netdev - [PATCH net-next v2 1/2] ethtool: add PHY Fast Link Down support

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Date:   Mon, 25 Mar 2019 19:34:58 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        David Miller <davem@...emloft.net>,
        "John W. Linville" <linville@...driver.com>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: [PATCH net-next v2 1/2] ethtool: add PHY Fast Link Down support

This adds support for Fast Link Down as new PHY tunable.
Fast Link Down reduces the time until a link down event is reported
for 1000BaseT. According to the standard it's 750ms what is too long
for several use cases.

v2:
- add comment describing the constants

Signed-off-by: Heiner Kallweit <hkallweit1@...il.com>
---
 include/uapi/linux/ethtool.h | 8 ++++++++
 net/core/ethtool.c           | 2 ++
 2 files changed, 10 insertions(+)

diff --git a/include/uapi/linux/ethtool.h b/include/uapi/linux/ethtool.h
index 3652b239d..50c76f4fa 100644
--- a/include/uapi/linux/ethtool.h
+++ b/include/uapi/linux/ethtool.h
@@ -252,9 +252,17 @@ struct ethtool_tunable {
 #define DOWNSHIFT_DEV_DEFAULT_COUNT	0xff
 #define DOWNSHIFT_DEV_DISABLE		0
 
+/* Time in msecs after which link is reported as down
+ * 0 = lowest time supported by the PHY
+ * 0xff = off, link down detection according to standard
+ */
+#define ETHTOOL_PHY_FAST_LINK_DOWN_ON	0
+#define ETHTOOL_PHY_FAST_LINK_DOWN_OFF	0xff
+
 enum phy_tunable_id {
 	ETHTOOL_PHY_ID_UNSPEC,
 	ETHTOOL_PHY_DOWNSHIFT,
+	ETHTOOL_PHY_FAST_LINK_DOWN,
 	/*
 	 * Add your fresh new phy tunable attribute above and remember to update
 	 * phy_tunable_strings[] in net/core/ethtool.c
diff --git a/net/core/ethtool.c b/net/core/ethtool.c
index b1eb32419..387d67eb7 100644
--- a/net/core/ethtool.c
+++ b/net/core/ethtool.c
@@ -136,6 +136,7 @@ static const char
 phy_tunable_strings[__ETHTOOL_PHY_TUNABLE_COUNT][ETH_GSTRING_LEN] = {
 	[ETHTOOL_ID_UNSPEC]     = "Unspec",
 	[ETHTOOL_PHY_DOWNSHIFT]	= "phy-downshift",
+	[ETHTOOL_PHY_FAST_LINK_DOWN] = "phy-fast-link-down",
 };
 
 static int ethtool_get_features(struct net_device *dev, void __user *useraddr)
@@ -2432,6 +2433,7 @@ static int ethtool_phy_tunable_valid(const struct ethtool_tunable *tuna)
 {
 	switch (tuna->id) {
 	case ETHTOOL_PHY_DOWNSHIFT:
+	case ETHTOOL_PHY_FAST_LINK_DOWN:
 		if (tuna->len != sizeof(u8) ||
 		    tuna->type_id != ETHTOOL_TUNABLE_U8)
 			return -EINVAL;
-- 
2.21.0