FAILED: patch "[PATCH] net: pcs: xpcs: fix SGMII state reading" failed to apply to 6.12-stable tree

The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x def9a4745e105145133e442dd8a1c126caf0f553
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026072904-shallow-icing-2a9f@gregkh' --subject-prefix 'PATCH 6.12.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From def9a4745e105145133e442dd8a1c126caf0f553 Mon Sep 17 00:00:00 2001
From: Coia Prant <[email protected]>
Date: Fri, 17 Jul 2026 15:43:25 +0800
Subject: [PATCH] net: pcs: xpcs: fix SGMII state reading

Commit 2a22b7ae2fa3 ("net: pcs: xpcs: adapt Wangxun NICs for SGMII mode") added a path in xpcs_get_state_c37_sgmii() that reads speed/duplex from BMCR after AN completes. However, BMCR does not reflect the negotiated result on the hardware where this has been tested:

- On RK3568 (MAC side SGMII), BMCR returns a fixed hardware reset value
- Wangxun engineer Jiawen Wu confirmed that on their side, "BMCR looks like it only wants to be return as 0" [0]

The correct information is available in CL37_ANSGM_STS, which contains the actual link status and negotiated speed/duplex.

This bug was previously masked by phylink core, which overrides the PCS link state with the PHY state when a PHY is present:

        /* If we have a phy, the "up" state is the union of both the
         * PHY and the MAC
         */
        if (phy)
                link_state.link &= pl->phy_state.link;

Thus, when the link is down, the PHY's link_down state is applied on top of whatever the PCS reports, hiding the broken PCS state reading path.

Modify xpcs_get_state_c37_sgmii() to:
1. Read link state from CL37_ANSGM_STS
2. If link is up, report speed/duplex from CL37_ANSGM_STS
3. Remove the broken BMCR reading path entirely

Also properly set state->an_complete to reflect the AN completion status, and clear CL37_ANCMPLT_INTR when link is down to avoid stale state.

[0] https://lore.kernel.org/all/[email protected]/

index e69fa2f0a0e8..0337e2bcc012 100644
@@ -1058,6 +1058,7 @@ 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 +1070,8 @@ 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;
 

@@ -1086,35 +1089,14 @@ 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) {
-		int speed, duplex;
 
-		state->link = true;
-
-		speed = xpcs_read(xpcs, MDIO_MMD_VEND2, MII_BMCR);
-		if (speed < 0)
-			return speed;
-
-		speed &= BMCR_SPEED100 | BMCR_SPEED1000;
-		if (speed == BMCR_SPEED1000)
-			state->speed = SPEED_1000;
-		else if (speed == BMCR_SPEED100)
-			state->speed = SPEED_100;
-		else if (speed == 0)
-			state->speed = SPEED_10;
-
-		duplex = xpcs_read(xpcs, MDIO_MMD_VEND2, MII_ADVERTISE);
-		if (duplex < 0)
-			return duplex;
-
-		if (duplex & ADVERTISE_1000XFULL)
-			state->duplex = DUPLEX_FULL;
-		else if (duplex & ADVERTISE_1000XHALF)
-			state->duplex = DUPLEX_HALF;
-
-		xpcs_write(xpcs, MDIO_MMD_VEND2, DW_VR_MII_AN_INTR_STS, 0);
+		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);
+
 	return 0;
 }
 

Commit 2a22b7ae2fa3 ("net: pcs: xpcs: adapt Wangxun NICs for SGMII mode") added a path in xpcs_get_state_c37_sgmii() that reads speed/duplex from BMCR after AN completes. However, BMCR does not reflect the negotiated result on the hardware where this has been tested:

- On RK3568 (MAC side SGMII), BMCR returns a fixed hardware reset value
- Wangxun engineer Jiawen Wu confirmed that on their side, "BMCR looks like it only wants to be return as 0" [0]

The correct information is available in CL37_ANSGM_STS, which contains the actual link status and negotiated speed/duplex.

This bug was previously masked by phylink core, which overrides the PCS link state with the PHY state when a PHY is present:

        /* If we have a phy, the "up" state is the union of both the
         * PHY and the MAC
         */
        if (phy)
                link_state.link &= pl->phy_state.link;

Thus, when the link is down, the PHY's link_down state is applied on top of whatever the PCS reports, hiding the broken PCS state reading path.

Modify xpcs_get_state_c37_sgmii() to:
1. Read link state from CL37_ANSGM_STS
2. If link is up, report speed/duplex from CL37_ANSGM_STS
3. Remove the broken BMCR reading path entirely

Also properly set state->an_complete to reflect the AN completion status, and clear CL37_ANCMPLT_INTR when link is down to avoid stale state.

[0] https://lore.kernel.org/all/[email protected]/

---
 drivers/net/pcs/pcs-xpcs.c | 32 +++++++-------------------------
 1 file changed, 7 insertions(+), 25 deletions(-)

index 82463f9d50c8..0152f820c1bb 100644
@@ -973,6 +973,7 @@ 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;

@@ -984,6 +985,8 @@ 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;
 

@@ -1002,34 +1005,13 @@ 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) {
-		int speed, duplex;
-
-		state->link = true;
-
-		speed = xpcs_read(xpcs, MDIO_MMD_VEND2, MDIO_CTRL1);
-		if (speed < 0)
-			return speed;
-
-		speed &= SGMII_SPEED_SS13 | SGMII_SPEED_SS6;
-		if (speed == SGMII_SPEED_SS6)
-			state->speed = SPEED_1000;
-		else if (speed == SGMII_SPEED_SS13)
-			state->speed = SPEED_100;
-		else if (speed == 0)
-			state->speed = SPEED_10;
-
-		duplex = xpcs_read(xpcs, MDIO_MMD_VEND2, MII_ADVERTISE);
-		if (duplex < 0)
-			return duplex;
 
-		if (duplex & DW_FULL_DUPLEX)
-			state->duplex = DUPLEX_FULL;
-		else if (duplex & DW_HALF_DUPLEX)
-			state->duplex = DUPLEX_HALF;
+		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);
-	}
 
 	return 0;
 }

2.47.3

Queued for 6.12 and 6.6, thanks.

Thanks,
Sasha