ethtool: provide UAPI for PHY Signal Quality Index (SQI)

Signal Quality Index is a mandatory value required by "OPEN Alliance
SIG" for the 100Base-T1 PHYs [1]. This indicator can be used for cable
integrity diagnostic and investigating other noise sources and
implement by at least two vendors: NXP[2] and TI[3].

[1] http://www.opensig.org/download/document/218/Advanced_PHY_features_for_automotive_Ethernet_V1.0.pdf
[2] https://www.nxp.com/docs/en/data-sheet/TJA1100.pdf
[3] https://www.ti.com/product/DP83TC811R-Q1Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Michal Kubecek <mkubecek@suse.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/ethtool-netlink.rst

@@ -454,10 +454,12 @@ Request contents:
 
 Kernel response contents:
 
-  ====================================  ======  ==========================
+  ====================================  ======  ============================
   ``ETHTOOL_A_LINKSTATE_HEADER``        nested  reply header
   ``ETHTOOL_A_LINKSTATE_LINK``          bool    link state (up/down)
-  ====================================  ======  ==========================
+  ``ETHTOOL_A_LINKSTATE_SQI``           u32     Current Signal Quality Index
+  ``ETHTOOL_A_LINKSTATE_SQI_MAX``       u32     Max support SQI value
+  ====================================  ======  ============================
 
 For most NIC drivers, the value of ``ETHTOOL_A_LINKSTATE_LINK`` returns
 carrier flag provided by ``netif_carrier_ok()`` but there are drivers which

include/linux/phy.h

@@ -723,6 +723,8 @@ struct phy_driver {
 			    struct ethtool_tunable *tuna,
 			    const void *data);
 	int (*set_loopback)(struct phy_device *dev, bool enable);
+	int (*get_sqi)(struct phy_device *dev);
+	int (*get_sqi_max)(struct phy_device *dev);
 };
 #define to_phy_driver(d) container_of(to_mdio_common_driver(d),		\
 				      struct phy_driver, mdiodrv)

include/uapi/linux/ethtool_netlink.h

@@ -232,6 +232,8 @@ enum {
 	ETHTOOL_A_LINKSTATE_UNSPEC,
 	ETHTOOL_A_LINKSTATE_HEADER,		/* nest - _A_HEADER_* */
 	ETHTOOL_A_LINKSTATE_LINK,		/* u8 */
+	ETHTOOL_A_LINKSTATE_SQI,		/* u32 */
+	ETHTOOL_A_LINKSTATE_SQI_MAX,		/* u32 */
 
 	/* add new constants above here */
 	__ETHTOOL_A_LINKSTATE_CNT,

net/ethtool/linkstate.c

@@ -2,6 +2,7 @@
 
 #include "netlink.h"
 #include "common.h"
+#include <linux/phy.h>
 
 struct linkstate_req_info {
 	struct ethnl_req_info		base;
@@ -10,6 +11,8 @@ struct linkstate_req_info {
 struct linkstate_reply_data {
 	struct ethnl_reply_data		base;
 	int				link;
+	int				sqi;
+	int				sqi_max;
 };
 
 #define LINKSTATE_REPDATA(__reply_base) \
@@ -20,8 +23,46 @@ linkstate_get_policy[ETHTOOL_A_LINKSTATE_MAX + 1] = {
 	[ETHTOOL_A_LINKSTATE_UNSPEC]		= { .type = NLA_REJECT },
 	[ETHTOOL_A_LINKSTATE_HEADER]		= { .type = NLA_NESTED },
 	[ETHTOOL_A_LINKSTATE_LINK]		= { .type = NLA_REJECT },
+	[ETHTOOL_A_LINKSTATE_SQI]		= { .type = NLA_REJECT },
+	[ETHTOOL_A_LINKSTATE_SQI_MAX]		= { .type = NLA_REJECT },
 };
 
+static int linkstate_get_sqi(struct net_device *dev)
+{
+	struct phy_device *phydev = dev->phydev;
+	int ret;
+
+	if (!phydev)
+		return -EOPNOTSUPP;
+
+	mutex_lock(&phydev->lock);
+	if (!phydev->drv || !phydev->drv->get_sqi)
+		ret = -EOPNOTSUPP;
+	else
+		ret = phydev->drv->get_sqi(phydev);
+	mutex_unlock(&phydev->lock);
+
+	return ret;
+}
+
+static int linkstate_get_sqi_max(struct net_device *dev)
+{
+	struct phy_device *phydev = dev->phydev;
+	int ret;
+
+	if (!phydev)
+		return -EOPNOTSUPP;
+
+	mutex_lock(&phydev->lock);
+	if (!phydev->drv || !phydev->drv->get_sqi_max)
+		ret = -EOPNOTSUPP;
+	else
+		ret = phydev->drv->get_sqi_max(phydev);
+	mutex_unlock(&phydev->lock);
+
+	return ret;
+}
+
 static int linkstate_prepare_data(const struct ethnl_req_info *req_base,
 				  struct ethnl_reply_data *reply_base,
 				  struct genl_info *info)
@@ -34,6 +75,19 @@ static int linkstate_prepare_data(const struct ethnl_req_info *req_base,
 	if (ret < 0)
 		return ret;
 	data->link = __ethtool_get_link(dev);
+
+	ret = linkstate_get_sqi(dev);
+	if (ret < 0 && ret != -EOPNOTSUPP)
+		return ret;
+
+	data->sqi = ret;
+
+	ret = linkstate_get_sqi_max(dev);
+	if (ret < 0 && ret != -EOPNOTSUPP)
+		return ret;
+
+	data->sqi_max = ret;
+
 	ethnl_ops_complete(dev);
 
 	return 0;
@@ -42,8 +96,19 @@ static int linkstate_prepare_data(const struct ethnl_req_info *req_base,
 static int linkstate_reply_size(const struct ethnl_req_info *req_base,
 				const struct ethnl_reply_data *reply_base)
 {
-	return nla_total_size(sizeof(u8)) /* LINKSTATE_LINK */
+	struct linkstate_reply_data *data = LINKSTATE_REPDATA(reply_base);
+	int len;
+
+	len = nla_total_size(sizeof(u8)) /* LINKSTATE_LINK */
 		+ 0;
+
+	if (data->sqi != -EOPNOTSUPP)
+		len += nla_total_size(sizeof(u32));
+
+	if (data->sqi_max != -EOPNOTSUPP)
+		len += nla_total_size(sizeof(u32));
+
+	return len;
 }
 
 static int linkstate_fill_reply(struct sk_buff *skb,
@@ -56,6 +121,14 @@ static int linkstate_fill_reply(struct sk_buff *skb,
 	    nla_put_u8(skb, ETHTOOL_A_LINKSTATE_LINK, !!data->link))
 		return -EMSGSIZE;
 
+	if (data->sqi != -EOPNOTSUPP &&
+	    nla_put_u32(skb, ETHTOOL_A_LINKSTATE_SQI, data->sqi))
+		return -EMSGSIZE;
+
+	if (data->sqi_max != -EOPNOTSUPP &&
+	    nla_put_u32(skb, ETHTOOL_A_LINKSTATE_SQI_MAX, data->sqi_max))
+		return -EMSGSIZE;
+
 	return 0;
 }