSE_NONE

When there is a PHY attached, pl->cur_link_an_mode is set to MLO_AN_PHY.
To have the pcs function correctly with the rtl8221b, we need to do the
following to the in-band-status. We need to disable it when interface of
the pcs is set to 2500base-x, but need it enable it when switched to sgmii.

Changes to be committed:
	modified:   drivers/net/phy/phylink.c

Signed-off-by: Eric Woudstra <ericwouds@gmail.com>

drivers/net/phy/phylink.c

@@ -1074,6 +1074,20 @@ static void phylink_pcs_an_restart(struct phylink *pl)
 		pl->pcs->ops->pcs_an_restart(pl->pcs);
 }
 
+/* This function needs to be changed, not using compatible */
+static bool phylink_basex_no_inband(struct phylink *pl)
+{
+	struct device_node *node = pl->config->dev->of_node;
+
+	if (!node)
+		return false;
+
+	if (!of_device_is_compatible(node, "mediatek,eth-mac"))
+		return false;
+
+	return true;
+}
+
 /**
  * phylink_pcs_neg_mode() - helper to determine PCS inband mode
  * @mode: one of %MLO_AN_FIXED, %MLO_AN_PHY, %MLO_AN_INBAND.
@@ -1093,11 +1107,24 @@ static void phylink_pcs_an_restart(struct phylink *pl)
  * Note: this is for cases where the PCS itself is involved in negotiation
  * (e.g. Clause 37, SGMII and similar) not Clause 73.
  */
-static unsigned int phylink_pcs_neg_mode(unsigned int mode,
-					 phy_interface_t interface,
-					 const unsigned long *advertising)
+static void phylink_pcs_neg_mode(struct phylink *pl,
+				 phy_interface_t interface,
+				 const unsigned long *advertising)
 {
-	unsigned int neg_mode;
+	if ((!!pl->phydev) && phylink_basex_no_inband(pl)) {
+		switch (interface) {
+		case PHY_INTERFACE_MODE_1000BASEX:
+		case PHY_INTERFACE_MODE_2500BASEX:
+			if (pl->cur_link_an_mode == MLO_AN_INBAND)
+				pl->cur_link_an_mode = MLO_AN_PHY;
+			break;
+		default:
+			/* restore mode if it was changed before */
+			if (pl->cur_link_an_mode == MLO_AN_PHY &&
+			    pl->cfg_link_an_mode == MLO_AN_INBAND)
+				pl->cur_link_an_mode = pl->cfg_link_an_mode;
+		}
+	}
 
 	switch (interface) {
 	case PHY_INTERFACE_MODE_SGMII:
@@ -1109,10 +1136,10 @@ static unsigned int phylink_pcs_neg_mode(unsigned int mode,
 		 * inband communication. Note: there exist PHYs that run
 		 * with SGMII but do not send the inband data.
 		 */
-		if (!phylink_autoneg_inband(mode))
-			neg_mode = PHYLINK_PCS_NEG_OUTBAND;
+		if (!phylink_autoneg_inband(pl->cur_link_an_mode))
+			pl->pcs_neg_mode = PHYLINK_PCS_NEG_OUTBAND;
 		else
-			neg_mode = PHYLINK_PCS_NEG_INBAND_ENABLED;
+			pl->pcs_neg_mode = PHYLINK_PCS_NEG_INBAND_ENABLED;
 		break;
 
 	case PHY_INTERFACE_MODE_1000BASEX:
@@ -1123,21 +1150,30 @@ static unsigned int phylink_pcs_neg_mode(unsigned int mode,
 		 * as well, but drivers may not support this, so may
 		 * need to override this.
 		 */
-		if (!phylink_autoneg_inband(mode))
-			neg_mode = PHYLINK_PCS_NEG_OUTBAND;
-		else if (linkmode_test_bit(ETHTOOL_LINK_MODE_Autoneg_BIT,
-					   advertising))
-			neg_mode = PHYLINK_PCS_NEG_INBAND_ENABLED;
-		else
-			neg_mode = PHYLINK_PCS_NEG_INBAND_DISABLED;
+		if (!phylink_autoneg_inband(pl->cur_link_an_mode)) {
+			pl->pcs_neg_mode = PHYLINK_PCS_NEG_OUTBAND;
+		} else if (linkmode_test_bit(ETHTOOL_LINK_MODE_Autoneg_BIT,
+					   advertising) &&
+				!phylink_basex_no_inband(pl)) {
+			pl->pcs_neg_mode = PHYLINK_PCS_NEG_INBAND_ENABLED;
+		} else {
+			pl->pcs_neg_mode = PHYLINK_PCS_NEG_INBAND_DISABLED;
+			linkmode_clear_bit(ETHTOOL_LINK_MODE_Autoneg_BIT,
+					   pl->link_config.advertising);
+			pl->link_config.speed = (interface ==
+						 PHY_INTERFACE_MODE_1000BASEX) ?
+						 SPEED_1000 : SPEED_2500;
+			pl->link_config.duplex = DUPLEX_FULL;
+			pl->link_config.pause = MLO_PAUSE_NONE; /* ????? */
+		}
 		break;
 
 	default:
-		neg_mode = PHYLINK_PCS_NEG_NONE;
+		pl->pcs_neg_mode = PHYLINK_PCS_NEG_NONE;
 		break;
 	}
 
-	return neg_mode;
+	return;
 }
 
 static void phylink_major_config(struct phylink *pl, bool restart,
@@ -1151,9 +1187,7 @@ static void phylink_major_config(struct phylink *pl, bool restart,
 
 	phylink_dbg(pl, "major config %s\n", phy_modes(state->interface));
 
-	pl->pcs_neg_mode = phylink_pcs_neg_mode(pl->cur_link_an_mode,
-						state->interface,
-						state->advertising);
+	phylink_pcs_neg_mode(pl, state->interface, state->advertising);
 
 	if (pl->using_mac_select_pcs) {
 		pcs = pl->mac_ops->mac_select_pcs(pl->config, state->interface);
@@ -1257,9 +1291,8 @@ static int phylink_change_inband_advert(struct phylink *pl)
 		    pl->link_config.pause);
 
 	/* Recompute the PCS neg mode */
-	pl->pcs_neg_mode = phylink_pcs_neg_mode(pl->cur_link_an_mode,
-					pl->link_config.interface,
-					pl->link_config.advertising);
+	phylink_pcs_neg_mode(pl, pl->link_config.interface,
+			     pl->link_config.advertising);
 
 	neg_mode = pl->cur_link_an_mode;
 	if (pl->pcs->neg_mode)