[RFC PATCH 06/10] net: pcs: xpcs: improve SGMII AN state handling for Rockchip RK3568

[Coia Prant <coiaprant@gmail.com>]

Commit 2a22b7ae2fa3 ("net: pcs: xpcs: adapt Wangxun NICs for SGMII mode")
added support for reading CL37_ANCMPLT_INTR and then reading BMCR for
speed/duplex.  This may work on Wangxun hardware but not on RK3568.

On RK3568, reading BMCR returns a fixed value (HW Reset Value or Write
Manual) instead of the negotiated result, so the correct speed/duplex
must be read from CL37_ANSGM_STS.  Also, when the link is down,
CL37_ANCMPLT_INTR stays set and the PCS does not restart AN automatically
when the PHY link returns, so an explicit AN restart via BMCR_ANRESTART
is needed.

Modify xpcs_get_state_c37_sgmii() to check CL37_ANSGM_STS for link
status first.  If the link is up, report the state.  If AN is complete
(CL37_ANCMPLT_INTR set), clear the interrupt and restart AN for
non-Wangxun platforms.  The original Wangxun-specific path is kept
unchanged unless we confirm it's a bug not a feature.

Also clear CL37 AN complete status in xpcs_config_aneg_c37_sgmii()
before starting AN to ensure a clean initial state.

Fixes: 2a22b7ae2fa3 ("net: pcs: xpcs: adapt Wangxun NICs for SGMII mode")
Signed-off-by: Coia Prant <coiaprant@gmail.com>
---
 drivers/net/pcs/pcs-xpcs.c | 31 ++++++++++++++++++++++++++++---
 1 file changed, 28 insertions(+), 3 deletions(-)

diff --git a/drivers/net/pcs/pcs-xpcs.c b/drivers/net/pcs/pcs-xpcs.c
index e69fa2f0a0e8d..cf370ba247cac 100644
--- a/drivers/net/pcs/pcs-xpcs.c
+++ b/drivers/net/pcs/pcs-xpcs.c
@@ -816,6 +816,11 @@ static int xpcs_config_aneg_c37_sgmii(struct dw_xpcs *xpcs,
 	if (ret < 0)
 		return ret;
 
+	/* Clear CL37 AN complete status */
+	ret = xpcs_write(xpcs, MDIO_MMD_VEND2, DW_VR_MII_AN_INTR_STS, 0);
+	if (ret < 0)
+		return ret;
+
 	if (neg_mode == PHYLINK_PCS_NEG_INBAND_ENABLED)
 		ret = xpcs_write(xpcs, MDIO_MMD_VEND2, MII_BMCR,
 				 mdio_ctrl | BMCR_ANENABLE);
@@ -884,7 +889,7 @@ static int xpcs_config_aneg_c37_1000basex(struct dw_xpcs *xpcs,
 
 	if (neg_mode == PHYLINK_PCS_NEG_INBAND_ENABLED) {
 		ret = xpcs_write(xpcs, MDIO_MMD_VEND2, MII_BMCR,
-				 mdio_ctrl | BMCR_ANENABLE);
+				 mdio_ctrl | BMCR_ANENABLE | BMCR_ANRESTART);
 		if (ret < 0)
 			return ret;
 	}
@@ -1058,6 +1063,7 @@ static int xpcs_get_state_c37_sgmii(struct dw_xpcs *xpcs,
 
 	/* Reset link_state */
 	state->link = false;
+	state->an_complete = false;
 	state->speed = SPEED_UNKNOWN;
 	state->duplex = DUPLEX_UNKNOWN;
 	state->pause = 0;
@@ -1069,6 +1075,8 @@ static int xpcs_get_state_c37_sgmii(struct dw_xpcs *xpcs,
 	if (ret < 0)
 		return ret;
 
+	state->an_complete = ret & DW_VR_MII_AN_STS_C37_ANCMPLT_INTR;
+
 	if (ret & DW_VR_MII_C37_ANSGM_SP_LNKSTS) {
 		int speed_value;
 
@@ -1086,7 +1094,24 @@ static int xpcs_get_state_c37_sgmii(struct dw_xpcs *xpcs,
 			state->duplex = DUPLEX_FULL;
 		else
 			state->duplex = DUPLEX_HALF;
-	} else if (ret == DW_VR_MII_AN_STS_C37_ANCMPLT_INTR) {
+
+		return 0;
+	}
+
+	/* Clear AN complete status or interrupt */
+	if (state->an_complete)
+		xpcs_write(xpcs, MDIO_MMD_VEND2, DW_VR_MII_AN_INTR_STS, 0);
+
+	if (xpcs->info.pma != WX_TXGBE_XPCS_PMA_10G_ID) {
+		/* If the link down, restart Auto-Negotiation */
+		if (state->an_complete)
+			xpcs_modify(xpcs, MDIO_MMD_VEND2, MII_BMCR, BMCR_ANRESTART,
+				    BMCR_ANRESTART);
+
+		return 0;
+	}
+
+	if (ret == DW_VR_MII_AN_STS_C37_ANCMPLT_INTR) {
 		int speed, duplex;
 
 		state->link = true;
@@ -1112,7 +1137,7 @@ static int xpcs_get_state_c37_sgmii(struct dw_xpcs *xpcs,
 		else if (duplex & ADVERTISE_1000XHALF)
 			state->duplex = DUPLEX_HALF;
 
-		xpcs_write(xpcs, MDIO_MMD_VEND2, DW_VR_MII_AN_INTR_STS, 0);
+		return 0;
 	}
 
 	return 0;
-- 
2.47.3