netdev - [PATCH net-next 2/3] net: phy: dp83869: ensure FORCE_LINK

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Message-Id: <20250514-dp83869-1000basex-v1-2-1bdb3c9c3d63@bootlin.com>
Date: Wed, 14 May 2025 09:49:58 +0200
From: Romain Gantois <romain.gantois@...tlin.com>
To: Andrew Lunn <andrew@...n.ch>, Heiner Kallweit <hkallweit1@...il.com>, 
 Russell King <linux@...linux.org.uk>, 
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Cc: Maxime Chevallier <maxime.chevallier@...tlin.com>, 
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>, netdev@...r.kernel.org, 
 linux-kernel@...r.kernel.org, Romain Gantois <romain.gantois@...tlin.com>
Subject: [PATCH net-next 2/3] net: phy: dp83869: ensure FORCE_LINK_GOOD is
 cleared

The FORCE_LINK_GOOD bit in the PHY_CONTROL register forces the reported
link status to 1 if the selected speed is 1Gbps.

According to the DP83869 PHY datasheet, this bit should default to 0 after
a hardware reset. However, the opposite has been observed on some DP83869
components.

As a consequence, a valid link will be reported in 1000Base-X operational
modes, even if the autonegotiation process failed.

Make sure that the FORCE_LINK_GOOD bit is cleared during initial
configuration.

Signed-off-by: Romain Gantois <romain.gantois@...tlin.com>
---
 drivers/net/phy/dp83869.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/net/phy/dp83869.c b/drivers/net/phy/dp83869.c
index 010434c94e01f44ac3c0b7e147468f4f7dca33f4..000660aae16ed46166774e7235cd8a6df94be047 100644
--- a/drivers/net/phy/dp83869.c
+++ b/drivers/net/phy/dp83869.c
@@ -89,6 +89,7 @@
 #define DP83869_STRAP_MIRROR_ENABLED           BIT(12)

 /* PHYCTRL bits */
+#define DP83869_FORCE_LINK_GOOD	BIT(10)
 #define DP83869_RX_FIFO_SHIFT	12
 #define DP83869_TX_FIFO_SHIFT	14

@@ -810,6 +811,15 @@ static int dp83869_config_init(struct phy_device *phydev)
 	struct dp83869_private *dp83869 = phydev->priv;
 	int ret, val;

+	/* The FORCE_LINK_GOOD bit in the PHYCTRL register should be
+	 * unset after a hardware reset but it is not. make sure it is
+	 * cleared so that the PHY can function properly.
+	 */
+	ret = phy_clear_bits(phydev, MII_DP83869_PHYCTRL,
+			     DP83869_FORCE_LINK_GOOD);
+	if (ret)
+		return ret;
+
 	/* Force speed optimization for the PHY even if it strapped */
 	ret = phy_modify(phydev, DP83869_CFG2, DP83869_DOWNSHIFT_EN,
 			 DP83869_DOWNSHIFT_EN);

-- 
2.49.0