https://github.com/torvalds/linux
Revision 0ba83aa037da456bb73868e5cc20558c5a644414 authored by Vladimir Oltean on 06 May 2020, 17:48:13 UTC, committed by David S. Miller on 06 May 2020, 22:03:14 UTC
It looks like the sja1105 external timestamping input is not as generic as we thought. When fed a signal with 50% duty cycle, it will timestamp both the rising and the falling edge. When fed a short pulse signal, only the timestamp of the falling edge will be seen in the PTPSYNCTS register, because that of the rising edge had been overwritten. So the moral is: don't feed it short pulse inputs. Luckily this is not a complete deal breaker, as we can still work with 1 Hz square waves. But the problem is that the extts polling period was not dimensioned enough for this input signal. If we leave the period at half a second, we risk losing timestamps due to jitter in the measuring process. So we need to increase it to 4 times per second. Also, the very least we can do to inform the user is to deny any other flags combination than with PTP_RISING_EDGE and PTP_FALLING_EDGE both set. Fixes: 747e5eb31d59 ("net: dsa: sja1105: configure the PTP_CLK pin as EXT_TS or PER_OUT") Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com> Acked-by: Richard Cochran <richardcochran@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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Tip revision: 0ba83aa037da456bb73868e5cc20558c5a644414 authored by Vladimir Oltean on 06 May 2020, 17:48:13 UTC
net: dsa: sja1105: the PTP_CLK extts input reacts on both edges
net: dsa: sja1105: the PTP_CLK extts input reacts on both edges
Tip revision: 0ba83aa
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