Merge branch 'net-phy-add-open-alliance-tc14-10base-t1s-phy-cable-diagnostic-support'

Parthiban Veerasooran says:

====================
net: phy: Add Open Alliance TC14 10Base-T1S PHY cable diagnostic support

This patch series adds Open Alliance TC14 (OATC14) 10BASE-T1S cable
diagnostic feature support to the Linux kernel PHY subsystem and enable
this feature for Microchip LAN867x Rev.D0 PHYs. These patches provide
standardized cable test functionality for 10BASE-T1S Ethernet PHYs,
allowing users to perform cable diagnostics via ethtool.

Patch Summary:
1. add OATC14 10BASE-T1S PHY cable diagnostic support
	- Implements support for the OATC14 cable diagnostic feature in
	  Clause 45 PHYs.
	- Adds functions to start a cable test and retrieve its status,
	  mapping hardware results to ethtool codes.
	- Exports these functions for use by PHY drivers.
	- Open Alliance TC14 10BASE-T1S Advanced Diagnostic PHY Features.
	  https://opensig.org/wp-content/uploads/2025/06/OPEN_Alliance_10BASE-T1S_Advanced_PHY_features_for-automotive_Ethernet_V2.1b.pdf

2. add cable diagnostic support for LAN867x Rev.D0
	- Integrates the generic OATC14 cable test functions into the
	  Microchip LAN867x Rev.D0 PHY driver.
	- Enables ethtool cable diagnostics for this PHY, improving
	  troubleshooting and maintenance.
====================

Link: https://patch.msgid.link/20251105051213.50443-1-parthiban.veerasooran@microchip.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

4 files changed, 163 insertions, 0 deletions

diff --git a/drivers/net/phy/mdio-open-alliance.h b/drivers/net/phy/mdio-open-alliance.h
index 931e14660d75..6850a3f0b31e 100644
--- a/drivers/net/phy/mdio-open-alliance.h
+++ b/drivers/net/phy/mdio-open-alliance.h
@@ -43,4 +43,40 @@
 /* Version Identifiers */
 #define OATC14_IDM		0x0a00
 
+/*
+ * Open Alliance TC14 (10BASE-T1S) - Advanced Diagnostic Features Registers
+ *
+ * Refer to the OPEN Alliance documentation:
+ *   https://opensig.org/automotive-ethernet-specifications/
+ *
+ * Specification:
+ *   "10BASE-T1S Advanced Diagnostic PHY Features"
+ *   https://opensig.org/wp-content/uploads/2025/06/OPEN_Alliance_10BASE-T1S_Advanced_PHY_features_for-automotive_Ethernet_V2.1b.pdf
+ */
+/* Advanced Diagnostic Features Capability Register*/
+#define MDIO_OATC14_ADFCAP		0xcc00
+#define OATC14_ADFCAP_HDD_CAPABILITY	GENMASK(10, 8)
+
+/* Harness Defect Detection Register */
+#define MDIO_OATC14_HDD			0xcc01
+#define OATC14_HDD_CONTROL		BIT(15)
+#define OATC14_HDD_READY		BIT(14)
+#define OATC14_HDD_START_CONTROL	BIT(13)
+#define OATC14_HDD_VALID		BIT(2)
+#define OATC14_HDD_SHORT_OPEN_STATUS	GENMASK(1, 0)
+
+/* Bus Short/Open Status:
+ * 0 0 - no fault; everything is ok. (Default)
+ * 0 1 - detected as an open or missing termination(s)
+ * 1 0 - detected as a short or extra termination(s)
+ * 1 1 - fault but fault type not detectable. More details can be available by
+ *       vender specific register if supported.
+ */
+enum oatc14_hdd_status {
+	OATC14_HDD_STATUS_CABLE_OK = 0,
+	OATC14_HDD_STATUS_OPEN,
+	OATC14_HDD_STATUS_SHORT,
+	OATC14_HDD_STATUS_NOT_DETECTABLE,
+};
+
 #endif /* __MDIO_OPEN_ALLIANCE__ */
diff --git a/drivers/net/phy/microchip_t1s.c b/drivers/net/phy/microchip_t1s.c
index bce5cf087b19..5a0a66778977 100644
--- a/drivers/net/phy/microchip_t1s.c
+++ b/drivers/net/phy/microchip_t1s.c
@@ -573,6 +573,8 @@ static struct phy_driver microchip_t1s_driver[] = {
 		.get_plca_cfg	    = genphy_c45_plca_get_cfg,
 		.set_plca_cfg	    = lan86xx_plca_set_cfg,
 		.get_plca_status    = genphy_c45_plca_get_status,
+		.cable_test_start   = genphy_c45_oatc14_cable_test_start,
+		.cable_test_get_status = genphy_c45_oatc14_cable_test_get_status,
 	},
 	{
 		PHY_ID_MATCH_EXACT(PHY_ID_LAN865X_REVB),
diff --git a/drivers/net/phy/phy-c45.c b/drivers/net/phy/phy-c45.c
index 1a7b32be4625..e8e5be4684ab 100644
--- a/drivers/net/phy/phy-c45.c
+++ b/drivers/net/phy/phy-c45.c
@@ -7,6 +7,7 @@
 #include <linux/mdio.h>
 #include <linux/mii.h>
 #include <linux/phy.h>
+#include <linux/ethtool_netlink.h>
 
 #include "mdio-open-alliance.h"
 #include "phylib-internal.h"
@@ -1573,3 +1574,124 @@ int genphy_c45_ethtool_set_eee(struct phy_device *phydev,
 	return ret;
 }
 EXPORT_SYMBOL(genphy_c45_ethtool_set_eee);
+
+/**
+ * oatc14_cable_test_get_result_code - Convert hardware cable test status to
+ *                                     ethtool result code.
+ * @status: The hardware-reported cable test status
+ *
+ * This helper function maps the OATC14 HDD cable test status to the
+ * corresponding ethtool cable test result code. It provides a translation
+ * between the device-specific status values and the standardized ethtool
+ * result codes.
+ *
+ * Return:
+ * * ETHTOOL_A_CABLE_RESULT_CODE_OK          - Cable is OK
+ * * ETHTOOL_A_CABLE_RESULT_CODE_OPEN        - Open circuit detected
+ * * ETHTOOL_A_CABLE_RESULT_CODE_SAME_SHORT  - Short circuit detected
+ * * ETHTOOL_A_CABLE_RESULT_CODE_UNSPEC      - Status not detectable or invalid
+ */
+static int oatc14_cable_test_get_result_code(enum oatc14_hdd_status status)
+{
+	switch (status) {
+	case OATC14_HDD_STATUS_CABLE_OK:
+		return ETHTOOL_A_CABLE_RESULT_CODE_OK;
+	case OATC14_HDD_STATUS_OPEN:
+		return ETHTOOL_A_CABLE_RESULT_CODE_OPEN;
+	case OATC14_HDD_STATUS_SHORT:
+		return ETHTOOL_A_CABLE_RESULT_CODE_SAME_SHORT;
+	case OATC14_HDD_STATUS_NOT_DETECTABLE:
+	default:
+		return ETHTOOL_A_CABLE_RESULT_CODE_UNSPEC;
+	}
+}
+
+/**
+ * genphy_c45_oatc14_cable_test_get_status - Get status of OATC14 10Base-T1S
+ *                                           PHY cable test.
+ * @phydev:   pointer to the PHY device structure
+ * @finished: pointer to a boolean set true if the test is complete
+ *
+ * Retrieves the current status of the OATC14 10Base-T1S PHY cable test.
+ * This function reads the OATC14 HDD register to determine whether the test
+ * results are valid and whether the test has finished.
+ *
+ * If the test is complete, the function reports the cable test result via
+ * the ethtool cable test interface using ethnl_cable_test_result(), and then
+ * clears the test control bit in the PHY register to reset the test state.
+ *
+ * Return: 0 on success, or a negative error code on failure (e.g. register
+ *         read/write error).
+ */
+int genphy_c45_oatc14_cable_test_get_status(struct phy_device *phydev,
+					    bool *finished)
+{
+	int ret;
+	u8 sts;
+
+	*finished = false;
+
+	ret = phy_read_mmd(phydev, MDIO_MMD_VEND2, MDIO_OATC14_HDD);
+	if (ret < 0)
+		return ret;
+
+	if (!(ret & OATC14_HDD_VALID))
+		return 0;
+
+	*finished = true;
+
+	sts = FIELD_GET(OATC14_HDD_SHORT_OPEN_STATUS, ret);
+
+	ret = ethnl_cable_test_result(phydev, ETHTOOL_A_CABLE_PAIR_A,
+				      oatc14_cable_test_get_result_code(sts));
+	if (ret)
+		return ret;
+
+	return phy_clear_bits_mmd(phydev, MDIO_MMD_VEND2,
+				  MDIO_OATC14_HDD, OATC14_HDD_CONTROL);
+}
+EXPORT_SYMBOL(genphy_c45_oatc14_cable_test_get_status);
+
+/**
+ * genphy_c45_oatc14_cable_test_start - Start a cable test on an OATC14
+ *                                      10Base-T1S PHY.
+ * @phydev: Pointer to the PHY device structure
+ *
+ * This function initiates a cable diagnostic test on a Clause 45 OATC14
+ * 10Base-T1S capable PHY device. It first reads the PHY’s advanced diagnostic
+ * capability register to check if High Definition Diagnostics (HDD) mode is
+ * supported. If the PHY does not report HDD capability, cable testing is not
+ * supported and the function returns -EOPNOTSUPP.
+ *
+ * For PHYs that support HDD, the function sets the appropriate control bits in
+ * the OATC14_HDD register to enable and start the cable diagnostic test.
+ *
+ * Return:
+ * * 0 on success
+ * * -EOPNOTSUPP if the PHY does not support HDD capability
+ * * A negative error code on I/O or register access failures
+ */
+int genphy_c45_oatc14_cable_test_start(struct phy_device *phydev)
+{
+	int ret;
+
+	ret = phy_read_mmd(phydev, MDIO_MMD_VEND2, MDIO_OATC14_ADFCAP);
+	if (ret < 0)
+		return ret;
+
+	if (!(ret & OATC14_ADFCAP_HDD_CAPABILITY))
+		return -EOPNOTSUPP;
+
+	ret = phy_set_bits_mmd(phydev, MDIO_MMD_VEND2, MDIO_OATC14_HDD,
+			       OATC14_HDD_CONTROL);
+	if (ret)
+		return ret;
+
+	ret = phy_read_mmd(phydev, MDIO_MMD_VEND2, MDIO_OATC14_HDD);
+	if (ret < 0)
+		return ret;
+
+	return phy_set_bits_mmd(phydev, MDIO_MMD_VEND2, MDIO_OATC14_HDD,
+				OATC14_HDD_START_CONTROL);
+}
+EXPORT_SYMBOL(genphy_c45_oatc14_cable_test_start);
diff --git a/include/linux/phy.h b/include/linux/phy.h
index d145a200ea21..bf5457341ca8 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -2251,6 +2251,9 @@ int genphy_c45_ethtool_get_eee(struct phy_device *phydev,
 int genphy_c45_ethtool_set_eee(struct phy_device *phydev,
 			       struct ethtool_keee *data);
 int genphy_c45_an_config_eee_aneg(struct phy_device *phydev);
+int genphy_c45_oatc14_cable_test_start(struct phy_device *phydev);
+int genphy_c45_oatc14_cable_test_get_status(struct phy_device *phydev,
+					    bool *finished);
 
 /* The gen10g_* functions are the old Clause 45 stub */
 int gen10g_config_aneg(struct phy_device *phydev);