netdev - Re: [net-next 03/15] net/mlx5: Add adjphase function to support hardware-only offset control

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Message-ID: <20230119194631.1b9fef95@kernel.org>
Date:   Thu, 19 Jan 2023 19:46:31 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Jacob Keller <jacob.e.keller@...el.com>
Cc:     Saeed Mahameed <saeed@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Paolo Abeni <pabeni@...hat.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Saeed Mahameed <saeedm@...dia.com>, <netdev@...r.kernel.org>,
        Tariq Toukan <tariqt@...dia.com>,
        Rahul Rameshbabu <rrameshbabu@...dia.com>,
        Gal Pressman <gal@...dia.com>,
        Richard Cochran <richardcochran@...il.com>
Subject: Re: [net-next 03/15] net/mlx5: Add adjphase function to support
 hardware-only offset control

On Wed, 18 Jan 2023 13:33:56 -0800 Jacob Keller wrote:
> > The adjtime function supports using hardware to set the clock offset when
> > the delta was supported by the hardware. When the delta is not supported by
> > the hardware, the driver handles adjusting the clock. The newly-introduced
> > adjphase function is similar to the adjtime function, except it guarantees
> > that a provided clock offset will be used directly by the hardware to
> > adjust the PTP clock. When the range is not acceptable by the hardware, an
> > error is returned.
> 
> Makes sense. Once you've verified that the delta is within the accepted
> range you can just re-use the existing adjtime function.

Seems like we should add a "max_time_adj" to struct ptp_clock_info
and let the core call adjphase if the offset is small enough to fit.
Instead of having all drivers redirect the calls internally.