linux-kernel - [PATCH] net: phy: dp83822: Fix RGMII TX delay configuration

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Date: Sat,  3 Feb 2024 14:11:51 +0100
From: Tim Pambor <tp@...systeme.de>
To: Andrew Lunn <andrew@...n.ch>
Cc: 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>,
	Dan Murphy <dmurphy@...com>,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Tim Pambor <tp@...systeme.de>
Subject: [PATCH] net: phy: dp83822: Fix RGMII TX delay configuration

The logic for enabling the TX clock shift is inverse of enabling the RX
clock shift. The TX clock shift is disabled when DP83822_TX_CLK_SHIFT is
set. Correct the current behavior and always write the delay configuration
to ensure consistent delay settings regardless of bootloader configuration.

Reference: https://www.ti.com/lit/ds/symlink/dp83822i.pdf p. 69

Fixes: 8095295292b5 ("net: phy: DP83822: Add setting the fixed internal delay")
Signed-off-by: Tim Pambor <tp@...systeme.de>
---
 drivers/net/phy/dp83822.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/drivers/net/phy/dp83822.c b/drivers/net/phy/dp83822.c
index b7cb71817780..b061036f654a 100644
--- a/drivers/net/phy/dp83822.c
+++ b/drivers/net/phy/dp83822.c
@@ -398,16 +398,15 @@ static int dp83822_config_init(struct phy_device *phydev)
 		tx_int_delay = phy_get_internal_delay(phydev, dev, NULL, 0,
 						      false);
 		if (tx_int_delay <= 0)
-			rgmii_delay &= ~DP83822_TX_CLK_SHIFT;
-		else
 			rgmii_delay |= DP83822_TX_CLK_SHIFT;
+		else
+			rgmii_delay &= ~DP83822_TX_CLK_SHIFT;
 
-		if (rgmii_delay) {
-			err = phy_set_bits_mmd(phydev, DP83822_DEVADDR,
-					       MII_DP83822_RCSR, rgmii_delay);
-			if (err)
-				return err;
-		}
+		err = phy_modify_mmd(phydev, DP83822_DEVADDR, MII_DP83822_RCSR,
+				     DP83822_RX_CLK_SHIFT | DP83822_TX_CLK_SHIFT, rgmii_delay);
+
+		if (err < 0)
+			return err;
 
 		phy_set_bits_mmd(phydev, DP83822_DEVADDR,
 					MII_DP83822_RCSR, DP83822_RGMII_MODE_EN);
-- 
2.43.0