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

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Message-ID: <4ba02d13a8c14045b0df7deaee188f82@amazon.com>
Date: Tue, 5 Nov 2024 16:52:11 +0000
From: "Arinzon, David" <darinzon@...zon.com>
To: Gal Pressman <gal@...dia.com>, Jakub Kicinski <kuba@...nel.org>
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>, "Rahul
 Rameshbabu" <rrameshbabu@...dia.com>
Subject: RE: [PATCH v3 net-next 3/3] net: ena: Add PHC documentation

> >>> +=================
> >> ======================================================
> >>> +**phc_cnt**         Number of successful retrieved timestamps (below
> >> expire timeout).
> >>> +**phc_exp**         Number of expired retrieved timestamps (above
> >> expire timeout).
> >>> +**phc_skp**         Number of skipped get time attempts (during block
> >> period).
> >>> +**phc_err**         Number of failed get time attempts (entering into
> block
> >> state).
> >>> +=================
> >> ======================================================
> >>
> >> I seem to recall we had an unpleasant conversation about using
> >> standard stats recently. Please tell me where you looked to check if
> >> Linux has standard stats for packet timestamping. We need to add the
> right info there.
> >> --
> >> pw-bot: cr
> >
> > Hi Jakub,
> >
> > 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.
> > We reviewed similar drivers that support HW timestamping via
> > `gettime64` and `gettimex64` APIs, and we couldn't identify any that
> capture or report statistics related to reading a HW timestamp.
> > Let us know if further details would be helpful.
> 
> David, did you consider Rahul's recent timestamping stats API?
> 0e9c127729be ("ethtool: add interface to read Tx hardware timestamping
> statistics")

Hi Gal,

We've looked into the `get_ts_stats` ethtool hook, and it refers to TX HW packet timestamping
and not HW timestamp which is retrieved through `gettime64` and `gettimex64`.