RE: [PATCH] net: lan743x_ptp: convert to ktime_get_clocktai_ts64

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Question: this is the only ptp driver that sets the hardware
time to the current system time in TAI. Why does it do that?

This is done when the driver starts up after reset. Otherwise the
clock is off

by 48 years.

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It seemed to me that the system time was the most appropriate
clock to

sync to.

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If my reasoning is incorrect, please enlighten me.

I've never worked with PTP, but my understanding from looking at the
other drivers is that the time normally gets set either from another
host through the PTP protocol, or using clock_settime() from user
space with the current time.

Those methods will still work. But if it's not set by those methods, I
thought the clock should at least be set once on driver startup to align with

the system clock.

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After that, other methods are free to reset it again.

(adding Richard Cochran to Cc for more insight here)

I would argue that it's more important that the driver behaves like all other
PTP implementations. If we want the behavior to be that the initial PTP time
is set to the ktime_get_clocktai_ts64() value, then this should be done by the
PTP core rather than the device driver. If there is a good reason that the
other drivers don't do it like this, then I would assume the same reason
applies to lan743x.

Sounds reasonable to me. I will yield to Richard's insight.
But it would be nice if requirements like these were documented.