netdev - Re: [PATCH v2] ptp_qoriq: fix latency in ptp_qoriq

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Message-ID: <20230119225301.tjf5cxaigokho4nf@skbuf>
Date:   Fri, 20 Jan 2023 00:53:01 +0200
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     nikhil.gupta@....com
Cc:     linux-arm-kernel@...ts.infradead.org,
        Yangbo Lu <yangbo.lu@....com>, richardcochran@...il.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        vakul.garg@....com, rajan.gupta@....com
Subject: Re: [PATCH v2] ptp_qoriq: fix latency in ptp_qoriq_adjtime()
 operation

On Fri, Jan 20, 2023 at 02:10:34AM +0530, nikhil.gupta@....com wrote:
> From: Nikhil Gupta <nikhil.gupta@....com>
> 
> 1588 driver loses about 1us in adjtime operation at PTP slave
> This is because adjtime operation uses a slow non-atomic tmr_cnt_read()
> followed by tmr_cnt_write() operation.
> 
> In the above sequence, since the timer counter operation keeps
> incrementing, it leads to latency. The tmr_offset register
> (which is added to TMR_CNT_H/L register giving the current time)
> must be programmed with the delta nanoseconds.
> 
> Signed-off-by: Nikhil Gupta <nikhil.gupta@....com>
> ---

Reviewed-by: Vladimir Oltean <vladimir.oltean@....com>
Tested-by: Vladimir Oltean <vladimir.oltean@....com>

One detail regarding the process: you should have clarified your
expectations, i.e. the patch should have explicitly been generated with
git send-email --subject-prefix='PATCH v2 net-next' since it is not
targeting the 'net.git' tree for bug fixes on the master branch (which
are also backported to stable trees), but rather will be included in the
pull request for the upcoming 6.3 kernel.