Merge branch 'net-phylink-fix-pcs-without-autoneg'

Russell King says:

====================
net: phylink: fix PCS without autoneg

Eric Woudstra reported that a PCS attached using 2500base-X does not
see link when phylink is using in-band mode, but autoneg is disabled,
despite there being a valid 2500base-X signal being received. We have
these settings:

	act_link_an_mode = MLO_AN_INBAND
	pcs_neg_mode = PHYLINK_PCS_NEG_INBAND_DISABLED

Eric diagnosed it to phylink_decode_c37_word() setting state->link
false because the full-duplex bit isn't set in the non-existent link
partner advertisement word (which doesn't exist because in-band
autoneg is disabled!)

The test in phylink_mii_c22_pcs_decode_state() is supposed to catch
this state, but since we converted PCS to use neg_mode, testing the
Autoneg in the local advertisement is no longer sufficient - we need
to be looking at the neg_mode, which currently isn't provided.

We need to provide this via the .pcs_get_state() method, and this
will require modifying all PCS implementations to add the extra
argument to this method.

Patch 1 uses the PCS neg_mode in phylink_mac_pcs_get_state() to correct
the now obsolute usage of the Autoneg bit in the advertisement.

Patch 2 passes neg_mode into the .pcs_get_state() method, and updates
all users.

Patch 3 adds neg_mode as an argument to the various clause 22 state
decoder functions in phylink, modifying drivers to pass the neg_mode
through.

Patch 4 makes use of phylink_mii_c22_pcs_decode_state() rather than
using the Autoneg bit in the advertising field.

Patch 5 may be required for Eric's case - it ensures that we report
the correct state for interface types that we support only one set
of modes for when autoneg is disabled.
====================

Link: https://patch.msgid.link/Z4TbR93B-X8A8iHe@shell.armlinux.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 43 insertions, 17 deletions

diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
index 31754d5fd659..ff0efb52189f 100644
--- a/drivers/net/phy/phylink.c
+++ b/drivers/net/phy/phylink.c
@@ -1492,12 +1492,24 @@ static int phylink_change_inband_advert(struct phylink *pl)
 static void phylink_mac_pcs_get_state(struct phylink *pl,
 				      struct phylink_link_state *state)
 {
+	struct phylink_pcs *pcs;
+	bool autoneg;
+
 	linkmode_copy(state->advertising, pl->link_config.advertising);
 	linkmode_zero(state->lp_advertising);
 	state->interface = pl->link_config.interface;
 	state->rate_matching = pl->link_config.rate_matching;
-	if (linkmode_test_bit(ETHTOOL_LINK_MODE_Autoneg_BIT,
-			      state->advertising)) {
+	state->an_complete = 0;
+	state->link = 1;
+
+	pcs = pl->pcs;
+	if (!pcs || pcs->neg_mode)
+		autoneg = pl->pcs_neg_mode == PHYLINK_PCS_NEG_INBAND_ENABLED;
+	else
+		autoneg = linkmode_test_bit(ETHTOOL_LINK_MODE_Autoneg_BIT,
+					    state->advertising);
+
+	if (autoneg) {
 		state->speed = SPEED_UNKNOWN;
 		state->duplex = DUPLEX_UNKNOWN;
 		state->pause = MLO_PAUSE_NONE;
@@ -1506,11 +1518,9 @@ static void phylink_mac_pcs_get_state(struct phylink *pl,
 		state->duplex = pl->link_config.duplex;
 		state->pause = pl->link_config.pause;
 	}
-	state->an_complete = 0;
-	state->link = 1;
 
-	if (pl->pcs)
-		pl->pcs->ops->pcs_get_state(pl->pcs, state);
+	if (pcs)
+		pcs->ops->pcs_get_state(pcs, pl->pcs_neg_mode, state);
 	else
 		state->link = 0;
 }
@@ -3850,6 +3860,7 @@ static void phylink_decode_usgmii_word(struct phylink_link_state *state,
 /**
  * phylink_mii_c22_pcs_decode_state() - Decode MAC PCS state from MII registers
  * @state: a pointer to a &struct phylink_link_state.
+ * @neg_mode: link negotiation mode (PHYLINK_PCS_NEG_xxx)
  * @bmsr: The value of the %MII_BMSR register
  * @lpa: The value of the %MII_LPA register
  *
@@ -3862,32 +3873,45 @@ static void phylink_decode_usgmii_word(struct phylink_link_state *state,
  * accessing @bmsr and @lpa cannot be done with MDIO directly.
  */
 void phylink_mii_c22_pcs_decode_state(struct phylink_link_state *state,
-				      u16 bmsr, u16 lpa)
+				      unsigned int neg_mode, u16 bmsr, u16 lpa)
 {
 	state->link = !!(bmsr & BMSR_LSTATUS);
 	state->an_complete = !!(bmsr & BMSR_ANEGCOMPLETE);
-	/* 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 || !linkmode_test_bit(ETHTOOL_LINK_MODE_Autoneg_BIT,
-					       state->advertising))
+
+	/* If the link is down, the advertisement data is undefined. */
+	if (!state->link)
 		return;
 
 	switch (state->interface) {
 	case PHY_INTERFACE_MODE_1000BASEX:
-		phylink_decode_c37_word(state, lpa, SPEED_1000);
+		if (neg_mode == PHYLINK_PCS_NEG_INBAND_ENABLED) {
+			phylink_decode_c37_word(state, lpa, SPEED_1000);
+		} else {
+			state->speed = SPEED_1000;
+			state->duplex = DUPLEX_FULL;
+			state->pause |= MLO_PAUSE_TX | MLO_PAUSE_RX;
+		}
 		break;
 
 	case PHY_INTERFACE_MODE_2500BASEX:
-		phylink_decode_c37_word(state, lpa, SPEED_2500);
+		if (neg_mode == PHYLINK_PCS_NEG_INBAND_ENABLED) {
+			phylink_decode_c37_word(state, lpa, SPEED_2500);
+		} else {
+			state->speed = SPEED_2500;
+			state->duplex = DUPLEX_FULL;
+			state->pause |= MLO_PAUSE_TX | MLO_PAUSE_RX;
+		}
 		break;
 
 	case PHY_INTERFACE_MODE_SGMII:
 	case PHY_INTERFACE_MODE_QSGMII:
-		phylink_decode_sgmii_word(state, lpa);
+		if (neg_mode == PHYLINK_PCS_NEG_INBAND_ENABLED)
+			phylink_decode_sgmii_word(state, lpa);
 		break;
+
 	case PHY_INTERFACE_MODE_QUSGMII:
-		phylink_decode_usgmii_word(state, lpa);
+		if (neg_mode == PHYLINK_PCS_NEG_INBAND_ENABLED)
+			phylink_decode_usgmii_word(state, lpa);
 		break;
 
 	default:
@@ -3900,6 +3924,7 @@ EXPORT_SYMBOL_GPL(phylink_mii_c22_pcs_decode_state);
 /**
  * phylink_mii_c22_pcs_get_state() - read the MAC PCS state
  * @pcs: a pointer to a &struct mdio_device.
+ * @neg_mode: link negotiation mode (PHYLINK_PCS_NEG_xxx)
  * @state: a pointer to a &struct phylink_link_state.
  *
  * Helper for MAC PCS supporting the 802.3 clause 22 register set for
@@ -3912,6 +3937,7 @@ EXPORT_SYMBOL_GPL(phylink_mii_c22_pcs_decode_state);
  * structure.
  */
 void phylink_mii_c22_pcs_get_state(struct mdio_device *pcs,
+				   unsigned int neg_mode,
 				   struct phylink_link_state *state)
 {
 	int bmsr, lpa;
@@ -3923,7 +3949,7 @@ void phylink_mii_c22_pcs_get_state(struct mdio_device *pcs,
 		return;
 	}
 
-	phylink_mii_c22_pcs_decode_state(state, bmsr, lpa);
+	phylink_mii_c22_pcs_decode_state(state, neg_mode, bmsr, lpa);
 }
 EXPORT_SYMBOL_GPL(phylink_mii_c22_pcs_get_state);