[PATCH net-next 2/2] net: phy: marvell: add PHY tunable fast link down support for 88E1540

[Heiner Kallweit <hkallweit1@gmail.com>]

1000BaseT standard requires that a link is reported as down earliest
after 750ms. Several use case however require a much faster detecion
of a broken link. Fast Link Down supports this by intentionally
violating a the standard. This patch exposes the Fast Link Down
feature of 88E1540 and 88E6390. These PHY's can be found as internal
PHY's in several switches: 88E6352, 88E6240, 88E6176, 88E6172,
and 88E6390(X). Fast Link Down and EEE are mutually exclusive.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
---
 drivers/net/phy/marvell.c | 108 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 108 insertions(+)

diff --git a/drivers/net/phy/marvell.c b/drivers/net/phy/marvell.c
index 3ccba37bd..65350186d 100644
--- a/drivers/net/phy/marvell.c
+++ b/drivers/net/phy/marvell.c
@@ -29,6 +29,7 @@
 #include <linux/ethtool.h>
 #include <linux/phy.h>
 #include <linux/marvell_phy.h>
+#include <linux/bitfield.h>
 #include <linux/of.h>
 
 #include <linux/io.h>
@@ -91,6 +92,14 @@
 #define MII_88E1510_TEMP_SENSOR		0x1b
 #define MII_88E1510_TEMP_SENSOR_MASK	0xff
 
+#define MII_88E1540_COPPER_CTRL3	0x1a
+#define MII_88E1540_COPPER_CTRL3_LINK_DOWN_DELAY_MASK	GENMASK(11, 10)
+#define MII_88E1540_COPPER_CTRL3_LINK_DOWN_DELAY_00MS	0
+#define MII_88E1540_COPPER_CTRL3_LINK_DOWN_DELAY_10MS	1
+#define MII_88E1540_COPPER_CTRL3_LINK_DOWN_DELAY_20MS	2
+#define MII_88E1540_COPPER_CTRL3_LINK_DOWN_DELAY_40MS	3
+#define MII_88E1540_COPPER_CTRL3_FAST_LINK_DOWN		BIT(9)
+
 #define MII_88E6390_MISC_TEST		0x1b
 #define MII_88E6390_MISC_TEST_SAMPLE_1S		0
 #define MII_88E6390_MISC_TEST_SAMPLE_10MS	BIT(14)
@@ -1025,6 +1034,101 @@ static int m88e1145_config_init(struct phy_device *phydev)
 	return 0;
 }
 
+static int m88e1540_get_fld(struct phy_device *phydev, u8 *msecs)
+{
+	int val;
+
+	val = phy_read(phydev, MII_88E1540_COPPER_CTRL3);
+	if (val < 0)
+		return val;
+
+	if (!(val & MII_88E1540_COPPER_CTRL3_FAST_LINK_DOWN)) {
+		*msecs = ETHTOOL_PHY_FAST_LINK_DOWN_OFF;
+		return 0;
+	}
+
+	val = FIELD_GET(MII_88E1540_COPPER_CTRL3_LINK_DOWN_DELAY_MASK, val);
+
+	switch (val) {
+	case MII_88E1540_COPPER_CTRL3_LINK_DOWN_DELAY_00MS:
+		*msecs = 0;
+		break;
+	case MII_88E1540_COPPER_CTRL3_LINK_DOWN_DELAY_10MS:
+		*msecs = 10;
+		break;
+	case MII_88E1540_COPPER_CTRL3_LINK_DOWN_DELAY_20MS:
+		*msecs = 20;
+		break;
+	case MII_88E1540_COPPER_CTRL3_LINK_DOWN_DELAY_40MS:
+		*msecs = 40;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int m88e1540_set_fld(struct phy_device *phydev, const u8 *msecs)
+{
+	struct ethtool_eee eee;
+	int val, ret;
+
+	if (*msecs == ETHTOOL_PHY_FAST_LINK_DOWN_OFF)
+		return phy_clear_bits(phydev, MII_88E1540_COPPER_CTRL3,
+				      MII_88E1540_COPPER_CTRL3_FAST_LINK_DOWN);
+
+	/* According to the Marvell data sheet EEE must be disabled for
+	 * Fast Link Down detection to work properly
+	 */
+	ret = phy_ethtool_get_eee(phydev, &eee);
+	if (!ret && eee.eee_enabled) {
+		phydev_warn(phydev, "Fast Link Down detection requires EEE to be disabled!\n");
+		return -EBUSY;
+	}
+
+	if (*msecs <= 5)
+		val = MII_88E1540_COPPER_CTRL3_LINK_DOWN_DELAY_00MS;
+	else if (*msecs <= 15)
+		val = MII_88E1540_COPPER_CTRL3_LINK_DOWN_DELAY_10MS;
+	else if (*msecs <= 30)
+		val = MII_88E1540_COPPER_CTRL3_LINK_DOWN_DELAY_20MS;
+	else
+		val = MII_88E1540_COPPER_CTRL3_LINK_DOWN_DELAY_40MS;
+
+	val = FIELD_PREP(MII_88E1540_COPPER_CTRL3_LINK_DOWN_DELAY_MASK, val);
+
+	ret = phy_modify(phydev, MII_88E1540_COPPER_CTRL3,
+			 MII_88E1540_COPPER_CTRL3_LINK_DOWN_DELAY_MASK, val);
+	if (ret)
+		return ret;
+
+	return phy_set_bits(phydev, MII_88E1540_COPPER_CTRL3,
+			    MII_88E1540_COPPER_CTRL3_FAST_LINK_DOWN);
+}
+
+static int m88e1540_get_tunable(struct phy_device *phydev,
+				struct ethtool_tunable *tuna, void *data)
+{
+	switch (tuna->id) {
+	case ETHTOOL_PHY_FAST_LINK_DOWN:
+		return m88e1540_get_fld(phydev, data);
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+
+static int m88e1540_set_tunable(struct phy_device *phydev,
+				struct ethtool_tunable *tuna, const void *data)
+{
+	switch (tuna->id) {
+	case ETHTOOL_PHY_FAST_LINK_DOWN:
+		return m88e1540_set_fld(phydev, data);
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+
 /* The VOD can be out of specification on link up. Poke an
  * undocumented register, in an undocumented page, with a magic value
  * to fix this.
@@ -2247,6 +2351,8 @@ static struct phy_driver marvell_drivers[] = {
 		.get_sset_count = marvell_get_sset_count,
 		.get_strings = marvell_get_strings,
 		.get_stats = marvell_get_stats,
+		.get_tunable = m88e1540_get_tunable,
+		.set_tunable = m88e1540_set_tunable,
 	},
 	{
 		.phy_id = MARVELL_PHY_ID_88E1545,
@@ -2307,6 +2413,8 @@ static struct phy_driver marvell_drivers[] = {
 		.get_sset_count = marvell_get_sset_count,
 		.get_strings = marvell_get_strings,
 		.get_stats = marvell_get_stats,
+		.get_tunable = m88e1540_get_tunable,
+		.set_tunable = m88e1540_set_tunable,
 	},
 };
 
-- 
2.21.0