net: phy: dp83822: Add support for changing the transmit amplitude voltage

Add support for changing the transmit amplitude voltage in 100BASE-TX mode.
Modifying it can be necessary to compensate losses on the PCB and
connector, so the voltages measured on the RJ45 pins are conforming.

Signed-off-by: Dimitri Fedrau <dimitri.fedrau@liebherr.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20250214-dp83822-tx-swing-v5-3-02ca72620599@liebherr.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/phy/dp83822.c b/drivers/net/phy/dp83822.c
index 6599feca1967d705331d6e354205a2485ea962f2..3662f3905d5ade8ad933608fcaeabb714a588418 100644 (file)
--- a/drivers/net/phy/dp83822.c
+++ b/drivers/net/phy/dp83822.c
@@ -31,6 +31,7 @@
 #define MII_DP83822_RCSR       0x17
 #define MII_DP83822_RESET_CTRL 0x1f
 #define MII_DP83822_MLEDCR     0x25
+#define MII_DP83822_LDCTRL     0x403
 #define MII_DP83822_LEDCFG1    0x460
 #define MII_DP83822_IOCTRL1    0x462
 #define MII_DP83822_IOCTRL2    0x463
@@ -123,6 +124,9 @@
 #define DP83822_IOCTRL1_GPIO1_CTRL             GENMASK(2, 0)
 #define DP83822_IOCTRL1_GPIO1_CTRL_LED_1       BIT(0)
 
+/* LDCTRL bits */
+#define DP83822_100BASE_TX_LINE_DRIVER_SWING   GENMASK(7, 4)
+
 /* IOCTRL2 bits */
 #define DP83822_IOCTRL2_GPIO2_CLK_SRC          GENMASK(6, 4)
 #define DP83822_IOCTRL2_GPIO2_CTRL             GENMASK(2, 0)
@@ -197,6 +201,7 @@ struct dp83822_private {
        bool set_gpio2_clk_out;
        u32 gpio2_clk_out;
        bool led_pin_enable[DP83822_MAX_LED_PINS];
+       int tx_amplitude_100base_tx_index;
 };
 
 static int dp83822_config_wol(struct phy_device *phydev,
@@ -522,6 +527,12 @@ static int dp83822_config_init(struct phy_device *phydev)
                               FIELD_PREP(DP83822_IOCTRL2_GPIO2_CLK_SRC,
                                          dp83822->gpio2_clk_out));
 
+       if (dp83822->tx_amplitude_100base_tx_index >= 0)
+               phy_modify_mmd(phydev, MDIO_MMD_VEND2, MII_DP83822_LDCTRL,
+                              DP83822_100BASE_TX_LINE_DRIVER_SWING,
+                              FIELD_PREP(DP83822_100BASE_TX_LINE_DRIVER_SWING,
+                                         dp83822->tx_amplitude_100base_tx_index));
+
        err = dp83822_config_init_leds(phydev);
        if (err)
                return err;
@@ -720,6 +731,11 @@ static int dp83822_phy_reset(struct phy_device *phydev)
 }
 
 #ifdef CONFIG_OF_MDIO
+static const u32 tx_amplitude_100base_tx_gain[] = {
+       80, 82, 83, 85, 87, 88, 90, 92,
+       93, 95, 97, 98, 100, 102, 103, 105,
+};
+
 static int dp83822_of_init_leds(struct phy_device *phydev)
 {
        struct device_node *node = phydev->mdio.dev.of_node;
@@ -780,6 +796,8 @@ static int dp83822_of_init(struct phy_device *phydev)
        struct dp83822_private *dp83822 = phydev->priv;
        struct device *dev = &phydev->mdio.dev;
        const char *of_val;
+       int i, ret;
+       u32 val;
 
        /* Signal detection for the PHY is only enabled if the FX_EN and the
         * SD_EN pins are strapped. Signal detection can only enabled if FX_EN
@@ -815,6 +833,26 @@ static int dp83822_of_init(struct phy_device *phydev)
                dp83822->set_gpio2_clk_out = true;
        }
 
+       dp83822->tx_amplitude_100base_tx_index = -1;
+       ret = phy_get_tx_amplitude_gain(phydev, dev,
+                                       ETHTOOL_LINK_MODE_100baseT_Full_BIT,
+                                       &val);
+       if (!ret) {
+               for (i = 0; i < ARRAY_SIZE(tx_amplitude_100base_tx_gain); i++) {
+                       if (tx_amplitude_100base_tx_gain[i] == val) {
+                               dp83822->tx_amplitude_100base_tx_index = i;
+                               break;
+                       }
+               }
+
+               if (dp83822->tx_amplitude_100base_tx_index < 0) {
+                       phydev_err(phydev,
+                                  "Invalid value for tx-amplitude-100base-tx-percent property (%u)\n",
+                                  val);
+                       return -EINVAL;
+               }
+       }
+
        return dp83822_of_init_leds(phydev);
 }