netdev - Re: [PATCH net-next 1/9] ptp: Clarify ptp_clock_info .adjphase expects an internal servo to be used

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Message-ID: <ZGvLm0Cxh+skT6zB@hoboy.vegasvil.org>
Date: Mon, 22 May 2023 13:07:55 -0700
From: Richard Cochran <richardcochran@...il.com>
To: Rahul Rameshbabu <rrameshbabu@...dia.com>
Cc: netdev@...r.kernel.org, Saeed Mahameed <saeed@...nel.org>,
	Gal Pressman <gal@...dia.com>, Tariq Toukan <tariqt@...dia.com>,
	"David S. Miller" <davem@...emloft.net>,
	Jakub Kicinski <kuba@...nel.org>,
	Jacob Keller <jacob.e.keller@...el.com>
Subject: Re: [PATCH net-next 1/9] ptp: Clarify ptp_clock_info .adjphase
 expects an internal servo to be used

On Mon, May 22, 2023 at 10:03:23AM -0700, Rahul Rameshbabu wrote:

> This point makes sense to me. However, I have a concern about the case
> where the linuxptp servo has not had a chance to make a single frequency
> adjustment (0 ppb) and .adjphase/LOCKED_STABLE state is initially
> called/reached. After converging, the frequency will be close to the
> remote time's server's frequency, but that frequency will likely not be
> 0 ppb. If .adjfine had been called previously, the difference between
> the remote time server's frequency and the cached frequency in the ptp
> stack would likely be significantly closer. That said, do you think it
> makes sense to have some kind of API that gives information about the
> in-HW controller such as the frequency offset it operated? Or maybe in
> general an API in the future for introspecting the state of this in-HW
> servo?

The whole point of hardware vendors doing this is to hide their
implementation from prying eyes.  So they are not going to provide
introspection at all.

Thanks,
Richard