linux-kernel - Re: [PATCH net-next v2] net/mlx5: support software TX timestamp

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Message-ID: <CAL+tcoCwAUNmBuN1KR5oa90nZGMqOeNc-xEYdi2nairE5-1BBw@mail.gmail.com>
Date: Fri, 9 May 2025 11:50:04 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Stanislav Fomichev <stfomichev@...il.com>
Cc: netdev@...r.kernel.org, davem@...emloft.net, edumazet@...gle.com, 
	kuba@...nel.org, pabeni@...hat.com, saeedm@...dia.com, tariqt@...dia.com, 
	andrew+netdev@...n.ch, linux-rdma@...r.kernel.org, 
	linux-kernel@...r.kernel.org, leon@...nel.org
Subject: Re: [PATCH net-next v2] net/mlx5: support software TX timestamp

On Fri, May 9, 2025 at 7:51 AM Stanislav Fomichev <stfomichev@...il.com> wrote:
>
> Having a software timestamp (along with existing hardware one) is
> useful to trace how the packets flow through the stack.
> mlx5e_tx_skb_update_hwts_flags is called from tx paths
> to setup HW timestamp; extend it to add software one as well.
>
> Reviewed-by: Jason Xing <kerneljasonxing@...il.com>
> Signed-off-by: Stanislav Fomichev <stfomichev@...il.com>

Thanks for working on this.

An a bit irrelevant topic here is it seems we miss adding
SOF_TIMESTAMPING_TX_SOFTWARE in mlx4_en_get_ts_info() since mlx4 has
used skb_tx_timestamp function in mlx4_en_xmit(). IIUC, I'm going to
send a patch to add this flag.

Thanks,
Jason

> ---
> v2: rename mlx5e_tx_skb_update_hwts_flags (Tariq & Jason)
> ---
>  drivers/net/ethernet/mellanox/mlx5/core/en_ethtool.c | 1 +
>  drivers/net/ethernet/mellanox/mlx5/core/en_tx.c      | 7 ++++---
>  2 files changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_ethtool.c b/drivers/net/ethernet/mellanox/mlx5/core/en_ethtool.c
> index fdf9e9bb99ac..e399d7a3d6cb 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/en_ethtool.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_ethtool.c
> @@ -1689,6 +1689,7 @@ int mlx5e_ethtool_get_ts_info(struct mlx5e_priv *priv,
>                 return 0;
>
>         info->so_timestamping = SOF_TIMESTAMPING_TX_HARDWARE |
> +                               SOF_TIMESTAMPING_TX_SOFTWARE |
>                                 SOF_TIMESTAMPING_RX_HARDWARE |
>                                 SOF_TIMESTAMPING_RAW_HARDWARE;
>
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c
> index 4fd853d19e31..55a8629f0792 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c
> @@ -337,10 +337,11 @@ static void mlx5e_sq_calc_wqe_attr(struct sk_buff *skb, const struct mlx5e_tx_at
>         };
>  }
>
> -static void mlx5e_tx_skb_update_hwts_flags(struct sk_buff *skb)
> +static void mlx5e_tx_skb_update_ts_flags(struct sk_buff *skb)
>  {
>         if (unlikely(skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP))
>                 skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS;
> +       skb_tx_timestamp(skb);
>  }
>
>  static void mlx5e_tx_check_stop(struct mlx5e_txqsq *sq)
> @@ -392,7 +393,7 @@ mlx5e_txwqe_complete(struct mlx5e_txqsq *sq, struct sk_buff *skb,
>         cseg->opmod_idx_opcode = cpu_to_be32((sq->pc << 8) | attr->opcode);
>         cseg->qpn_ds           = cpu_to_be32((sq->sqn << 8) | wqe_attr->ds_cnt);
>
> -       mlx5e_tx_skb_update_hwts_flags(skb);
> +       mlx5e_tx_skb_update_ts_flags(skb);
>
>         sq->pc += wi->num_wqebbs;
>
> @@ -625,7 +626,7 @@ mlx5e_sq_xmit_mpwqe(struct mlx5e_txqsq *sq, struct sk_buff *skb,
>         mlx5e_dma_push(sq, txd.dma_addr, txd.len, MLX5E_DMA_MAP_SINGLE);
>         mlx5e_skb_fifo_push(&sq->db.skb_fifo, skb);
>         mlx5e_tx_mpwqe_add_dseg(sq, &txd);
> -       mlx5e_tx_skb_update_hwts_flags(skb);
> +       mlx5e_tx_skb_update_ts_flags(skb);
>
>         if (unlikely(mlx5e_tx_mpwqe_is_full(&sq->mpwqe))) {
>                 /* Might stop the queue and affect the retval of __netdev_tx_sent_queue. */
> --
> 2.49.0
>