netdev - Re: [PATCH net-next v3 3/4] net: stmmac: add Rx HWTS metadata to XDP receive pkt

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Message-ID: <ZDbjkwGS5L9wdS5h@google.com>
Date:   Wed, 12 Apr 2023 10:00:03 -0700
From:   Stanislav Fomichev <sdf@...gle.com>
To:     Song Yoong Siang <yoong.siang.song@...el.com>
Cc:     Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Jose Abreu <joabreu@...opsys.com>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Alexander Duyck <alexanderduyck@...com>,
        Ong Boon Leong <boon.leong.ong@...el.com>,
        netdev@...r.kernel.org, linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        bpf@...r.kernel.org, xdp-hints@...-project.net
Subject: Re: [PATCH net-next v3 3/4] net: stmmac: add Rx HWTS metadata to XDP
 receive pkt

On 04/12, Song Yoong Siang wrote:
> Add receive hardware timestamp metadata support via kfunc to XDP receive
> packets.
> 
> Suggested-by: Stanislav Fomichev <sdf@...gle.com>
> Signed-off-by: Song Yoong Siang <yoong.siang.song@...el.com>
> ---
>  drivers/net/ethernet/stmicro/stmmac/stmmac.h  |  3 +++
>  .../net/ethernet/stmicro/stmmac/stmmac_main.c | 26 ++++++++++++++++++-
>  2 files changed, 28 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac.h b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
> index ac8ccf851708..826ac0ec88c6 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac.h
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
> @@ -94,6 +94,9 @@ struct stmmac_rx_buffer {
>  
>  struct stmmac_xdp_buff {
>  	struct xdp_buff xdp;
> +	struct stmmac_priv *priv;
> +	struct dma_desc *p;
> +	struct dma_desc *np;
>  };
>  
>  struct stmmac_rx_queue {
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index f7bbdf04d20c..ed660927b628 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -5315,10 +5315,15 @@ static int stmmac_rx(struct stmmac_priv *priv, int limit, u32 queue)
>  
>  			xdp_init_buff(&ctx.xdp, buf_sz, &rx_q->xdp_rxq);
>  			xdp_prepare_buff(&ctx.xdp, page_address(buf->page),
> -					 buf->page_offset, buf1_len, false);
> +					 buf->page_offset, buf1_len, true);
>  
>  			pre_len = ctx.xdp.data_end - ctx.xdp.data_hard_start -
>  				  buf->page_offset;
> +
> +			ctx.priv = priv;
> +			ctx.p = p;
> +			ctx.np = np;
> +
>  			skb = stmmac_xdp_run_prog(priv, &ctx.xdp);
>  			/* Due xdp_adjust_tail: DMA sync for_device
>  			 * cover max len CPU touch
> @@ -7071,6 +7076,23 @@ void stmmac_fpe_handshake(struct stmmac_priv *priv, bool enable)
>  	}
>  }
>  
> +static int stmmac_xdp_rx_timestamp(const struct xdp_md *_ctx, u64 *timestamp)
> +{
> +	const struct stmmac_xdp_buff *ctx = (void *)_ctx;
> +
> +	*timestamp = 0;
> +	stmmac_get_rx_hwtstamp(ctx->priv, ctx->p, ctx->np, timestamp);
> +

[..]

> +	if (*timestamp)

Nit: does it make sense to change stmmac_get_rx_hwtstamp to return bool
to indicate success/failure? Then you can do:

if (!stmmac_get_rx_hwtstamp())
	reutrn -ENODATA;