From 2213918077f361c58d2380525a92ead2875e99dd Mon Sep 17 00:00:00 2001
From: "Russell King (Oracle)" <rmk+kernel@armlinux.org.uk>
Date: Mon, 4 Mar 2024 15:33:01 +0000
Subject: net: phylink: expand phylink_pcs_neg_mode()

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
---
 drivers/net/phy/phylink.c | 105 +++++++++++++++++++++++++++++++++++++---------
 1 file changed, 86 insertions(+), 19 deletions(-)

diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
index 3f92941e227e..33ada56918d7 100644
--- a/drivers/net/phy/phylink.c
+++ b/drivers/net/phy/phylink.c
@@ -1185,12 +1185,10 @@ static unsigned int phylink_pcs_neg_mode(struct phylink *pl,
 	unsigned int phy_link_mode = 0;
 	unsigned int pcs_link_mode;
 	unsigned int neg_mode;
-
-	if (phylink_autoneg_inband(mode)) {
-		pcs_link_mode = phylink_pcs_query_inband(pcs, interface);
-		if (pl->phydev)
-			phy_link_mode = phy_query_inband(pl->phydev, interface);
-	}
+	enum {
+		INBAND_CISCO_SGMII,
+		INBAND_8023Z,
+	} type;
 
 	switch (interface) {
 	case PHY_INTERFACE_MODE_SGMII:
@@ -1202,10 +1200,7 @@ static unsigned int phylink_pcs_neg_mode(struct phylink *pl,
 		 * 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;
-		else
-			neg_mode = PHYLINK_PCS_NEG_INBAND_ENABLED;
+		type = INBAND_CISCO_SGMII;
 		break;
 
 	case PHY_INTERFACE_MODE_1000BASEX:
@@ -1216,20 +1211,92 @@ static unsigned int phylink_pcs_neg_mode(struct phylink *pl,
 		 * 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;
+		type = INBAND_8023Z;
 		break;
 
 	default:
-		neg_mode = PHYLINK_PCS_NEG_NONE;
-		break;
+		return PHYLINK_PCS_NEG_NONE;
 	}
 
+	pcs_link_mode = phylink_pcs_query_inband(pcs, interface);
+	if (pl->phydev)
+		phy_link_mode = phy_query_inband(pl->phydev, interface);
+
+	if (!phylink_autoneg_inband(mode)) {
+		/* If either the PCS or PHY requires inband to be enabled,
+		 * this is an invalid configuration. Provide a diagnostic
+		 * message for this case, but don't try to force the issue.
+		 */
+		if ((pcs_link_mode | phy_link_mode) & LINK_INBAND_REQUIRED) {
+			const char *s1, *s2, *s3, *empty = "";
+
+			s1 = s2 = s3 = empty;
+			if (pcs_link_mode & LINK_INBAND_REQUIRED)
+				s1 = "PCS";
+
+			if (phy_link_mode & LINK_INBAND_REQUIRED)
+				s3 = "PHY";
+
+			if (s1 != empty && s3 != empty)
+				s2 = " and ";
+
+			phylink_warn(pl,
+				     "firmware wants %s mode, but %s%s%s requires inband\n",
+				     phylink_an_mode_str(mode),
+				     s1, s2, s3);
+		}
+		return PHYLINK_PCS_NEG_OUTBAND;
+	}
+
+	/* For SGMII modes, which are designed to be used with PHYs, we
+	 * try to use inband mode where-ever possible.
+	 */
+	if (type == INBAND_CISCO_SGMII) {
+		/* If the PCS or PHY can not provide inband, then use
+		 * out of band.
+		 */
+		if (pcs_link_mode == LINK_INBAND_VALID ||
+		    phy_link_mode == LINK_INBAND_VALID) {
+			/* If either require inband, then we have a conflict. */
+			return PHYLINK_PCS_NEG_OUTBAND;
+		}
+
+		/* Otherwise, use inband as this is what was requested.
+		 * This covers the case where the supported inband modes
+		 * have not been provided, or the PCS and PHY report that
+		 * they support inband.
+		 */
+		return PHYLINK_PCS_NEG_INBAND_ENABLED;
+	}
+
+	/* For 802.3z, handle the PHY present vs absent cases separately */
+	if (!pl->phydev) {
+		/* PHY absent: always use inband but inband may be disabled */
+		/* If the PCS doesn't support inband, then inband must be
+		 * disabled.
+		 */
+		if (pcs_link_mode == LINK_INBAND_VALID)
+			return PHYLINK_PCS_NEG_INBAND_DISABLED;
+
+		/* If the PCS requires inband, then inband must always be
+		 * enabled.
+		 */
+		if (pcs_link_mode & LINK_INBAND_REQUIRED)
+			return PHYLINK_PCS_NEG_INBAND_ENABLED;
+
+		/* For the possible case, fall through to the "legacy" code. */
+	} else {
+		/* PHY present, inband mode depends on the capabilities
+		 * of both.
+		 */
+	}
+
+	/* Legacy, so determine inband depending on the advertising bit */
+	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;
+
 	return neg_mode;
 }
 
-- 
cgit