netdev - Re: [PATCH v6 net-next 14/17] net: enetc: move sync packet modification before dma_map

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Message-ID: <aK8a3+gA52I6Ffcy@lizhi-Precision-Tower-5810>
Date: Wed, 27 Aug 2025 10:49:03 -0400
From: Frank Li <Frank.li@....com>
To: Wei Fang <wei.fang@....com>
Cc: robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org,
	richardcochran@...il.com, claudiu.manoil@....com,
	vladimir.oltean@....com, xiaoning.wang@....com,
	andrew+netdev@...n.ch, davem@...emloft.net, edumazet@...gle.com,
	kuba@...nel.org, pabeni@...hat.com, vadim.fedorenko@...ux.dev,
	shawnguo@...nel.org, fushi.peng@....com, devicetree@...r.kernel.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	imx@...ts.linux.dev
Subject: Re: [PATCH v6 net-next 14/17] net: enetc: move sync packet
 modification before dma_map_single()

On Wed, Aug 27, 2025 at 02:33:29PM +0800, Wei Fang wrote:
> Move sync packet content modification before dma_map_single() to follow
> correct DMA usage process, even though the previous sequence worked due
> to hardware DMA-coherence support (LS1028A). But for the upcoming i.MX95,
> its ENETC (v4) does not support "dma-coherent", so this step is very
> necessary. Otherwise, the originTimestamp and correction fields of the
> sent packets will still be the values before the modification.
>
> Signed-off-by: Wei Fang <wei.fang@....com>

Reviewed-by: Frank Li <Frank.Li@....com>

>
> ---
> v6 changes:
> new patch, separated from the patch "net: enetc: add PTP synchronization
> support for ENETC v4"
> ---
>  drivers/net/ethernet/freescale/enetc/enetc.c | 15 ++++++++-------
>  1 file changed, 8 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/net/ethernet/freescale/enetc/enetc.c b/drivers/net/ethernet/freescale/enetc/enetc.c
> index 4325eb3d9481..25379ac7d69d 100644
> --- a/drivers/net/ethernet/freescale/enetc/enetc.c
> +++ b/drivers/net/ethernet/freescale/enetc/enetc.c
> @@ -303,6 +303,7 @@ static int enetc_map_tx_buffs(struct enetc_bdr *tx_ring, struct sk_buff *skb)
>  	unsigned int f;
>  	dma_addr_t dma;
>  	u8 flags = 0;
> +	u32 tstamp;
>
>  	enetc_clear_tx_bd(&temp_bd);
>  	if (skb->ip_summed == CHECKSUM_PARTIAL) {
> @@ -327,6 +328,13 @@ static int enetc_map_tx_buffs(struct enetc_bdr *tx_ring, struct sk_buff *skb)
>  		}
>  	}
>
> +	if (enetc_cb->flag & ENETC_F_TX_ONESTEP_SYNC_TSTAMP) {
> +		do_onestep_tstamp = true;
> +		tstamp = enetc_update_ptp_sync_msg(priv, skb);
> +	} else if (enetc_cb->flag & ENETC_F_TX_TSTAMP) {
> +		do_twostep_tstamp = true;
> +	}
> +
>  	i = tx_ring->next_to_use;
>  	txbd = ENETC_TXBD(*tx_ring, i);
>  	prefetchw(txbd);
> @@ -346,11 +354,6 @@ static int enetc_map_tx_buffs(struct enetc_bdr *tx_ring, struct sk_buff *skb)
>  	count++;
>
>  	do_vlan = skb_vlan_tag_present(skb);
> -	if (enetc_cb->flag & ENETC_F_TX_ONESTEP_SYNC_TSTAMP)
> -		do_onestep_tstamp = true;
> -	else if (enetc_cb->flag & ENETC_F_TX_TSTAMP)
> -		do_twostep_tstamp = true;
> -
>  	tx_swbd->do_twostep_tstamp = do_twostep_tstamp;
>  	tx_swbd->qbv_en = !!(priv->active_offloads & ENETC_F_QBV);
>  	tx_swbd->check_wb = tx_swbd->do_twostep_tstamp || tx_swbd->qbv_en;
> @@ -393,8 +396,6 @@ static int enetc_map_tx_buffs(struct enetc_bdr *tx_ring, struct sk_buff *skb)
>  		}
>
>  		if (do_onestep_tstamp) {
> -			u32 tstamp = enetc_update_ptp_sync_msg(priv, skb);
> -
>  			/* Configure extension BD */
>  			temp_bd.ext.tstamp = cpu_to_le32(tstamp);
>  			e_flags |= ENETC_TXBD_E_FLAGS_ONE_STEP_PTP;
> --
> 2.34.1
>