On Tue, Feb 13, 2018 at 07:01:22PM +0100, Oliver Westermann wrote:
> The issue is that the PHY only has two slots for timestamps, one for
> outgoing packages and one for incoming packages. If the device in question
> is a ptp master and has multiple slave, it sometimes happen that both
> DELAY_REQ packages come in short succession, which results in the PHY
> driver/interrupt handler being to slow to get all timestamps.

This is actually a bug in your driver.  If an incoming delay request
misses a time stamp, no fault is generated.  The *transmit* time stamp
is still available, but your driver fails to fetch it.

> From a PTP perspective this is not a big issue: A single missing delay
> measurement doesn't break a clock.


> But PTP4L threats this as a critical error, printing
> "timed out while polling for tx timestamp",

This should not happen.  You should fix your driver so that it always
fetches the Tx time stamp after sending a marked packet.  No interrupt
is necessary.


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