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Message-ID: <7733369a-c3a6-89d4-fb32-ab2bcdc1def0@linux.intel.com>
Date:   Sun, 30 Apr 2023 08:03:06 +0300
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Subject: Re: [Intel-wired-lan] [PATCH net 1/1] igc: read before write to
 SRRCTL register
Content-Language: en-US
To:     Song Yoong Siang <yoong.siang.song@intel.com>,
        Jesse Brandeburg <jesse.brandeburg@intel.com>,
        Tony Nguyen <anthony.l.nguyen@intel.com>,
        "David S . Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Jesper Dangaard Brouer <hawk@kernel.org>,
        John Fastabend <john.fastabend@gmail.com>,
        Maciej Fijalkowski <maciej.fijalkowski@intel.com>,
        Vedang Patel <vedang.patel@intel.com>,
        Jithu Joseph <jithu.joseph@intel.com>,
        Andre Guedes <andre.guedes@intel.com>,
        Jesper Dangaard Brouer <brouer@redhat.com>,
        Stanislav Fomichev <sdf@google.com>
Cc:     xdp-hints@xdp-project.net, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, stable@vger.kernel.org,
        intel-wired-lan@lists.osuosl.org, bpf@vger.kernel.org
References: <20230413151222.1864307-1-yoong.siang.song@intel.com>
From:   "naamax.meir" <naamax.meir@linux.intel.com>
In-Reply-To: <20230413151222.1864307-1-yoong.siang.song@intel.com>
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On 4/13/2023 18:12, 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.
> 
> Thus, this commit read the register value before write to SRRCTL
> register. This commit is tested by using xdp_hw_metadata bpf selftest
> tool. The tool enables Rx hardware timestamp and then attach XDP program
> to igc driver. It will display hardware timestamp of UDP packet with
> port number 9092. Below are detail of test steps and results.
> 
> Command on DUT:
>    sudo ./xdp_hw_metadata <interface name>
> 
> Command on Link Partner:
>    echo -n skb | nc -u -q1 <destination IPv4 addr> 9092
> 
> Result before this patch:
>    skb hwtstamp is not found!
> 
> Result after this patch:
>    found skb hwtstamp = 1677762212.590696226
> 
> Fixes: fc9df2a0b520 ("igc: Enable RX via AF_XDP zero-copy")
> Cc: <stable@vger.kernel.org> # 5.14+
> Signed-off-by: Song Yoong Siang <yoong.siang.song@intel.com>
> ---
>   drivers/net/ethernet/intel/igc/igc_base.h | 7 +++++--
>   drivers/net/ethernet/intel/igc/igc_main.c | 5 ++++-
>   2 files changed, 9 insertions(+), 3 deletions(-)

Tested-by: Naama Meir <naamax.meir@linux.intel.com>