Add TDR cable test support for the internal YT861x PHYs, reporting the
per-pair result and the fault length.

Signed-off-by: David Yang <mmyangfl@gmail.com>
---
 drivers/net/phy/motorcomm.c | 113 ++++++++++++++++++++++++++++++++++++
 1 file changed, 113 insertions(+)

diff --git a/drivers/net/phy/motorcomm.c b/drivers/net/phy/motorcomm.c
index 7078c4a0225d..463e1ea3efc9 100644
--- a/drivers/net/phy/motorcomm.c
+++ b/drivers/net/phy/motorcomm.c
@@ -8,6 +8,7 @@
 
 #include <linux/clk.h>
 #include <linux/etherdevice.h>
+#include <linux/ethtool_netlink.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/phy.h>
@@ -300,6 +301,19 @@
 #define YT8531_SCR_CLK_SRC_REF_25M		4
 #define YT8531_SCR_CLK_SRC_SSC_25M		5
 
+/* TDR (cable diagnostic) test control */
+#define YT861X_TDR_CTRL_REG			0x80
+#define YT861X_TDR_CTRL_START			BIT(0)
+
+#define YT861X_TDR_STATUS_REG			0x84
+#define YT861X_TDR_STATUS_BUSY			BIT(15)
+#define YT861X_TDR_STATUS_PAIR_OK		0
+#define YT861X_TDR_STATUS_PAIR_UNKNOWN		1
+#define YT861X_TDR_STATUS_PAIR_SHORT		2
+#define YT861X_TDR_STATUS_PAIR_OPEN		3
+
+#define YT861X_TDR_PAIR_LENGTH_REG(n)		(0x87 + (n))	/* in cm */
+
 #define YT8821_SDS_EXT_CSR_CTRL_REG			0x23
 #define YT8821_SDS_EXT_CSR_VCO_LDO_EN			BIT(15)
 #define YT8821_SDS_EXT_CSR_VCO_BIAS_LPF_EN		BIT(8)
@@ -2563,6 +2577,103 @@ static int yt861x_config_init(struct phy_device *phydev)
 					 sleep ? YT8521_ESC1R_SLEEP_SW : 0);
 }
 
+/**
+ * yt861x_cable_test_start() - start a cable diagnostic (TDR) test
+ * @phydev: a pointer to a &struct phy_device
+ *
+ * Returns: 0 or negative errno code
+ */
+static int yt861x_cable_test_start(struct phy_device *phydev)
+{
+	int ret;
+
+	/* auto sleep would abort the TDR test */
+	ret = ytphy_modify_ext_with_lock(phydev,
+					 YT8521_EXTREG_SLEEP_CONTROL1_REG,
+					 YT8521_ESC1R_SLEEP_SW, 0);
+	if (ret)
+		return ret;
+
+	ret = ytphy_write_ext_with_lock(phydev, YT861X_TDR_CTRL_REG,
+					YT861X_TDR_CTRL_START);
+	if (ret) {
+		int err = yt861x_config_init(phydev);
+
+		if (err)
+			phydev_warn(phydev,
+				    "Failed to restore auto sleep: %d\n",
+				    err);
+	}
+
+	return ret;
+}
+
+/**
+ * yt861x_cable_test_get_status() - report cable diagnostic test results
+ * @phydev: a pointer to a &struct phy_device
+ * @finished: set to true when the test is complete
+ *
+ * Returns: 0 or negative errno code
+ */
+static int yt861x_cable_test_get_status(struct phy_device *phydev,
+					bool *finished)
+{
+	int status;
+	int ret;
+
+	*finished = false;
+
+	status = ytphy_read_ext_with_lock(phydev, YT861X_TDR_STATUS_REG);
+	if (status < 0)
+		return status;
+
+	if (status & YT861X_TDR_STATUS_BUSY)
+		return 0;
+
+	for (int pair = ETHTOOL_A_CABLE_PAIR_A; pair <= ETHTOOL_A_CABLE_PAIR_D;
+	     pair++) {
+		u8 code;
+
+		switch ((status >> (2 * pair)) & 0x3) {
+		case YT861X_TDR_STATUS_PAIR_OK:
+			code = ETHTOOL_A_CABLE_RESULT_CODE_OK;
+			break;
+		case YT861X_TDR_STATUS_PAIR_SHORT:
+			code = ETHTOOL_A_CABLE_RESULT_CODE_SAME_SHORT;
+			break;
+		case YT861X_TDR_STATUS_PAIR_OPEN:
+			code = ETHTOOL_A_CABLE_RESULT_CODE_OPEN;
+			break;
+		default:
+			code = ETHTOOL_A_CABLE_RESULT_CODE_UNSPEC;
+		}
+
+		ethnl_cable_test_result(phydev, pair, code);
+
+		if (code != ETHTOOL_A_CABLE_RESULT_CODE_OK &&
+		    code != ETHTOOL_A_CABLE_RESULT_CODE_UNSPEC) {
+			ret = ytphy_read_ext_with_lock(phydev,
+						       YT861X_TDR_PAIR_LENGTH_REG(pair));
+			if (ret >= 0)
+				ethnl_cable_test_fault_length(phydev, pair,
+							      ret);
+		}
+	}
+
+	/* the reset below does not restore auto sleep by itself */
+	ret = yt861x_config_init(phydev);
+	if (ret)
+		return ret;
+
+	ret = genphy_soft_reset(phydev);
+	if (ret)
+		return ret;
+
+	*finished = true;
+
+	return 0;
+}
+
 /**
  * yt8821_get_features - read mmd register to get 2.5G capability
  * @phydev: target phy_device struct
@@ -3206,6 +3317,8 @@ static struct phy_driver motorcomm_phy_drvs[] = {
 		.soft_reset		= genphy_soft_reset,
 		.suspend		= genphy_suspend,
 		.resume			= genphy_resume,
+		.cable_test_start	= yt861x_cable_test_start,
+		.cable_test_get_status	= yt861x_cable_test_get_status,
 	},
 	{
 		PHY_ID_MATCH_EXACT(PHY_ID_YT8821),
-- 
2.53.0