linux-kernel - Re: [PATCH bpf-next v2 2/3] net: stmmac: Add txtime support to XDP ZC

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Message-ID: <5a660c0f-d3ed-47a2-b9be-098a224b8a12@kernel.org>
Date:   Fri, 1 Dec 2023 16:02:22 +0100
From:   Jesper Dangaard Brouer <hawk@...nel.org>
To:     Song Yoong Siang <yoong.siang.song@...el.com>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Bjorn Topel <bjorn@...nel.org>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        John Fastabend <john.fastabend@...il.com>,
        Stanislav Fomichev <sdf@...gle.com>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Tariq Toukan <tariqt@...dia.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Mykola Lysenko <mykolal@...com>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>,
        Yonghong Song <yonghong.song@...ux.dev>,
        KP Singh <kpsingh@...nel.org>, Hao Luo <haoluo@...gle.com>,
        Jiri Olsa <jolsa@...nel.org>, Shuah Khan <shuah@...nel.org>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Jose Abreu <joabreu@...opsys.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, bpf@...r.kernel.org,
        xdp-hints@...-project.net,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org,
        linux-kselftest@...r.kernel.org
Subject: Re: [PATCH bpf-next v2 2/3] net: stmmac: Add txtime support to XDP ZC



On 12/1/23 07:24, Song Yoong Siang wrote:
> This patch enables txtime support to XDP zero copy via XDP Tx
> metadata framework.
> 
> Signed-off-by: Song Yoong Siang<yoong.siang.song@...el.com>
> ---
>   drivers/net/ethernet/stmicro/stmmac/stmmac.h      |  2 ++
>   drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 13 +++++++++++++
>   2 files changed, 15 insertions(+)

I think we need to see other drivers using this new feature to evaluate
if API is sane.

I suggest implementing this for igc driver (chip i225) and also for igb
(i210 chip) that both support this kind of LaunchTime feature in HW.

The API and stmmac driver takes a u64 as time.
I'm wondering how this applies to i210 that[1] have 25-bit for
LaunchTime (with 32 nanosec granularity) limiting LaunchTime max 0.5
second into the future.
And i225 that [1] have 30-bit max 1 second into the future.


[1] 
https://github.com/xdp-project/xdp-project/blob/master/areas/tsn/code01_follow_qdisc_TSN_offload.org