On Wed, Apr 12, 2017 at 02:30:51PM +0000, Ian Thompson wrote:
> If I do "adjtimex -p", I get a raw time e.g. 1492005529.681665099.
I assume that is some wrapper program around the adjtimex system call?
> This is system time, but is it TAI, Unix time or UTC?
The system call...
ADJTIMEX(2) Linux Programmer's Manual ADJTIMEX(2)
NAME
adjtimex - tune kernel clock
SYNOPSIS
#define _BSD_SOURCE /* See feature_test_macros(7) */
#include <sys/timex.h>
int adjtimex(struct timex *buf);
... returns UTC.
> I was assuming it was seconds from 00:00:00 UTC without leap seconds.
UTC always includes leap seconds by definition.
> We are trying to timestamp some data collection with GPS time.
> The stmicro MAC has an auxiliary register that can be updated with the clock
> registers on an external event.
> We clock that event at 4kHz and use the values in the auxiliary registers to
> form the timestamp, which is a single 64bit value in uSeconds.
> This value always seems to be 37 seconds off, even if I "correct"
> stmmac_hwtstamp_ioctl to not use UTC.
>
> Is there something wrong with my thinking?
I am not sure. Do you read /dev/ptpX to get those time stamps?
What does 'testptp -c' say about your device?
Thanks,
Richard
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