netdev - RE: [PATCH net v3 1/1] igc: read before write to SRRCTL register

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Date:   Sun, 16 Apr 2023 02:19:26 +0000
From:   "Song, Yoong Siang" <yoong.siang.song@...el.com>
To:     "Bezdeka, Florian" <florian.bezdeka@...mens.com>,
        "Brandeburg, Jesse" <jesse.brandeburg@...el.com>,
        "Nguyen, Anthony L" <anthony.l.nguyen@...el.com>,
        "David S . Miller" <davem@...emloft.net>,
        "Eric Dumazet" <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        "John Fastabend" <john.fastabend@...il.com>,
        "Fijalkowski, Maciej" <maciej.fijalkowski@...el.com>,
        Vedang Patel <vedang.patel@...el.com>,
        "Joseph, Jithu" <jithu.joseph@...el.com>,
        Andre Guedes <andre.guedes@...el.com>,
        "Brouer, Jesper" <brouer@...hat.com>,
        "Stanislav Fomichev" <sdf@...gle.com>,
        "Keller, Jacob E" <jacob.e.keller@...el.com>,
        David Laight <David.Laight@...LAB.COM>
CC:     "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "xdp-hints@...-project.net" <xdp-hints@...-project.net>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: RE: [PATCH net v3 1/1] igc: read before write to SRRCTL register

On Saturday, April 15, 2023 5:20 PM, Florian Bezdeka <florian.bezdeka@...mens.com> wrote:
>On 14.04.23 17:49, Song Yoong Siang wrote:
>> igc_configure_rx_ring() function will be called as part of XDP program
>> setup. If Rx hardware timestamp is enabled prio to XDP program setup,
>> this timestamp enablement will be overwritten when buffer size is
>> written into SRRCTL register.
>>
>
>Hi all,
>
>I'm actually searching for the root cause of a similar problem (RX timestamp lost)
>that I can reproduce here, but the setup is slightly different. The setup:
>
>- igc driver
>- i225/226 network card
>- When starting to transmit frames using XDP with zero copy enabled
>  another application (ptp4l) complains about missing RX timestamps
>- Loading the XDP program has already been removed (not needed for
>  TX only)
>- ptp4l is using the traditional socket API
>- The RX timestamps seem to come back once we stop sending frames
>  using XDP
>
>The "zero copy support" enabled part is important. If ZC support is not requested
>everything works fine.
>
>Any ideas?
>
>Best regards,
>Florian
>

Hi Florian,

You means this patch does not help on your issue?
Need to understand more on the setup and behavior to tell.
Are ptp4l and XDP ZC Tx apps running on same queue or separate queue?
I suggest you to run " sudo hwstamp_ctl -i eth0 -r 1 " multiple times in the middle
to check the behavior.

Thanks & Regards
Siang