net: phy: aquantia: add downshift support

Aquantia PHY's of the AQR107 family support the downshift feature.
Add support for it as standard PHY tunable so that it can be controlled
via ethtool.
The AQCS109 supports a proprietary 2-pair 1Gbps mode. If two such PHY's
are connected to each other with a 2-pair cable, they may not be able
to establish a link if both advertise modes > 1Gbps.

v2:
- add downshift event detection
- warn if downshift occurred
- read downshifted rate from vendor register
- enable downshift per default on all AQR107 family members
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/aquantia_main.c

@@ -33,17 +33,23 @@
 #define MDIO_AN_VEND_PROV			0xc400
 #define MDIO_AN_VEND_PROV_1000BASET_FULL	BIT(15)
 #define MDIO_AN_VEND_PROV_1000BASET_HALF	BIT(14)
+#define MDIO_AN_VEND_PROV_DOWNSHIFT_EN		BIT(4)
+#define MDIO_AN_VEND_PROV_DOWNSHIFT_MASK	GENMASK(3, 0)
+#define MDIO_AN_VEND_PROV_DOWNSHIFT_DFLT	4
 
 #define MDIO_AN_TX_VEND_STATUS1			0xc800
-#define MDIO_AN_TX_VEND_STATUS1_10BASET		(0x0 << 1)
-#define MDIO_AN_TX_VEND_STATUS1_100BASETX	(0x1 << 1)
-#define MDIO_AN_TX_VEND_STATUS1_1000BASET	(0x2 << 1)
-#define MDIO_AN_TX_VEND_STATUS1_10GBASET	(0x3 << 1)
-#define MDIO_AN_TX_VEND_STATUS1_2500BASET	(0x4 << 1)
-#define MDIO_AN_TX_VEND_STATUS1_5000BASET	(0x5 << 1)
-#define MDIO_AN_TX_VEND_STATUS1_RATE_MASK	(0x7 << 1)
+#define MDIO_AN_TX_VEND_STATUS1_RATE_MASK	GENMASK(3, 1)
+#define MDIO_AN_TX_VEND_STATUS1_10BASET		0
+#define MDIO_AN_TX_VEND_STATUS1_100BASETX	1
+#define MDIO_AN_TX_VEND_STATUS1_1000BASET	2
+#define MDIO_AN_TX_VEND_STATUS1_10GBASET	3
+#define MDIO_AN_TX_VEND_STATUS1_2500BASET	4
+#define MDIO_AN_TX_VEND_STATUS1_5000BASET	5
 #define MDIO_AN_TX_VEND_STATUS1_FULL_DUPLEX	BIT(0)
 
+#define MDIO_AN_TX_VEND_INT_STATUS1		0xcc00
+#define MDIO_AN_TX_VEND_INT_STATUS1_DOWNSHIFT	BIT(1)
+
 #define MDIO_AN_TX_VEND_INT_STATUS2		0xcc01
 
 #define MDIO_AN_TX_VEND_INT_MASK2		0xd401
@@ -186,6 +192,57 @@ static int aqr_read_status(struct phy_device *phydev)
 	return genphy_c45_read_status(phydev);
 }
 
+static int aqr107_read_downshift_event(struct phy_device *phydev)
+{
+	int val;
+
+	val = phy_read_mmd(phydev, MDIO_MMD_AN, MDIO_AN_TX_VEND_INT_STATUS1);
+	if (val < 0)
+		return val;
+
+	return !!(val & MDIO_AN_TX_VEND_INT_STATUS1_DOWNSHIFT);
+}
+
+static int aqr107_read_rate(struct phy_device *phydev)
+{
+	int val;
+
+	val = phy_read_mmd(phydev, MDIO_MMD_AN, MDIO_AN_TX_VEND_STATUS1);
+	if (val < 0)
+		return val;
+
+	switch (FIELD_GET(MDIO_AN_TX_VEND_STATUS1_RATE_MASK, val)) {
+	case MDIO_AN_TX_VEND_STATUS1_10BASET:
+		phydev->speed = SPEED_10;
+		break;
+	case MDIO_AN_TX_VEND_STATUS1_100BASETX:
+		phydev->speed = SPEED_100;
+		break;
+	case MDIO_AN_TX_VEND_STATUS1_1000BASET:
+		phydev->speed = SPEED_1000;
+		break;
+	case MDIO_AN_TX_VEND_STATUS1_2500BASET:
+		phydev->speed = SPEED_2500;
+		break;
+	case MDIO_AN_TX_VEND_STATUS1_5000BASET:
+		phydev->speed = SPEED_5000;
+		break;
+	case MDIO_AN_TX_VEND_STATUS1_10GBASET:
+		phydev->speed = SPEED_10000;
+		break;
+	default:
+		phydev->speed = SPEED_UNKNOWN;
+		break;
+	}
+
+	if (val & MDIO_AN_TX_VEND_STATUS1_FULL_DUPLEX)
+		phydev->duplex = DUPLEX_FULL;
+	else
+		phydev->duplex = DUPLEX_HALF;
+
+	return 0;
+}
+
 static int aqr107_read_status(struct phy_device *phydev)
 {
 	int val, ret;
@@ -194,7 +251,7 @@ static int aqr107_read_status(struct phy_device *phydev)
 	if (ret)
 		return ret;
 
-	if (!phydev->link)
+	if (!phydev->link || phydev->autoneg == AUTONEG_DISABLE)
 		return 0;
 
 	val = phy_read_mmd(phydev, MDIO_MMD_PHYXS, MDIO_PHYXS_VEND_IF_STATUS);
@@ -217,9 +274,71 @@ static int aqr107_read_status(struct phy_device *phydev)
 		break;
 	}
 
+	val = aqr107_read_downshift_event(phydev);
+	if (val <= 0)
+		return val;
+
+	phydev_warn(phydev, "Downshift occurred! Cabling may be defective.\n");
+
+	/* Read downshifted rate from vendor register */
+	return aqr107_read_rate(phydev);
+}
+
+static int aqr107_get_downshift(struct phy_device *phydev, u8 *data)
+{
+	int val, cnt, enable;
+
+	val = phy_read_mmd(phydev, MDIO_MMD_AN, MDIO_AN_VEND_PROV);
+	if (val < 0)
+		return val;
+
+	enable = FIELD_GET(MDIO_AN_VEND_PROV_DOWNSHIFT_EN, val);
+	cnt = FIELD_GET(MDIO_AN_VEND_PROV_DOWNSHIFT_MASK, val);
+
+	*data = enable && cnt ? cnt : DOWNSHIFT_DEV_DISABLE;
+
 	return 0;
 }
 
+static int aqr107_set_downshift(struct phy_device *phydev, u8 cnt)
+{
+	int val = 0;
+
+	if (!FIELD_FIT(MDIO_AN_VEND_PROV_DOWNSHIFT_MASK, cnt))
+		return -E2BIG;
+
+	if (cnt != DOWNSHIFT_DEV_DISABLE) {
+		val = MDIO_AN_VEND_PROV_DOWNSHIFT_EN;
+		val |= FIELD_PREP(MDIO_AN_VEND_PROV_DOWNSHIFT_MASK, cnt);
+	}
+
+	return phy_modify_mmd(phydev, MDIO_MMD_AN, MDIO_AN_VEND_PROV,
+			      MDIO_AN_VEND_PROV_DOWNSHIFT_EN |
+			      MDIO_AN_VEND_PROV_DOWNSHIFT_MASK, val);
+}
+
+static int aqr107_get_tunable(struct phy_device *phydev,
+			      struct ethtool_tunable *tuna, void *data)
+{
+	switch (tuna->id) {
+	case ETHTOOL_PHY_DOWNSHIFT:
+		return aqr107_get_downshift(phydev, data);
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+
+static int aqr107_set_tunable(struct phy_device *phydev,
+			      struct ethtool_tunable *tuna, const void *data)
+{
+	switch (tuna->id) {
+	case ETHTOOL_PHY_DOWNSHIFT:
+		return aqr107_set_downshift(phydev, *(const u8 *)data);
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+
 static int aqr107_config_init(struct phy_device *phydev)
 {
 	/* Check that the PHY interface type is compatible */
@@ -228,11 +347,16 @@ static int aqr107_config_init(struct phy_device *phydev)
 	    phydev->interface != PHY_INTERFACE_MODE_10GKR)
 		return -ENODEV;
 
-	return 0;
+	/* ensure that a latched downshift event is cleared */
+	aqr107_read_downshift_event(phydev);
+
+	return aqr107_set_downshift(phydev, MDIO_AN_VEND_PROV_DOWNSHIFT_DFLT);
 }
 
 static int aqcs109_config_init(struct phy_device *phydev)
 {
+	int ret;
+
 	/* Check that the PHY interface type is compatible */
 	if (phydev->interface != PHY_INTERFACE_MODE_SGMII &&
 	    phydev->interface != PHY_INTERFACE_MODE_2500BASEX)
@@ -242,7 +366,14 @@ static int aqcs109_config_init(struct phy_device *phydev)
 	 * PMA speed ability bits are the same for all members of the family,
 	 * AQCS109 however supports speeds up to 2.5G only.
 	 */
-	return phy_set_max_speed(phydev, SPEED_2500);
+	ret = phy_set_max_speed(phydev, SPEED_2500);
+	if (ret)
+		return ret;
+
+	/* ensure that a latched downshift event is cleared */
+	aqr107_read_downshift_event(phydev);
+
+	return aqr107_set_downshift(phydev, MDIO_AN_VEND_PROV_DOWNSHIFT_DFLT);
 }
 
 static struct phy_driver aqr_driver[] = {
@@ -297,6 +428,8 @@ static struct phy_driver aqr_driver[] = {
 	.config_intr	= aqr_config_intr,
 	.ack_interrupt	= aqr_ack_interrupt,
 	.read_status	= aqr107_read_status,
+	.get_tunable    = aqr107_get_tunable,
+	.set_tunable    = aqr107_set_tunable,
 },
 {
 	PHY_ID_MATCH_MODEL(PHY_ID_AQCS109),
@@ -309,6 +442,8 @@ static struct phy_driver aqr_driver[] = {
 	.config_intr	= aqr_config_intr,
 	.ack_interrupt	= aqr_ack_interrupt,
 	.read_status	= aqr107_read_status,
+	.get_tunable    = aqr107_get_tunable,
+	.set_tunable    = aqr107_set_tunable,
 },
 {
 	PHY_ID_MATCH_MODEL(PHY_ID_AQR405),