Disable 4 main cores and run on 5th low power core

[Jimmy_Pettersson]

Hi,

I’ve been trying to turn off all the main cores and only try working on the 5th low power core.

I followed the short description here:
http://elinux.org/Jetson/Performance

Restricting to low-power core only
Restricting the CPU to the low-power companion core can significantly reduce peak power (if running on a power-limited battery pack, for example). The 5th companion core in Tegra K1 is still a Cortex-A15 core with NEON and 32KB L1 cache and 512KB L2 private cache, but obviously at lower performance than the 4 main cores. To use just the low-power core, run this as root:

echo 0 > /sys/devices/system/cpu/cpuquiet/tegra_cpuquiet/enable
echo LP > /sys/kernel/cluster/active

But I get:

write error: Dervice or resource busy

What am I doing wrong here? What’s the work around?

EDIT: Perhaps the commands need to be added to some startup script?

[kulve]

Which one of the echo commands gives you the device busy error?

[Jimmy_Pettersson]

Last one:

echo LP > /sys/kernel/cluster/active

[Jimmy_Pettersson]

shameless bump ;-)

[ShervinE]

It turns out that the Wiki was missing some info. So I’ve updated the Wiki to show how to check which cluster & cores & frequencies you are currently running at, and how to switch purely to the 5th shadow core:

• http://elinux.org/Jetson/Performance#Viewing_the_current_CPU_status
• http://elinux.org/Jetson/Performance#Restricting_to_low-power_core_only

[Jimmy_Pettersson]

Thanks Shervin, will give it another go in little while and update you on the results.