argen96

Hi @jock & @hexdump Thanks for the reply, very interesting. The way I came to the fixed voltage conclusion was by looking at the reference design of the buck regulator IC on the board. There are 3 SOT-23 ICs marked "AS20B5". Here is what I found online: https://uccpd.com/article/97.mhtml Then I probed on the inductor with a DMM to measure the output voltage. In the reference design, the regulator output voltage is set by a voltage divider relation between R1 and R2. However, you may be right, if the circuit on the board feeds the output of RK3318 PWM into that resistor network, then I guess the SOC could in effect modify the output voltage by using its PWM controllers. Chinese designers come up with some clever cost cutting ideas, would be great. I don't have schematics, actually could not even find the datasheet for RK3318, I assume it is an RK3328 with 100Mbps ethernet which is the only difference I found. If you have a dts/dtb file for current kernels on similar boards I would love to give it a try. Thanks, Jose

I reply myself , for the record in case someone has the same board / issue. My PCB has a black solder mask and is marked in silkscreen as "RK3318_V1.2" . Upon inspecting the PCB I see that it does not have a proper power management IC. Instead it has 3 discrete switching regulators which output 3.3V, 1.18v and 1.15v respectively. These regulators have a fixed output voltage set by resistors so the 'dynamic' voltage frequency scaling through 'operating-points' is out of question. However throttling the CPU frequencies may be possible if not pushed beyond the limit set by the supply voltage. I will keep researching if anyone can point me towards some relevant info I would appreciate it.

Hello everyone, I have an rk3318 h96 max , 2gb, 16gb configuration. I've followed installation but couldn't get frequency scaling working. (/sys/devices/system/cpu/cpu0/cpufreq/ is empty) I am wondering if anyone can confirm that it works with the latest images. If it does work maybe there is something wrong with my dtb file. Thank you! Regards, Jose