Re: [PATCH net-next v1 4/4] net: stmmac: use delays reported by the PHY driver to correct MAC propagation delay

[Serge Semin]

On Wed, Apr 17, 2024 at 06:43:16PM +0200, Oleksij Rempel wrote:
> Now after PHY drivers are able to report data path delays, we can use
> them in the MAC drivers for the delay correction.
> 
> Signed-off-by: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>
> ---
>  drivers/net/ethernet/stmicro/stmmac/stmmac.h    |  2 ++
>  .../ethernet/stmicro/stmmac/stmmac_hwtstamp.c   |  4 ++++
>  .../net/ethernet/stmicro/stmmac/stmmac_main.c   | 17 ++++++++++++++++-
>  3 files changed, 22 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac.h b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
> index dddcaa9220cc3..6db54ce33ea72 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac.h
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
> @@ -288,6 +288,8 @@ struct stmmac_priv {
>  	u32 sub_second_inc;
>  	u32 systime_flags;
>  	u32 adv_ts;

> +	u64 phy_tx_delay_ns;
> +	u64 phy_rx_delay_ns;

What's the point in adding these fields to the private data if you
retrieve the delays and use them in a single place? Just extend the
stmmac_hwtstamp_correct_latency() arguments list and pass the delays
as the function parameters.

-Serge(y)

>  	int use_riwt;
>  	int irq_wake;
>  	rwlock_t ptp_lock;
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c
> index f05bd757dfe52..bbf284cb7cc2a 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c
> @@ -71,6 +71,8 @@ static void hwtstamp_correct_latency(struct stmmac_priv *priv)
>  	/* MAC-internal ingress latency */
>  	scaled_ns = readl(ioaddr + PTP_TS_INGR_LAT);
>  
> +	scaled_ns += priv->phy_rx_delay_ns << 16;
> +
>  	/* See section 11.7.2.5.3.1 "Ingress Correction" on page 4001 of
>  	 * i.MX8MP Applications Processor Reference Manual Rev. 1, 06/2021
>  	 */
> @@ -95,6 +97,8 @@ static void hwtstamp_correct_latency(struct stmmac_priv *priv)
>  	/* MAC-internal egress latency */
>  	scaled_ns = readl(ioaddr + PTP_TS_EGR_LAT);
>  
> +	scaled_ns += priv->phy_tx_delay_ns << 16;
> +
>  	reg_tsec = scaled_ns >> 16;
>  	reg_tsecsns = scaled_ns & 0xff00;
>  
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index fe3498e86de9d..30c7c278b7062 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -1097,8 +1097,23 @@ static void stmmac_mac_link_up(struct phylink_config *config,
>  	if (priv->dma_cap.fpesel)
>  		stmmac_fpe_link_state_handle(priv, true);
>  
> -	if (priv->plat->flags & STMMAC_FLAG_HWTSTAMP_CORRECT_LATENCY)
> +	if (priv->plat->flags & STMMAC_FLAG_HWTSTAMP_CORRECT_LATENCY) {
> +		int ret = 0;
> +
> +		if (phy)
> +			ret = phy_get_timesync_data_path_delays(phy,
> +								&priv->phy_tx_delay_ns,
> +								&priv->phy_rx_delay_ns);
> +		if (!phy || ret) {
> +			if (ret != -EOPNOTSUPP)
> +				netdev_err(priv->dev, "Failed to get PHY delay: %pe\n",
> +					   ERR_PTR(ret));
> +			priv->phy_tx_delay_ns = 0;
> +			priv->phy_rx_delay_ns = 0;
> +		}
> +
>  		stmmac_hwtstamp_correct_latency(priv, priv);
> +	}
>  }
>  
>  static const struct phylink_mac_ops stmmac_phylink_mac_ops = {
> -- 
> 2.39.2
> 
>