linux-kernel - Re: [PATCH net-next v3] net: micrel: Change to receive timestamp in the frame for lan8841

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Message-ID: <ZJMASvms7nLY8HKz@hoboy.vegasvil.org>
Date:   Wed, 21 Jun 2023 06:51:06 -0700
From:   Richard Cochran <richardcochran@...il.com>
To:     Horatiu Vultur <horatiu.vultur@...rochip.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        andrew@...n.ch, hkallweit1@...il.com, linux@...linux.org.uk,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com
Subject: Re: [PATCH net-next v3] net: micrel: Change to receive timestamp in
 the frame for lan8841

On Thu, Jun 15, 2023 at 11:47:40AM +0200, Horatiu Vultur wrote:
> Currently for each timestamp frame, the SW needs to go and read the
> received timestamp over the MDIO bus. But the HW has the capability
> to store the received nanoseconds part and the least significant two
> bits of the seconds in the reserved field of the PTP header. In this
> way we could save few MDIO transactions (actually a little more
> transactions because the access to the PTP registers are indirect)
> for each received frame.
> 
> Instead of reading the rest of seconds part of the timestamp of the
> frame using MDIO transactions schedule PTP worker thread to read the
> seconds part every 500ms and then for each of the received frames use
> this information. Because if for example running with 512 frames per
> second, there is no point to read 512 times the second part.
> 
> Doing all these changes will give a great CPU usage performance.
> Running ptp4l with logSyncInterval of -9 will give a ~60% CPU
> improvement.
> 
> Signed-off-by: Horatiu Vultur <horatiu.vultur@...rochip.com>

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