bonding: add software tx timestamping support

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>
Acked-by: Jay Vosburgh <jay.vosburgh@canonical.com>
Link: https://lore.kernel.org/r/20230418034841.2566262-1-liuhangbin@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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:

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