net: phy: micrel: Add loopback support

The KSZ9031 PHYs requires full duplex for loopback mode. Add PHY
specific set_loopback() to ensure this.

Signed-off-by: Gerhard Engleder <gerhard@engleder-embedded.com>
Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Link: https://patch.msgid.link/20250312203010.47429-4-gerhard@engleder-embedded.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/drivers/net/phy/micrel.c b/drivers/net/phy/micrel.c
index 289e1d56aa655998fbbc4d955f783be132b1af12..24882d30f68589b2b821d13decdb9f858cdaa609 100644 (file)
--- a/drivers/net/phy/micrel.c
+++ b/drivers/net/phy/micrel.c
@@ -1032,6 +1032,29 @@ static int ksz9021_config_init(struct phy_device *phydev)
 #define MII_KSZ9031RN_EDPD             0x23
 #define MII_KSZ9031RN_EDPD_ENABLE      BIT(0)
 
+static int ksz9031_set_loopback(struct phy_device *phydev, bool enable,
+                               int speed)
+{
+       u16 ctl = BMCR_LOOPBACK;
+       int val;
+
+       if (!enable)
+               return genphy_loopback(phydev, enable, 0);
+
+       if (speed == SPEED_10 || speed == SPEED_100 || speed == SPEED_1000)
+               phydev->speed = speed;
+       else if (speed)
+               return -EINVAL;
+       phydev->duplex = DUPLEX_FULL;
+
+       ctl |= mii_bmcr_encode_fixed(phydev->speed, phydev->duplex);
+
+       phy_write(phydev, MII_BMCR, ctl);
+
+       return phy_read_poll_timeout(phydev, MII_BMSR, val, val & BMSR_LSTATUS,
+                                    5000, 500000, true);
+}
+
 static int ksz9031_of_load_skew_values(struct phy_device *phydev,
                                       const struct device_node *of_node,
                                       u16 reg, size_t field_sz,
@@ -5565,6 +5588,7 @@ static struct phy_driver ksphy_driver[] = {
        .resume         = kszphy_resume,
        .cable_test_start       = ksz9x31_cable_test_start,
        .cable_test_get_status  = ksz9x31_cable_test_get_status,
+       .set_loopback   = ksz9031_set_loopback,
 }, {
        .phy_id         = PHY_ID_LAN8814,
        .phy_id_mask    = MICREL_PHY_ID_MASK,