[PATCH net-next v3 3/3] net: phy: dp83tg720: Add cable testing support

Oleksij Rempel
2024-08-09T07:24:51Z

Introduce cable testing support for the DP83TG720 PHY. This implementation
is based on the "DP83TG720S-Q1: Configuring for Open Alliance Specification
Compliance (Rev. B)" application note.

The feature has been tested with cables of various lengths:
- No cable: 1m till open reported.
- 5 meter cable: reported properly.
- 20 meter cable: reported as 19m.
- 40 meter cable: reported as cable ok.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
---
changes v3:
- select OPEN_ALLIANCE_HELPERS
changes v2:
- use open alliance specific helpers for the TDR results
---
drivers/net/phy/Kconfig | 1 +
drivers/net/phy/dp83tg720.c | 154 ++++++++++++++++++++++++++++++++++++
2 files changed, 155 insertions(+)

diff --git a/drivers/net/phy/Kconfig b/drivers/net/phy/Kconfig
index 874422e530ff0..f530fcd092fe4 100644
--- a/drivers/net/phy/Kconfig
+++ b/drivers/net/phy/Kconfig
@@ -417,6 +417,7 @@ config DP83TD510_PHY

config DP83TG720_PHY
tristate "Texas Instruments DP83TG720 Ethernet 1000Base-T1 PHY"
+ select OPEN_ALLIANCE_HELPERS
help
The DP83TG720S-Q1 is an automotive Ethernet physical layer
transceiver compliant with IEEE 802.3bp and Open Alliance
diff --git a/drivers/net/phy/dp83tg720.c b/drivers/net/phy/dp83tg720.c
index c706429b225a2..0ef4d7dba0656 100644
--- a/drivers/net/phy/dp83tg720.c
+++ b/drivers/net/phy/dp83tg720.c
@@ -3,10 +3,13 @@
* Copyright (c) 2023 Pengutronix, Oleksij Rempel <kernel@pengutronix.de>
*/
#include <linux/bitfield.h>
+#include <linux/ethtool_netlink.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/phy.h>

+#include "open_alliance_helpers.h"
+
#define DP83TG720S_PHY_ID 0x2000a284

/* MDIO_MMD_VEND2 registers */
@@ -14,6 +17,17 @@
#define DP83TG720S_STS_MII_INT BIT(7)
#define DP83TG720S_LINK_STATUS BIT(0)

+/* TDR Configuration Register (0x1E) */
+#define DP83TG720S_TDR_CFG 0x1e
+/* 1b = TDR start, 0b = No TDR */
+#define DP83TG720S_TDR_START BIT(15)
+/* 1b = TDR auto on link down, 0b = Manual TDR start */
+#define DP83TG720S_CFG_TDR_AUTO_RUN BIT(14)
+/* 1b = TDR done, 0b = TDR in progress */
+#define DP83TG720S_TDR_DONE BIT(1)
+/* 1b = TDR fail, 0b = TDR success */
+#define DP83TG720S_TDR_FAIL BIT(0)
+
#define DP83TG720S_PHY_RESET 0x1f
#define DP83TG720S_HW_RESET BIT(15)

@@ -22,18 +36,155 @@
/* Power Mode 0 is Normal mode */
#define DP83TG720S_LPS_CFG3_PWR_MODE_0 BIT(0)

+/* Open Aliance 1000BaseT1 compatible HDD.TDR Fault Status Register */
+#define DP83TG720S_TDR_FAULT_STATUS 0x30f
+
+/* Register 0x0301: TDR Configuration 2 */
+#define DP83TG720S_TDR_CFG2 0x301
+
+/* Register 0x0303: TDR Configuration 3 */
+#define DP83TG720S_TDR_CFG3 0x303
+
+/* Register 0x0304: TDR Configuration 4 */
+#define DP83TG720S_TDR_CFG4 0x304
+
+/* Register 0x0405: Unknown Register */
+#define DP83TG720S_UNKNOWN_0405 0x405
+
+/* Register 0x0576: TDR Master Link Down Control */
+#define DP83TG720S_TDR_MASTER_LINK_DOWN 0x576
+
#define DP83TG720S_RGMII_DELAY_CTRL 0x602
/* In RGMII mode, Enable or disable the internal delay for RXD */
#define DP83TG720S_RGMII_RX_CLK_SEL BIT(1)
/* In RGMII mode, Enable or disable the internal delay for TXD */
#define DP83TG720S_RGMII_TX_CLK_SEL BIT(0)

+/* Register 0x083F: Unknown Register */
+#define DP83TG720S_UNKNOWN_083F 0x83f
+
#define DP83TG720S_SQI_REG_1 0x871
#define DP83TG720S_SQI_OUT_WORST GENMASK(7, 5)
#define DP83TG720S_SQI_OUT GENMASK(3, 1)

#define DP83TG720_SQI_MAX 7

+/**
+ * dp83tg720_cable_test_start - Start the cable test for the DP83TG720 PHY.
+ * @phydev: Pointer to the phy_device structure.
+ *
+ * This sequence is based on the documented procedure for the DP83TG720 PHY.
+ *
+ * Returns: 0 on success, a negative error code on failure.
+ */
+static int dp83tg720_cable_test_start(struct phy_device *phydev)
+{
+ int ret;
+
+ /* Initialize the PHY to run the TDR test as described in the
+ * "DP83TG720S-Q1: Configuring for Open Alliance Specification
+ * Compliance (Rev. B)" application note.
+ * Most of the registers are not documented. Some of register names
+ * are guessed by comparing the register offsets with the DP83TD510E.
+ */
+
+ /* Force master link down */
+ ret = phy_set_bits_mmd(phydev, MDIO_MMD_VEND2,
+ DP83TG720S_TDR_MASTER_LINK_DOWN, 0x0400);
+ if (ret)
+ return ret;
+
+ ret = phy_write_mmd(phydev, MDIO_MMD_VEND2, DP83TG720S_TDR_CFG2,
+ 0xa008);
+ if (ret)
+ return ret;
+
+ ret = phy_write_mmd(phydev, MDIO_MMD_VEND2, DP83TG720S_TDR_CFG3,
+ 0x0928);
+ if (ret)
+ return ret;
+
+ ret = phy_write_mmd(phydev, MDIO_MMD_VEND2, DP83TG720S_TDR_CFG4,
+ 0x0004);
+ if (ret)
+ return ret;
+
+ ret = phy_write_mmd(phydev, MDIO_MMD_VEND2, DP83TG720S_UNKNOWN_0405,
+ 0x6400);
+ if (ret)
+ return ret;
+
+ ret = phy_write_mmd(phydev, MDIO_MMD_VEND2, DP83TG720S_UNKNOWN_083F,
+ 0x3003);
+ if (ret)
+ return ret;
+
+ /* Start the TDR */
+ ret = phy_set_bits_mmd(phydev, MDIO_MMD_VEND2, DP83TG720S_TDR_CFG,
+ DP83TG720S_TDR_START);
+ if (ret)
+ return ret;
+
+ return 0;
+}
+
+/**
+ * dp83tg720_cable_test_get_status - Get the status of the cable test for the
+ * DP83TG720 PHY.
+ * @phydev: Pointer to the phy_device structure.
+ * @finished: Pointer to a boolean that indicates whether the test is finished.
+ *
+ * The function sets the @finished flag to true if the test is complete.
+ *
+ * Returns: 0 on success or a negative error code on failure.
+ */
+static int dp83tg720_cable_test_get_status(struct phy_device *phydev,
+ bool *finished)
+{
+ int ret, stat;
+
+ *finished = false;
+
+ /* Read the TDR status */
+ ret = phy_read_mmd(phydev, MDIO_MMD_VEND2, DP83TG720S_TDR_CFG);
+ if (ret < 0)
+ return ret;
+
+ /* Check if the TDR test is done */
+ if (!(ret & DP83TG720S_TDR_DONE))
+ return 0;
+
+ /* Check for TDR test failure */
+ if (!(ret & DP83TG720S_TDR_FAIL)) {
+ int location;
+
+ /* Read fault status */
+ ret = phy_read_mmd(phydev, MDIO_MMD_VEND2,
+ DP83TG720S_TDR_FAULT_STATUS);
+ if (ret < 0)
+ return ret;
+
+ /* Get fault type */
+ stat = oa_1000bt1_get_ethtool_cable_result_code(ret);
+
+ /* Determine fault location */
+ location = oa_1000bt1_get_tdr_distance(ret);
+ if (location > 0)
+ ethnl_cable_test_fault_length(phydev,
+ ETHTOOL_A_CABLE_PAIR_A,
+ location);
+ } else {
+ /* Active link partner or other issues */
+ stat = ETHTOOL_A_CABLE_RESULT_CODE_UNSPEC;
+ }
+
+ *finished = true;
+
+ ethnl_cable_test_result(phydev, ETHTOOL_A_CABLE_PAIR_A, stat);
+
+ return phy_init_hw(phydev);
+}
+
static int dp83tg720_config_aneg(struct phy_device *phydev)
{
int ret;
@@ -195,12 +346,15 @@ static struct phy_driver dp83tg720_driver[] = {
PHY_ID_MATCH_MODEL(DP83TG720S_PHY_ID),
.name = "TI DP83TG720S",

+ .flags = PHY_POLL_CABLE_TEST,
.config_aneg = dp83tg720_config_aneg,
.read_status = dp83tg720_read_status,
.get_features = genphy_c45_pma_read_ext_abilities,
.config_init = dp83tg720_config_init,
.get_sqi = dp83tg720_get_sqi,
.get_sqi_max = dp83tg720_get_sqi_max,
+ .cable_test_start = dp83tg720_cable_test_start,
+ .cable_test_get_status = dp83tg720_cable_test_get_status,

.suspend = genphy_suspend,
.resume = genphy_resume,
--
2.39.2