Which clock is used in GTE timestamps?

Robotics & Edge Computing Jetson & Embedded Systems Jetson Xavier NX
1

In Welcome — Jetson Linux<br/>Developer Guide 34.1 documentation

gte_mon prints “HW timestamp GPIO EVENT xxxx.”

What is the clock of this timestamp? How can I read this clock used by GPIO timestamps so that I can correlate the GPIO timestamps to system time? The clock was not the same with CLOCK_MONOTONIC in my tests.

3

hello xlz,

it’s TSC for hardware timestamp.
you may also refer to forum discussion thread, Topic 78821 for the details of timestamps.
thanks

4

Ah yes, thanks.

This is documented by the NVIDIA Xavier Series System-on-ChipTechnical Reference Manual, section 8.1.2.21.8 Timestamping (GTE): The AON cluster implements a timestamp module (GTE) for logging the current TSC value when interrupts or GPIO events occur.

The TSC can be read with

int64_t tsc;
asm volatile("mrs %0, cntvct_el0" : "=r"(tsc));
int64_t freq;
asm volatile("mrs %0, cntfrq_el0" : "=r"(freq));

freq should be 31.25M.