net: phy: adin: allow control of Fast Link Down

Add support to allow Fast Link Down (aka "Enhanced link detection") to
be controlled via the ETHTOOL_PHY_FAST_LINK_DOWN tunable. These PHYs
have this feature enabled by default.

Signed-off-by: Vincent Whitchurch <[e-mail]>
Acked-by: Nuno Sa <[e-mail]>
Reviewed-by: Andrew Lunn <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/phy/adin.c

···
 #define ADIN1300_EEE_CAP_REG			0x8000
 #define ADIN1300_EEE_ADV_REG			0x8001
 #define ADIN1300_EEE_LPABLE_REG			0x8002
+
+#define ADIN1300_FLD_EN_REG			0x8E27
+#define   ADIN1300_FLD_PCS_ERR_100_EN		BIT(7)
+#define   ADIN1300_FLD_PCS_ERR_1000_EN		BIT(6)
+#define   ADIN1300_FLD_SLCR_OUT_STUCK_100_EN	BIT(5)
+#define   ADIN1300_FLD_SLCR_OUT_STUCK_1000_EN	BIT(4)
+#define   ADIN1300_FLD_SLCR_IN_ZDET_100_EN	BIT(3)
+#define   ADIN1300_FLD_SLCR_IN_ZDET_1000_EN	BIT(2)
+#define   ADIN1300_FLD_SLCR_IN_INVLD_100_EN	BIT(1)
+#define   ADIN1300_FLD_SLCR_IN_INVLD_1000_EN	BIT(0)
+/* These bits are the ones which are enabled by default. */
+#define ADIN1300_FLD_EN_ON	\
+	(ADIN1300_FLD_SLCR_OUT_STUCK_100_EN | \
+	 ADIN1300_FLD_SLCR_OUT_STUCK_1000_EN | \
+	 ADIN1300_FLD_SLCR_IN_ZDET_100_EN | \
+	 ADIN1300_FLD_SLCR_IN_ZDET_1000_EN | \
+	 ADIN1300_FLD_SLCR_IN_INVLD_1000_EN)
+
 #define ADIN1300_CLOCK_STOP_REG			0x9400
 #define ADIN1300_LPI_WAKE_ERR_CNT_REG		0xa000
 
···
 			  val);
 }
 
+static int adin_get_fast_down(struct phy_device *phydev, u8 *msecs)
+{
+	int reg;
+
+	reg = phy_read_mmd(phydev, MDIO_MMD_VEND1, ADIN1300_FLD_EN_REG);
+	if (reg < 0)
+		return reg;
+
+	if (reg & ADIN1300_FLD_EN_ON)
+		*msecs = ETHTOOL_PHY_FAST_LINK_DOWN_ON;
+	else
+		*msecs = ETHTOOL_PHY_FAST_LINK_DOWN_OFF;
+
+	return 0;
+}
+
+static int adin_set_fast_down(struct phy_device *phydev, const u8 *msecs)
+{
+	if (*msecs == ETHTOOL_PHY_FAST_LINK_DOWN_ON)
+		return phy_set_bits_mmd(phydev, MDIO_MMD_VEND1,
+					ADIN1300_FLD_EN_REG,
+					ADIN1300_FLD_EN_ON);
+
+	if (*msecs == ETHTOOL_PHY_FAST_LINK_DOWN_OFF)
+		return phy_clear_bits_mmd(phydev, MDIO_MMD_VEND1,
+					  ADIN1300_FLD_EN_REG,
+					  ADIN1300_FLD_EN_ON);
+
+	return -EINVAL;
+}
+
 static int adin_get_tunable(struct phy_device *phydev,
 			    struct ethtool_tunable *tuna, void *data)
 {
···
 		return adin_get_downshift(phydev, data);
 	case ETHTOOL_PHY_EDPD:
 		return adin_get_edpd(phydev, data);
+	case ETHTOOL_PHY_FAST_LINK_DOWN:
+		return adin_get_fast_down(phydev, data);
 	default:
 		return -EOPNOTSUPP;
 	}
···
 		return adin_set_downshift(phydev, *(const u8 *)data);
 	case ETHTOOL_PHY_EDPD:
 		return adin_set_edpd(phydev, *(const u16 *)data);
+	case ETHTOOL_PHY_FAST_LINK_DOWN:
+		return adin_set_fast_down(phydev, data);
 	default:
 		return -EOPNOTSUPP;
 	}