I found only this command:
It work at kernel 4.9 and would be also work at kernel 5.15 (but not in this time not in coreelec 22NO):
cat /sys/class/mpgpu/cur_freq
In ondemand and performance modeis freq at value: only 800 as default (boost) without change up or down at my device Ugoos am6plus with s922xj at CE21NG. In CE22NO is not working - can not open due to no exist file or directory.