netdev - Re: [PATCH net-next] net: ethernet: ti: am65-cpts: adjust estf following ptp changes

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Date:   Tue, 21 Mar 2023 21:19:39 -0700
From:   Richard Cochran <richardcochran@...il.com>
To:     Siddharth Vadapalli <s-vadapalli@...com>
Cc:     davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, rogerq@...nel.org, jacob.e.keller@...el.com,
        leon@...nel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        srk@...com
Subject: Re: [PATCH net-next] net: ethernet: ti: am65-cpts: adjust estf
 following ptp changes

On Tue, Mar 21, 2023 at 11:56:00AM +0530, Siddharth Vadapalli wrote:
> From: Grygorii Strashko <grygorii.strashko@...com>
> 
> When the CPTS clock is synced/adjusted by running linuxptp (ptp4l/phc2sys),
> it will cause the TSN EST schedule to drift away over time. This is because
> the schedule is driven by the EstF periodic counter whose pulse length is
> defined in ref_clk cycles and it does not automatically sync to CPTS clock.
>    _______
>  _|
>   ^
>   expected cycle start time boundary
>    _______________
>  _|_|___|_|
>   ^
>   EstF drifted away -> direction
> 
> To fix it, the same PPM adjustment has to be applied to EstF as done to the
> PHC CPTS clock, in order to correct the TSN EST cycle length and keep them
> in sync.
> 
> Drifted cycle:
> AM65_CPTS_EVT: 7 e1:01770001 e2:000000ff t:1635968230373377017
> AM65_CPTS_EVT: 7 e1:01770001 e2:000000ff t:1635968230373877017
> AM65_CPTS_EVT: 7 e1:01770001 e2:000000ff t:1635968230374377017
> AM65_CPTS_EVT: 7 e1:01770001 e2:000000ff t:1635968230374877017
> AM65_CPTS_EVT: 7 e1:01770001 e2:000000ff t:1635968230375377017
> AM65_CPTS_EVT: 7 e1:01770001 e2:000000ff t:1635968230375877023
> AM65_CPTS_EVT: 7 e1:01770001 e2:000000ff t:1635968230376377018
> AM65_CPTS_EVT: 7 e1:01770001 e2:000000ff t:1635968230376877018
> AM65_CPTS_EVT: 7 e1:01770001 e2:000000ff t:1635968230377377018
> 
> Stable cycle:
> AM65_CPTS_EVT: 7 e1:01770001 e2:000000ff t:1635966863193375473
> AM65_CPTS_EVT: 7 e1:01770001 e2:000000ff t:1635966863193875473
> AM65_CPTS_EVT: 7 e1:01770001 e2:000000ff t:1635966863194375473
> AM65_CPTS_EVT: 7 e1:01770001 e2:000000ff t:1635966863194875473
> AM65_CPTS_EVT: 7 e1:01770001 e2:000000ff t:1635966863195375473
> AM65_CPTS_EVT: 7 e1:01770001 e2:000000ff t:1635966863195875473
> AM65_CPTS_EVT: 7 e1:01770001 e2:000000ff t:1635966863196375473
> 
> Signed-off-by: Grygorii Strashko <grygorii.strashko@...com>
> Signed-off-by: Siddharth Vadapalli <s-vadapalli@...com>

Acked-by: Richard Cochran <richardcochran@...il.com>