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

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Message-ID: <20230503080753.GE525452@unreal>
Date: Wed, 3 May 2023 11:07:53 +0300
From: Leon Romanovsky <leon@...nel.org>
To: Tony Nguyen <anthony.l.nguyen@...el.com>
Cc: davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com,
	edumazet@...gle.com, netdev@...r.kernel.org,
	Song Yoong Siang <yoong.siang.song@...el.com>,
	sasha.neftin@...el.com, maciej.fijalkowski@...el.com,
	magnus.karlsson@...el.com, ast@...nel.org, daniel@...earbox.net,
	hawk@...nel.org, john.fastabend@...il.com, bpf@...r.kernel.org,
	stable@...r.kernel.org, Jacob Keller <jacob.e.keller@...el.com>,
	Jesper Dangaard Brouer <brouer@...hat.com>,
	Naama Meir <naamax.meir@...ux.intel.com>
Subject: Re: [PATCH net 1/1] igc: read before write to SRRCTL register

On Tue, May 02, 2023 at 08:48:06AM -0700, Tony Nguyen wrote:
> From: Song Yoong Siang <yoong.siang.song@...el.com>
> 
> 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 = 1677800973.642836757
> 
> Optionally, read PHC to confirm the values obtained are almost the same:
> Command:
>   sudo ./testptp -d /dev/ptp0 -g
> Result:
>   clock time: 1677800973.913598978 or Fri Mar  3 07:49:33 2023
> 
> Fixes: fc9df2a0b520 ("igc: Enable RX via AF_XDP zero-copy")
> Cc: <stable@...r.kernel.org> # 5.14+
> Signed-off-by: Song Yoong Siang <yoong.siang.song@...el.com>
> Reviewed-by: Jacob Keller <jacob.e.keller@...el.com>
> Reviewed-by: Jesper Dangaard Brouer <brouer@...hat.com>
> Tested-by: Jesper Dangaard Brouer <brouer@...hat.com>
> Tested-by: Naama Meir <naamax.meir@...ux.intel.com>
> Signed-off-by: Tony Nguyen <anthony.l.nguyen@...el.com>
> ---
>  drivers/net/ethernet/intel/igc/igc_base.h | 11 ++++++++---
>  drivers/net/ethernet/intel/igc/igc_main.c |  7 +++++--
>  2 files changed, 13 insertions(+), 5 deletions(-)
> 

Thanks,
Reviewed-by: Leon Romanovsky <leonro@...dia.com>