[PATCHv5 net-next] bonding: add software tx timestamping support

[Hangbin Liu <liuhangbin@gmail.com>]

Currently, bonding only obtain the timestamp (ts) information of
the active slave, which is available only for modes 1, 5, and 6.
For other modes, bonding only has software rx timestamping support.

However, some users who use modes such as LACP also want tx timestamp
support. To address this issue, let's check the ts information of each
slave. If all slaves support tx timestamping, we can enable tx
timestamping support for the bond.

Add a note that the get_ts_info may be called with RCU, or rtnl or
reference on the device in ethtool.h>

Suggested-by: Miroslav Lichvar <mlichvar@redhat.com>
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
---
v5: remove ASSERT_RTNL since bond_ethtool_get_ts_info could be called
    without RTNL. Update ethtool kdoc.
v4: add ASSERT_RTNL to make sure bond_ethtool_get_ts_info() called via
    RTNL. Only check _TX_SOFTWARE for the slaves.
v3: remove dev_hold/dev_put. remove the '\' for line continuation.
v2: check each slave's ts info to make sure bond support sw tx
    timestamping
---
 drivers/net/bonding/bond_main.c | 30 ++++++++++++++++++++++++++++++
 include/linux/ethtool.h         |  1 +
 2 files changed, 31 insertions(+)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 8cc9a74789b7..db7e650d9ebb 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -5696,9 +5696,13 @@ static int bond_ethtool_get_ts_info(struct net_device *bond_dev,
 				    struct ethtool_ts_info *info)
 {
 	struct bonding *bond = netdev_priv(bond_dev);
+	struct ethtool_ts_info ts_info;
 	const struct ethtool_ops *ops;
 	struct net_device *real_dev;
+	bool sw_tx_support = false;
 	struct phy_device *phydev;
+	struct list_head *iter;
+	struct slave *slave;
 	int ret = 0;
 
 	rcu_read_lock();
@@ -5717,10 +5721,36 @@ static int bond_ethtool_get_ts_info(struct net_device *bond_dev,
 			ret = ops->get_ts_info(real_dev, info);
 			goto out;
 		}
+	} else {
+		/* Check if all slaves support software tx timestamping */
+		rcu_read_lock();
+		bond_for_each_slave_rcu(bond, slave, iter) {
+			ret = -1;
+			ops = slave->dev->ethtool_ops;
+			phydev = slave->dev->phydev;
+
+			if (phy_has_tsinfo(phydev))
+				ret = phy_ts_info(phydev, &ts_info);
+			else if (ops->get_ts_info)
+				ret = ops->get_ts_info(slave->dev, &ts_info);
+
+			if (!ret && (ts_info.so_timestamping & SOF_TIMESTAMPING_TX_SOFTWARE)) {
+				sw_tx_support = true;
+				continue;
+			}
+
+			sw_tx_support = false;
+			break;
+		}
+		rcu_read_unlock();
 	}
 
+	ret = 0;
 	info->so_timestamping = SOF_TIMESTAMPING_RX_SOFTWARE |
 				SOF_TIMESTAMPING_SOFTWARE;
+	if (sw_tx_support)
+		info->so_timestamping |= SOF_TIMESTAMPING_TX_SOFTWARE;
+
 	info->phc_index = -1;
 
 out:
diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
index 798d35890118..62b61527bcc4 100644
--- a/include/linux/ethtool.h
+++ b/include/linux/ethtool.h
@@ -711,6 +711,7 @@ struct ethtool_mm_stats {
  * @get_dump_data: Get dump data.
  * @set_dump: Set dump specific flags to the device.
  * @get_ts_info: Get the time stamping and PTP hardware clock capabilities.
+ *	It may be called with RCU, or rtnl or reference on the device.
  *	Drivers supporting transmit time stamps in software should set this to
  *	ethtool_op_get_ts_info().
  * @get_module_info: Get the size and type of the eeprom contained within
-- 
2.38.1