Re: [PATCH net-next] net: mvneta: add support for hardware timestamps

["Russell King (Oracle)" <linux@armlinux.org.uk>]

On Tue, Sep 09, 2025 at 04:30:01PM +0100, Russell King wrote:
> Add support for hardware timestamps in (e.g.) the PHY by calling
> skb_tx_timestamp() as close as reasonably possible to the point that
> the hardware is instructed to send the queued packets.
> 
> Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
> ---
>  drivers/net/ethernet/marvell/mvneta.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
> index 476e73e502fe..5f4e28085640 100644
> --- a/drivers/net/ethernet/marvell/mvneta.c
> +++ b/drivers/net/ethernet/marvell/mvneta.c
> @@ -2985,6 +2985,13 @@ static netdev_tx_t mvneta_tx(struct sk_buff *skb, struct net_device *dev)
>  		if (txq->count >= txq->tx_stop_threshold)
>  			netif_tx_stop_queue(nq);
>  
> +		/* FIXME: This is not really the true transmit point, since
> +		 * we batch up several before hitting the hardware, but is
> +		 * the best we can do without more complexity to walk the
> +		 * packets in the pending section of the transmit queue.
> +		 */
> +		skb_tx_timestamp(skb);
> +

A question to netdev timestamping people...

As I understand it, skb_tx_timestamp() not only adds support for
PHY-based hardware timestamping, but also adds software timestamping
at the point this call is made (hence why it needs to be placed
carefully.)

If a driver has skb_tx_timestmap() added, should the driver also
fill in the ethtool .get_ts_info() method, presumably with
ethtool_op_get_ts_info() ?

Thanks.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!