netdev - Re: [PATCH v3 net-next 3/3] net: ena: Add PHC documentation

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Message-ID: <20241105172858.273df3fd@kernel.org>
Date: Tue, 5 Nov 2024 17:28:58 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: "Arinzon, David" <darinzon@...zon.com>
Cc: David Miller <davem@...emloft.net>, "netdev@...r.kernel.org"
 <netdev@...r.kernel.org>, Eric Dumazet <edumazet@...gle.com>, Paolo Abeni
 <pabeni@...hat.com>, Richard Cochran <richardcochran@...il.com>,
 "Woodhouse, David" <dwmw@...zon.co.uk>, "Machulsky, Zorik"
 <zorik@...zon.com>, "Matushevsky, Alexander" <matua@...zon.com>, "Bshara,
 Saeed" <saeedb@...zon.com>, "Wilson, Matt" <msw@...zon.com>, "Liguori,
 Anthony" <aliguori@...zon.com>, "Bshara, Nafea" <nafea@...zon.com>,
 "Schmeilin, Evgeny" <evgenys@...zon.com>, "Belgazal, Netanel"
 <netanel@...zon.com>, "Saidi, Ali" <alisaidi@...zon.com>, "Herrenschmidt,
 Benjamin" <benh@...zon.com>, "Kiyanovski, Arthur" <akiyano@...zon.com>,
 "Dagan, Noam" <ndagan@...zon.com>, "Bernstein, Amit" <amitbern@...zon.com>,
 "Agroskin, Shay" <shayagr@...zon.com>, "Abboud, Osama"
 <osamaabb@...zon.com>, "Ostrovsky, Evgeny" <evostrov@...zon.com>,
 "Tabachnik, Ofir" <ofirt@...zon.com>, "Machnikowski, Maciek"
 <maciek@...hnikowski.net>
Subject: Re: [PATCH v3 net-next 3/3] net: ena: Add PHC documentation

On Tue, 5 Nov 2024 10:52:12 +0000 Arinzon, David wrote:
> Just wanted to clarify that this feature and the associated
> documentation are specifically intended for reading a HW timestamp,
> not for TX/RX packet timestamping.

Oh, so you're saying you can only read the clock from the device?
The word timestamp means time associated with an event.

In the doc you talk about:

> +PHC support and capabilities can be verified using ethtool:
> +
> +.. code-block:: shell
> +
> +  ethtool -T <interface>

which is for packet timestamping

also:

> ENA Linux driver supports PTP hardware clock providing timestamp
> reference to achieve nanosecond accuracy.

You probably want to double check the definitions of accuracy and
resolution.

We recently merged an Amazon PTP clock driver from David Woodhouse, 
see commit 20503272422693. If you're not timestamping packets why
not use that driver?