[PATCH net-next v3] net: phy: dp83822: Fix RGMII TX delay configuration

[Tim Pambor <tp@osasysteme.de>]

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@osasysteme.de>
---
Changes in v3:
  - Revert changes involving DP83822_RGMII_MODE_EN
  - Rebase on net-next
Changes in v2:
  - Further cleanup of RGMII configuration
  - Check for errors setting DP83822_RGMII_MODE_EN
---
 drivers/net/phy/dp83822.c | 37 ++++++++++++++++++++-----------------
 1 file changed, 20 insertions(+), 17 deletions(-)

diff --git a/drivers/net/phy/dp83822.c b/drivers/net/phy/dp83822.c
index 95178e26a060..c3426a17e6d0 100644
--- a/drivers/net/phy/dp83822.c
+++ b/drivers/net/phy/dp83822.c
@@ -402,7 +402,7 @@ static int dp83822_config_init(struct phy_device *phydev)
 {
 	struct dp83822_private *dp83822 = phydev->priv;
 	struct device *dev = &phydev->mdio.dev;
-	int rgmii_delay;
+	int rgmii_delay = 0;
 	s32 rx_int_delay;
 	s32 tx_int_delay;
 	int err = 0;
@@ -412,30 +412,33 @@ static int dp83822_config_init(struct phy_device *phydev)
 		rx_int_delay = phy_get_internal_delay(phydev, dev, NULL, 0,
 						      true);
 
-		if (rx_int_delay <= 0)
-			rgmii_delay = 0;
-		else
-			rgmii_delay = DP83822_RX_CLK_SHIFT;
+		/* Set DP83822_RX_CLK_SHIFT to enable rx clk internal delay */
+		if (rx_int_delay > 0)
+			rgmii_delay |= DP83822_RX_CLK_SHIFT;
 
 		tx_int_delay = phy_get_internal_delay(phydev, dev, NULL, 0,
 						      false);
+
+		/* Set DP83822_TX_CLK_SHIFT to disable tx clk internal delay */
 		if (tx_int_delay <= 0)
-			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)
+			return err;
+
+		err = phy_set_bits_mmd(phydev, DP83822_DEVADDR,
+				       MII_DP83822_RCSR, DP83822_RGMII_MODE_EN);
 
-		phy_set_bits_mmd(phydev, DP83822_DEVADDR,
-					MII_DP83822_RCSR, DP83822_RGMII_MODE_EN);
+		if (err)
+			return err;
 	} else {
-		phy_clear_bits_mmd(phydev, DP83822_DEVADDR,
-					MII_DP83822_RCSR, DP83822_RGMII_MODE_EN);
+		err = phy_clear_bits_mmd(phydev, DP83822_DEVADDR,
+					 MII_DP83822_RCSR, DP83822_RGMII_MODE_EN);
+
+		if (err)
+			return err;
 	}
 
 	if (dp83822->fx_enabled) {
-- 
2.43.0