From 880d1311335120f64447ca9d11933872d734e19a Mon Sep 17 00:00:00 2001
From: Daniel Golle <daniel@makrotopia.org>
Date: Mon, 27 Mar 2023 18:41:54 +0100
Subject: [PATCH] generic: pcs-mtk-lynxi: add hack to use 2500Base-X without AN

Using 2500Base-T SFP modules e.g. on the BananaPi R3 requires manually
disabling auto-negotiation, e.g. using ethtool. While a proper fix
using SFP quirks is being discussed upstream, bring a work-around to
restore user experience to what it was before the switch to the
dedicated SGMII PCS driver.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>

--- a/drivers/net/pcs/pcs-mtk-lynxi.c
+++ b/drivers/net/pcs/pcs-mtk-lynxi.c
@@ -114,14 +114,23 @@ static void mtk_pcs_lynxi_get_state(stru
 				    struct phylink_link_state *state)
 {
 	struct mtk_pcs_lynxi *mpcs = pcs_to_mtk_pcs_lynxi(pcs);
-	unsigned int bm, adv;
+	unsigned int bm, bmsr, adv;
 
 	/* Read the BMSR and LPA */
 	regmap_read(mpcs->regmap, SGMSYS_PCS_CONTROL_1, &bm);
-	regmap_read(mpcs->regmap, SGMSYS_PCS_ADVERTISE, &adv);
+	bmsr = FIELD_GET(SGMII_BMSR, bm);
+
+	if (state->interface == PHY_INTERFACE_MODE_2500BASEX) {
+		state->link = !!(bmsr & BMSR_LSTATUS);
+		state->an_complete = !!(bmsr & BMSR_ANEGCOMPLETE);
+		state->speed = SPEED_2500;
+		state->duplex = DUPLEX_FULL;
+
+		return;
+	}
 
-	phylink_mii_c22_pcs_decode_state(state, FIELD_GET(SGMII_BMSR, bm),
-					 FIELD_GET(SGMII_LPA, adv));
+	regmap_read(mpcs->regmap, SGMSYS_PCS_ADVERTISE, &adv);
+	phylink_mii_c22_pcs_decode_state(state, bmsr, FIELD_GET(SGMII_LPA, adv));
 }
 
 static void mtk_sgmii_reset(struct mtk_pcs_lynxi *mpcs)
@@ -142,7 +151,7 @@ static int mtk_pcs_lynxi_config(struct p
 {
 	struct mtk_pcs_lynxi *mpcs = pcs_to_mtk_pcs_lynxi(pcs);
 	bool mode_changed = false, changed;
-	unsigned int rgc3, sgm_mode, bmcr;
+	unsigned int rgc3, sgm_mode, bmcr = 0;
 	int advertise, link_timer;
 
 	advertise = phylink_mii_c22_pcs_encode_advertisement(interface,
@@ -165,9 +174,8 @@ static int mtk_pcs_lynxi_config(struct p
 	if (neg_mode == PHYLINK_PCS_NEG_INBAND_ENABLED) {
 		if (interface == PHY_INTERFACE_MODE_SGMII)
 			sgm_mode |= SGMII_SPEED_DUPLEX_AN;
-		bmcr = BMCR_ANENABLE;
-	} else {
-		bmcr = 0;
+		if (interface != PHY_INTERFACE_MODE_2500BASEX)
+			bmcr = BMCR_ANENABLE;
 	}
 
 	if (mpcs->interface != interface) {