netdev - Re: [PATCH iwl-net 1/3] ice: remove ptp

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Date: Sat, 4 Nov 2023 11:23:41 -0400
From: Simon Horman <horms@...nel.org>
To: Jacob Keller <jacob.e.keller@...el.com>
Cc: Anthony Nguyen <anthony.l.nguyen@...el.com>,
	Intel Wired LAN <intel-wired-lan@...ts.osuosl.org>,
	netdev@...r.kernel.org,
	Jesse Brandeburg <jesse.brandeburg@...el.com>
Subject: Re: [PATCH iwl-net 1/3] ice: remove ptp_tx ring parameter flag

On Fri, Nov 03, 2023 at 04:46:56PM -0700, Jacob Keller wrote:
> Before performing a Tx timestamp in ice_stamp(), the driver checks a ptp_tx
> ring variable to see if timestamping is enabled on that ring. This value is
> set for all rings whenever userspace configures Tx timestamping.
> 
> Ostensibly this was done to avoid wasting cycles checking other fields when
> timestamping has not been enabled. However, for Tx timestamps we already
> get an individual per-SKB flag indicating whether userspace wants to
> request a timestamp on that packet. We do not gain much by also having
> a separate flag to check for whether timestamping was enabled.
> 
> In fact, the driver currently fails to restore the field after a PF reset.
> Because of this, if a PF reset occurs, timestamps will be disabled.
> 
> Since this flag doesn't add value in the hotpath, remove it and always
> provide a timestamp if the SKB flag has been set.
> 
> A following change will fix the reset path to properly restore user
> timestamping configuration completely.
> 
> This went unnoticed for some time because one of the most common
> applications using Tx timestamps, ptp4l, will reconfigure the socket as
> part of its fault recovery logic.
> 
> Fixes: ea9b847cda64 ("ice: enable transmit timestamps for E810 devices")
> Signed-off-by: Jacob Keller <jacob.e.keller@...el.com>
> Reviewed-by: Jesse Brandeburg <jesse.brandeburg@...el.com>

Reviewed-by: Simon Horman <horms@...nel.org>