[DEV][KERNEL] Tegra3 power management notes and tricks
This thread contains findings on how to view and set kernel parameters related to power management. Although there is no kernel source for One X, some information can be obtained from Transformer Prime kernel sources (also a Tegra 3 device), and from the device itself via sysfs interface.
sysfs files related to CPU power management:
- maximum CPUs to use. User-configurable, default 4. This is not touched by the Android OS, and will remain in whatever state we set until reboot.
Set this to "1" to make the phone a lot less power-hungry and overheating.
At the cost of performance, of course.
*NOTE: second core will activate sometimes if this is set to "1", but 3rd and 4th cores are disabled for sure.
- minimum number of CPUs to use.
This _is_ touched by the OS, and can not be set reliably.
- time each core spent active. Including 5-th "low-power" core.
cpu: G0 G1 G2 G3 LP
transitions: 26 12 0 0 25
time plugged: 3110 1222 0 0 95122
- another stats interface.
- Max frequency cap for all cores. Default 1500000 (1.5GHz), can be set to any lower value to underclock.
But it is often set by the OS different values (most frequently, back to it's maximum). Maybe, changing this string in libhtc-opt2.so
via hex editor can prevent system from changing it?
- currently active CPU cluster. "LP" for low-power core, "G" for generic (normal) cores.
Can be changed manually, but is also modified by the system at will.
All above values can be changed from root shell via "echo 'value' > /sys/path/to/file"
Maybe, this will come handy to some ROM or CPU-monitoring app developers.
Asus Transformer kernel source
[DEV] Enable 2D GPU rendering in HTC One X & about build.prop tweaks
some findings by phirenz
W/Camera ( 2242): Camera server died!
W/AudioSystem( 660): AudioPolicyService server died!
I/DEBUG ( 1930): debuggerd committing suicide to free the zombie!