Free-running System Timer Equivalent

Hi there! I’m working on porting a user-space Linux service that currently runs on the Raspberry Pi family. This app makes heavy use of the free-running, 64-bit system timer counter in the BCM family of CPUs (Page 172 of https://datasheets.raspberrypi.com/bcm2835/bcm2835-peripherals.pdf). I’ve been trying to find an equivalent to this in the Allwinner series of processors.

One option that I’ve been exploring is to use the high speed timer function. However, I haven’t had any success using these registers from user space. I’m using mmap to access the registers directly. When I read the data it always seems to be zero.

Are there any good examples out there of using the high speed timer function from user space? (I found an example kernel driver) Or, does anyone have any suggestions on how I could access a 64-bit free running counter from user space?

Thanks in advance!