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Date:   Fri, 1 Dec 2023 16:02:22 +0100
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Subject: Re: [PATCH bpf-next v2 2/3] net: stmmac: Add txtime support to XDP ZC
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To:     Song Yoong Siang <yoong.siang.song@intel.com>,
        "David S . Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Bjorn Topel <bjorn@kernel.org>,
        Magnus Karlsson <magnus.karlsson@intel.com>,
        Maciej Fijalkowski <maciej.fijalkowski@intel.com>,
        Jonathan Lemon <jonathan.lemon@gmail.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        John Fastabend <john.fastabend@gmail.com>,
        Stanislav Fomichev <sdf@google.com>,
        Lorenzo Bianconi <lorenzo@kernel.org>,
        Tariq Toukan <tariqt@nvidia.com>,
        Willem de Bruijn <willemb@google.com>,
        Maxime Coquelin <mcoquelin.stm32@gmail.com>,
        Andrii Nakryiko <andrii@kernel.org>,
        Mykola Lysenko <mykolal@fb.com>,
        Martin KaFai Lau <martin.lau@linux.dev>,
        Song Liu <song@kernel.org>,
        Yonghong Song <yonghong.song@linux.dev>,
        KP Singh <kpsingh@kernel.org>, Hao Luo <haoluo@google.com>,
        Jiri Olsa <jolsa@kernel.org>, Shuah Khan <shuah@kernel.org>,
        Alexandre Torgue <alexandre.torgue@foss.st.com>,
        Jose Abreu <joabreu@synopsys.com>
Cc:     netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-doc@vger.kernel.org, bpf@vger.kernel.org,
        xdp-hints@xdp-project.net,
        linux-stm32@st-md-mailman.stormreply.com,
        linux-arm-kernel@lists.infradead.org,
        linux-kselftest@vger.kernel.org
References: <20231201062421.1074768-1-yoong.siang.song@intel.com>
 <20231201062421.1074768-3-yoong.siang.song@intel.com>
From:   Jesper Dangaard Brouer <hawk@kernel.org>
In-Reply-To: <20231201062421.1074768-3-yoong.siang.song@intel.com>
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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@intel.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