net: phy: marvell: implement cable-test for 88E308X/88E609X family

This commit implements VCT in 88E308X/88E609X Family.

It require two workarounds with some magic configuration.
Regular use require only one register configuration. But Open Circuit
require second workaround.
It cause implementation two phases for fault length measuring.

Fast Ethernet PHY have implemented very simple version of VCT. It's
complitley different than vct5 or vct7.

Signed-off-by: Pawel Dembicki <paweldembicki@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/20240402201123.2961909-3-paweldembicki@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: CHKDSK88

drivers/net/phy/marvell.c

@@ -279,6 +279,23 @@
 #define MII_VCT7_CTRL_METERS			BIT(10)
 #define MII_VCT7_CTRL_CENTIMETERS		0
 
+#define MII_VCT_TXPINS			0x1A
+#define MII_VCT_RXPINS			0x1B
+#define MII_VCT_TXPINS_ENVCT		BIT(15)
+#define MII_VCT_TXRXPINS_VCTTST		GENMASK(14, 13)
+#define MII_VCT_TXRXPINS_VCTTST_SHIFT	13
+#define MII_VCT_TXRXPINS_VCTTST_OK	0
+#define MII_VCT_TXRXPINS_VCTTST_SHORT	1
+#define MII_VCT_TXRXPINS_VCTTST_OPEN	2
+#define MII_VCT_TXRXPINS_VCTTST_FAIL	3
+#define MII_VCT_TXRXPINS_AMPRFLN	GENMASK(12, 8)
+#define MII_VCT_TXRXPINS_AMPRFLN_SHIFT	8
+#define MII_VCT_TXRXPINS_DISTRFLN	GENMASK(7, 0)
+#define MII_VCT_TXRXPINS_DISTRFLN_MAX	0xff
+
+#define M88E3082_PAIR_A		BIT(0)
+#define M88E3082_PAIR_B		BIT(1)
+
 #define LPA_PAUSE_FIBER		0x180
 #define LPA_PAUSE_ASYM_FIBER	0x100
 
@@ -301,6 +318,12 @@ static struct marvell_hw_stat marvell_hw_stats[] = {
 	{ "phy_receive_errors_fiber", 1, 21, 16},
 };
 
+enum {
+	M88E3082_VCT_OFF,
+	M88E3082_VCT_PHASE1,
+	M88E3082_VCT_PHASE2,
+};
+
 struct marvell_priv {
 	u64 stats[ARRAY_SIZE(marvell_hw_stats)];
 	char *hwmon_name;
@@ -310,6 +333,7 @@ struct marvell_priv {
 	u32 last;
 	u32 step;
 	s8 pair;
+	u8 vct_phase;
 };
 
 static int marvell_read_page(struct phy_device *phydev)
@@ -2417,6 +2441,188 @@ static int marvell_vct7_cable_test_get_status(struct phy_device *phydev,
 	return 0;
 }
 
+static int m88e3082_vct_cable_test_start(struct phy_device *phydev)
+{
+	struct marvell_priv *priv = phydev->priv;
+	int ret;
+
+	/* It needs some magic workarounds described in VCT manual for this PHY.
+	 */
+	ret = phy_write(phydev, 29, 0x0003);
+	if (ret < 0)
+		return ret;
+
+	ret = phy_write(phydev, 30, 0x6440);
+	if (ret < 0)
+		return ret;
+
+	if (priv->vct_phase == M88E3082_VCT_PHASE1) {
+		ret = phy_write(phydev, 29, 0x000a);
+		if (ret < 0)
+			return ret;
+
+		ret = phy_write(phydev, 30, 0x0002);
+		if (ret < 0)
+			return ret;
+	}
+
+	ret = phy_write(phydev, MII_BMCR,
+			BMCR_RESET | BMCR_SPEED100 | BMCR_FULLDPLX);
+	if (ret < 0)
+		return ret;
+
+	ret = phy_write(phydev, MII_VCT_TXPINS, MII_VCT_TXPINS_ENVCT);
+	if (ret < 0)
+		return ret;
+
+	ret = phy_write(phydev, 29, 0x0003);
+	if (ret < 0)
+		return ret;
+
+	ret = phy_write(phydev, 30, 0x0);
+	if (ret < 0)
+		return ret;
+
+	if (priv->vct_phase == M88E3082_VCT_OFF) {
+		priv->vct_phase = M88E3082_VCT_PHASE1;
+		priv->pair = 0;
+
+		return 0;
+	}
+
+	ret = phy_write(phydev, 29, 0x000a);
+	if (ret < 0)
+		return ret;
+
+	ret = phy_write(phydev, 30, 0x0);
+	if (ret < 0)
+		return ret;
+
+	priv->vct_phase = M88E3082_VCT_PHASE2;
+
+	return 0;
+}
+
+static int m88e3082_vct_cable_test_report_trans(int result, u8 distance)
+{
+	switch (result) {
+	case MII_VCT_TXRXPINS_VCTTST_OK:
+		if (distance == MII_VCT_TXRXPINS_DISTRFLN_MAX)
+			return ETHTOOL_A_CABLE_RESULT_CODE_OK;
+		return ETHTOOL_A_CABLE_RESULT_CODE_IMPEDANCE_MISMATCH;
+	case MII_VCT_TXRXPINS_VCTTST_SHORT:
+		return ETHTOOL_A_CABLE_RESULT_CODE_SAME_SHORT;
+	case MII_VCT_TXRXPINS_VCTTST_OPEN:
+		return ETHTOOL_A_CABLE_RESULT_CODE_OPEN;
+	default:
+		return ETHTOOL_A_CABLE_RESULT_CODE_UNSPEC;
+	}
+}
+
+static u32 m88e3082_vct_distrfln_2_cm(u8 distrfln)
+{
+	if (distrfln < 24)
+		return 0;
+
+	/* Original function for meters: y = 0.7861x - 18.862 */
+	return (7861 * distrfln - 188620) / 100;
+}
+
+static int m88e3082_vct_cable_test_get_status(struct phy_device *phydev,
+					      bool *finished)
+{
+	u8 tx_vcttst_res, rx_vcttst_res, tx_distrfln, rx_distrfln;
+	struct marvell_priv *priv = phydev->priv;
+	int ret, tx_result, rx_result;
+	bool done_phase = true;
+
+	*finished = false;
+
+	ret = phy_read(phydev, MII_VCT_TXPINS);
+	if (ret < 0)
+		return ret;
+	else if (ret & MII_VCT_TXPINS_ENVCT)
+		return 0;
+
+	tx_distrfln = ret & MII_VCT_TXRXPINS_DISTRFLN;
+	tx_vcttst_res = (ret & MII_VCT_TXRXPINS_VCTTST) >>
+			MII_VCT_TXRXPINS_VCTTST_SHIFT;
+
+	ret = phy_read(phydev, MII_VCT_RXPINS);
+	if (ret < 0)
+		return ret;
+
+	rx_distrfln = ret & MII_VCT_TXRXPINS_DISTRFLN;
+	rx_vcttst_res = (ret & MII_VCT_TXRXPINS_VCTTST) >>
+			MII_VCT_TXRXPINS_VCTTST_SHIFT;
+
+	*finished = true;
+
+	switch (priv->vct_phase) {
+	case M88E3082_VCT_PHASE1:
+		tx_result = m88e3082_vct_cable_test_report_trans(tx_vcttst_res,
+								 tx_distrfln);
+		rx_result = m88e3082_vct_cable_test_report_trans(rx_vcttst_res,
+								 rx_distrfln);
+
+		ethnl_cable_test_result(phydev, ETHTOOL_A_CABLE_PAIR_A,
+					tx_result);
+		ethnl_cable_test_result(phydev, ETHTOOL_A_CABLE_PAIR_B,
+					rx_result);
+
+		if (tx_vcttst_res == MII_VCT_TXRXPINS_VCTTST_OPEN) {
+			done_phase = false;
+			priv->pair |= M88E3082_PAIR_A;
+		} else if (tx_distrfln < MII_VCT_TXRXPINS_DISTRFLN_MAX) {
+			u8 pair = ETHTOOL_A_CABLE_PAIR_A;
+			u32 cm = m88e3082_vct_distrfln_2_cm(tx_distrfln);
+
+			ethnl_cable_test_fault_length(phydev, pair, cm);
+		}
+
+		if (rx_vcttst_res == MII_VCT_TXRXPINS_VCTTST_OPEN) {
+			done_phase = false;
+			priv->pair |= M88E3082_PAIR_B;
+		} else if (rx_distrfln < MII_VCT_TXRXPINS_DISTRFLN_MAX) {
+			u8 pair = ETHTOOL_A_CABLE_PAIR_B;
+			u32 cm = m88e3082_vct_distrfln_2_cm(rx_distrfln);
+
+			ethnl_cable_test_fault_length(phydev, pair, cm);
+		}
+
+		break;
+	case M88E3082_VCT_PHASE2:
+		if (priv->pair & M88E3082_PAIR_A &&
+		    tx_vcttst_res == MII_VCT_TXRXPINS_VCTTST_OPEN &&
+		    tx_distrfln < MII_VCT_TXRXPINS_DISTRFLN_MAX) {
+			u8 pair = ETHTOOL_A_CABLE_PAIR_A;
+			u32 cm = m88e3082_vct_distrfln_2_cm(tx_distrfln);
+
+			ethnl_cable_test_fault_length(phydev, pair, cm);
+		}
+		if (priv->pair & M88E3082_PAIR_B &&
+		    rx_vcttst_res == MII_VCT_TXRXPINS_VCTTST_OPEN &&
+		    rx_distrfln < MII_VCT_TXRXPINS_DISTRFLN_MAX) {
+			u8 pair = ETHTOOL_A_CABLE_PAIR_B;
+			u32 cm = m88e3082_vct_distrfln_2_cm(rx_distrfln);
+
+			ethnl_cable_test_fault_length(phydev, pair, cm);
+		}
+
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	if (!done_phase) {
+		*finished = false;
+		return m88e3082_vct_cable_test_start(phydev);
+	}
+	if (*finished)
+		priv->vct_phase = M88E3082_VCT_OFF;
+	return 0;
+}
+
 #ifdef CONFIG_HWMON
 struct marvell_hwmon_ops {
 	int (*config)(struct phy_device *phydev);
@@ -3300,6 +3506,8 @@ static struct phy_driver marvell_drivers[] = {
 		.read_status = marvell_read_status,
 		.resume = genphy_resume,
 		.suspend = genphy_suspend,
+		.cable_test_start = m88e3082_vct_cable_test_start,
+		.cable_test_get_status = m88e3082_vct_cable_test_get_status,
 	},
 	{
 		.phy_id = MARVELL_PHY_ID_88E1112,