[RFC PATCH v1 8/9] net: phy: micrel: ksz886x/ksz8081: add cabletest support

[Oleksij Rempel]

This patch support for cable test for the ksz886x switches and the
ksz8081 PHY.

The patch was tested on a KSZ8873RLL switch with following results:

- port 1:
  - cannot detect any distance
  - provides inverted values
    (Errata: DS80000830A: "LinkMD does not work on Port 1",
     http://ww1.microchip.com/downloads/en/DeviceDoc/KSZ8873-Errata-DS80000830A.pdf)
    - Reports "short" on open or ok.
    - Reports "ok" on short.

- port 2:
  - can detect distance
  - can detect open on each wire of pair A (wire 1 and 2)
  - can detect open only on one wire of pair B (only wire 3)
  - can detect short between wires of a pair (wires 1 + 2 or 3 + 6)
  - short between pairs is detected as open.
    For example short between wires 2 + 3 is detected as open.

In order to work around the errata for port 1, the ksz8795 switch driver
should be extended to provide proper device tree support for the related
PHY nodes. So we can set a DT property to mark the port 1 as affected by
the errata.

Signed-off-by: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>

---

- added PHY_POLL_CABLE_TEST to make it work in interrupt mode
---
 drivers/net/phy/micrel.c | 177 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 177 insertions(+)

diff --git a/drivers/net/phy/micrel.c b/drivers/net/phy/micrel.c
index 47fa8b02630a..f0ca7b53bcf9 100644
--- a/drivers/net/phy/micrel.c
+++ b/drivers/net/phy/micrel.c
@@ -20,6 +20,7 @@
  */
 
 #include <linux/bitfield.h>
+#include <linux/ethtool_netlink.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/phy.h>
@@ -66,6 +67,18 @@
 #define	KSZPHY_INTCS_STATUS			(KSZPHY_INTCS_LINK_DOWN_STATUS |\
 						 KSZPHY_INTCS_LINK_UP_STATUS)
 
+/* LinkMD Control/Status */
+#define KSZ8081_LMD				0x1d
+#define KSZ8081_LMD_ENABLE_TEST			BIT(15)
+#define KSZ8081_LMD_STAT_NORMAL			0
+#define KSZ8081_LMD_STAT_OPEN			1
+#define KSZ8081_LMD_STAT_SHORT			2
+#define KSZ8081_LMD_STAT_FAIL			3
+#define KSZ8081_LMD_STAT_MASK			GENMASK(14, 13)
+/* Short cable (<10 meter) has been detected by LinkMD */
+#define KSZ8081_LMD_SHORT_INDICATOR		BIT(12)
+#define KSZ8081_LMD_DELTA_TIME_MASK		GENMASK(8, 0)
+
 /* PHY Control 1 */
 #define MII_KSZPHY_CTRL_1			0x1e
 #define KSZ8081_CTRL1_MDIX_STAT			BIT(4)
@@ -1399,6 +1412,164 @@ static int kszphy_probe(struct phy_device *phydev)
 	return 0;
 }
 
+static int ksz886x_cable_test_start(struct phy_device *phydev)
+{
+	/* If autoneg is enabled, we won't be able to test cross pair
+	 * short. In this case, the PHY will "detect" a link and
+	 * confuse the internal state machine - disable auto neg here.
+	 * If autoneg is disabled, we should set the speed to 10mbit.
+	 */
+	return phy_clear_bits(phydev, MII_BMCR, BMCR_ANENABLE | BMCR_SPEED100);
+}
+
+static int ksz886x_cable_test_result_trans(u16 status)
+{
+	switch (FIELD_GET(KSZ8081_LMD_STAT_MASK, status)) {
+	case KSZ8081_LMD_STAT_NORMAL:
+		return ETHTOOL_A_CABLE_RESULT_CODE_OK;
+	case KSZ8081_LMD_STAT_SHORT:
+		return ETHTOOL_A_CABLE_RESULT_CODE_SAME_SHORT;
+	case KSZ8081_LMD_STAT_OPEN:
+		return ETHTOOL_A_CABLE_RESULT_CODE_OPEN;
+	case KSZ8081_LMD_STAT_FAIL:
+		/* fall through */
+	default:
+		return ETHTOOL_A_CABLE_RESULT_CODE_UNSPEC;
+	}
+}
+
+static bool ksz886x_cable_test_failed(u16 status)
+{
+	return FIELD_GET(KSZ8081_LMD_STAT_MASK, status) ==
+		KSZ8081_LMD_STAT_FAIL;
+}
+
+static bool ksz886x_cable_test_fault_length_valid(u16 status)
+{
+	switch (FIELD_GET(KSZ8081_LMD_STAT_MASK, status)) {
+	case KSZ8081_LMD_STAT_OPEN:
+		/* fall through */
+	case KSZ8081_LMD_STAT_SHORT:
+		return true;
+	}
+	return false;
+}
+
+static int ksz886x_cable_test_fault_length(u16 status)
+{
+	int dt;
+
+	/* According to the data sheet the distance to the fault is
+	 * DELTA_TIME * 0.4 meters.
+	 */
+	dt = FIELD_GET(KSZ8081_LMD_DELTA_TIME_MASK, status);
+
+	return (dt * 400) / 10;
+}
+
+static int ksz886x_cable_test_wait_for_completion(struct phy_device *phydev)
+{
+	int val, ret;
+
+	ret = phy_read_poll_timeout(phydev, KSZ8081_LMD, val,
+				    !(val & KSZ8081_LMD_ENABLE_TEST),
+				    30000, 100000, true);
+
+	return ret < 0 ? ret : 0;
+}
+
+static int ksz886x_cable_test_one_pair(struct phy_device *phydev, int pair)
+{
+	static const int ethtool_pair[] = {
+		ETHTOOL_A_CABLE_PAIR_A,
+		ETHTOOL_A_CABLE_PAIR_B,
+	};
+	int ret, val, mdix;
+
+	/* There is no way to choice the pair, like we do one ksz9031.
+	 * We can workaround this limitation by using the MDI-X functionality.
+	 */
+	if (pair == 0)
+		mdix = ETH_TP_MDI;
+	else
+		mdix = ETH_TP_MDI_X;
+
+	switch (phydev->phy_id & MICREL_PHY_ID_MASK) {
+	case PHY_ID_KSZ8081:
+		ret = ksz8081_config_mdix(phydev, mdix);
+		break;
+	case PHY_ID_KSZ886X:
+		ret = ksz886x_config_mdix(phydev, mdix);
+		break;
+	default:
+		ret = -ENODEV;
+	}
+
+	if (ret)
+		return ret;
+
+	/* Now we are ready to fire. This command will send a 100ns pulse
+	 * to the pair.
+	 */
+	ret = phy_write(phydev, KSZ8081_LMD, KSZ8081_LMD_ENABLE_TEST);
+	if (ret)
+		return ret;
+
+	ret = ksz886x_cable_test_wait_for_completion(phydev);
+	if (ret)
+		return ret;
+
+	val = phy_read(phydev, KSZ8081_LMD);
+	if (val < 0)
+		return val;
+
+	if (ksz886x_cable_test_failed(val))
+		return -EAGAIN;
+
+	ret = ethnl_cable_test_result(phydev, ethtool_pair[pair],
+				      ksz886x_cable_test_result_trans(val));
+	if (ret)
+		return ret;
+
+	if (!ksz886x_cable_test_fault_length_valid(val))
+		return 0;
+
+	return ethnl_cable_test_fault_length(phydev, ethtool_pair[pair],
+					     ksz886x_cable_test_fault_length(val));
+}
+
+static int ksz886x_cable_test_get_status(struct phy_device *phydev,
+					 bool *finished)
+{
+	unsigned long pair_mask = 0x3;
+	int retries = 20;
+	int pair, ret;
+
+	*finished = false;
+
+	/* Try harder if link partner is active */
+	while (pair_mask && retries--) {
+		for_each_set_bit(pair, &pair_mask, 4) {
+			ret = ksz886x_cable_test_one_pair(phydev, pair);
+			if (ret == -EAGAIN)
+				continue;
+			if (ret < 0)
+				return ret;
+			clear_bit(pair, &pair_mask);
+		}
+		/* If link partner is in autonegotiation mode it will send 2ms
+		 * of FLPs with at least 6ms of silence.
+		 * Add 2ms sleep to have better chances to hit this silence.
+		 */
+		if (pair_mask)
+			msleep(2);
+	}
+
+	*finished = true;
+
+	return 0;
+}
+
 static struct phy_driver ksphy_driver[] = {
 {
 	.phy_id		= PHY_ID_KS8737,
@@ -1505,6 +1676,7 @@ static struct phy_driver ksphy_driver[] = {
 	.phy_id		= PHY_ID_KSZ8081,
 	.name		= "Micrel KSZ8081 or KSZ8091",
 	.phy_id_mask	= MICREL_PHY_ID_MASK,
+	.flags		= PHY_POLL_CABLE_TEST,
 	/* PHY_BASIC_FEATURES */
 	.driver_data	= &ksz8081_type,
 	.probe		= kszphy_probe,
@@ -1519,6 +1691,8 @@ static struct phy_driver ksphy_driver[] = {
 	.get_stats	= kszphy_get_stats,
 	.suspend	= kszphy_suspend,
 	.resume		= kszphy_resume,
+	.cable_test_start	= ksz886x_cable_test_start,
+	.cable_test_get_status	= ksz886x_cable_test_get_status,
 }, {
 	.phy_id		= PHY_ID_KSZ8061,
 	.name		= "Micrel KSZ8061",
@@ -1607,11 +1781,14 @@ static struct phy_driver ksphy_driver[] = {
 	.phy_id_mask	= MICREL_PHY_ID_MASK,
 	.name		= "Micrel KSZ8851 Ethernet MAC or KSZ886X Switch",
 	/* PHY_BASIC_FEATURES */
+	.flags		= PHY_POLL_CABLE_TEST,
 	.config_init	= kszphy_config_init,
 	.config_aneg	= ksz886x_config_aneg,
 	.read_status	= ksz886x_read_status,
 	.suspend	= genphy_suspend,
 	.resume		= ksz886x_resume,
+	.cable_test_start	= ksz886x_cable_test_start,
+	.cable_test_get_status	= ksz886x_cable_test_get_status,
 }, {
 	.name		= "Micrel KSZ87XX Switch",
 	/* PHY_BASIC_FEATURES */
-- 
2.29.2