Voltage levels at different frequencies

Robotics & Edge Computing Jetson & Embedded Systems Jetson TK1
1

Hi.

Is there any information on what voltage the GPU is running on for different frequencies?

When you type
cat /sys/kernel/debug/clock/gbus/possible_rates

It shows that the GPU clock can have a number of different values.
72000 108000 180000 252000 324000 396000 468000 540000 612000 648000 684000 708000 756000 804000 852000 (kHz)

I assume that at lower frequencies, the voltage levels go down (DVFS).
Are there any tools or commands or files you can check to see the current voltage level?

Thank you.

2

I think this is the right way to do it:

Dump current DVFS-controlled voltages and frequencies:

sudo cat /sys/kernel/debug/clock/dvfs

Inspect static DVFS table:

sudo cat /sys/kernel/debug/clock/dvfs_table
3

Thank you so much!

4

I’m reviving quite an old thread here so don’t flame at me.

Is there a way to change the voltages within the DVFS table? I’ve used the:

VDD_GPU_offs

or

VDD_CORE_offs
VDD_CPU_offs

and it appears there’s not really a change in voltage scaling. If I set the CORE_Offs to something under -90 it’ll reboot the system. My understand was that the offs was an offset voltage that you could use to alter the vdd voltage…apparently not based on my power draws and temperatures… Any help would be great!

5

Furthermore:
In the DVFS table I get the following:
Located:

sys/kernel/debug/clock/cat dvfs

vdd_cpu 1100mV dfll Mode:
nominal     1260 mV
offset      0    mV
thermal     820  mV
cpu_G       249900000000 1100 mV
vdd_core 950 mV
nominal 1150 mV
offset -60 mV
override 0 mV [1100...1150]

I’m maybe thinking the override function will work?

6

There is no CPU voltage scaling method and user should not modify the DVFS table as it’s generated by memory characterization tool.

You could refer to Jetson/Performance - eLinux.org to maximize or minimize CPU & GPU clocks for different performance & power draw on your test.

Cheers