Develop Bugs

[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:
/sys/kernel/debug/tegra_hotplug/max_cpus - 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.
/sys/kernel/debug/tegra_hotplug/min_cpus - minimum number of CPUs to use.
This _is_ touched by the OS, and can not be set reliably.
/sys/kernel/debug/tegra_hotplug/stats - time each core spent active. Including 5-th "low-power" core.
e.g.:
Code:
cpu: G0 G1 G2 G3 LP
transitions: 26 12 0 0 25
time plugged: 3110 1222 0 0 95122
time-stamp: 4296183486
/sys/kernel/debug/cpuidle/lp2 - another stats interface.
/sys/module/cpu_tegra/parameters/cpu_user_cap - 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?
/sys/kernel/cluster/active - 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.
References:
Asus Transformer kernel source
[DEV] Enable 2D GPU rendering in HTC One X & about build.prop tweaks
some findings by phirenz

is there any way to request more use of the companion core?

In case anyone's wondering, I just found out that /sys/kernel/cluster/active must be opened as root even for reading; opening the file as any other user will not succeed.
The other files seem to allow reading as a standard user, however.

It woulod be great is someone created an app for setting number of CPUs. It is useful sometimes to set it to 1 when you are traveling and want to get max possible battery.
It would be even better if it was possible to disable all 4 cores and force system to use LP core only. It would be brilliant max power saving mode.

I've modified OS Monitor to support Tegra 3's stuff (temperature, number of cores and determining whether it is low power/general CPU in use) and my experience is that there's no or very little battery gains to be had because the other 3 cores are off most of the time anyway (when idle)
I'm using stock 1.28. The low power core doesn't seem to like being activated for more than a few seconds at a time, too.

I've modified OS Monitor to support Tegra 3's stuff
Click to expand...
Click to collapse
Can u share the apk here...xD???

thanks to the OP.....I don't have a One X but this info helped me to force all 4 cores of my Asus TF300T go online and offline as i wish.

schriss said:
It woulod be great is someone created an app for setting number of CPUs. It is useful sometimes to set it to 1 when you are traveling and want to get max possible battery.
It would be even better if it was possible to disable all 4 cores and force system to use LP core only. It would be brilliant max power saving mode.
Click to expand...
Click to collapse
use core control or francos kernel updater works for every custom kernel also stock kernel and you can choose how many cores...but battery life is not better with deactivated cores and soemetimes even worser -.-

I used to be able to do this, but now I'm using n3o kernel and I can't find the tegra_hotplug folder inside sys/kernel/debug. Help?

joeystar said:
I used to be able to do this, but now I'm using n3o kernel and I can't find the tegra_hotplug folder inside sys/kernel/debug. Help?
Click to expand...
Click to collapse
Man ask this in kernel thread not here....-.-
Sent from my HTC One X using xda app-developers app

5\6 cores is stopped

Hey everyone,
Recently my device is very slow. I downloaded the app CPU-Z and my surprise that 5 of 6 cores are not working.
Notably, the device is not on battery saving mode.
H815 Android 5.1 no rooted.
Does anyone know what the problem is and how to fix it? Because it is nearly impossible to use the device.
Thanks

Cores 5 and 6 is for Big Cpu and they will enable only when it need
If you are sure that it not work try Download Kernel adiutor then in cpu settings click on the checkbox cpu cores
Sent from my Xperia SP

Does my P-600's all cores working?

Hello, in my device running Exynos 5420. This cpu have 8 cores. Why when I running cpu-z app it shows only 4 cores - 0,1,2,3 cores. Where another 4 (Cortex A7)?
I attached screenshot.
https://www.dropbox.com/s/npshqo2wtnlqomm/Screenshot_2016-12-23-17-12-38.jpg?dl=0
Thanks for advices.

Sunrise2000 said:
Hello, in my device running Exynos 5420. This cpu have 8 cores. Why when I running cpu-z app it shows only 4 cores - 0,1,2,3 cores. Where another 4 (Cortex A7)?
I attached screenshot.
https://www.dropbox.com/s/npshqo2wtnlqomm/Screenshot_2016-12-23-17-12-38.jpg?dl=0
Thanks for advices.
Click to expand...
Click to collapse
It's all the same everywhere ... I guess that's because KK and LL don't have the ability to use and control 8 cores at the same time ... The A7 small cores actually start working when system is doing demanding tasks ... As a Kernel Dev , I can confirm that the appropriate Drivers are implemented for both A7 and A15 Processors ... So , It should be just that the current Android Arch is not that compatible with 8 Core Control ... I guess It was said that in Nougat , the New arch does support full 8 Core control ... But , So far I haven't faced such features in related threads and i don't want to make you think that it would be GREAT to control 8 cores because currently TW's source does it by itself ... I hope it was helpful to you ...
With Best Wishes
Hitman1376​

CPU scheduler issue (Lineage 14.1 nightly).

Hello everyone!
I have samsung galaxy A520F with official lineage 14.1 (version 14.1-20180509-NIGHTLY-a5y17lte) installed.
I facing strange cpu scheduler behavior now:
1. Scheduler never uses more than 4 cores, although phone has 8 equal cortex-A53 cores.
2. Scheduler never uses less than 4 cores, even at light loads(4-10%)
3. Scheduler sets equal cores frequencies for all 4 cores.
On the stock OS everything was as expected, at light load there were 1 core active at small frequency, and at high load all 8 cores was active.
Screenshots to be added.
Thanks!

You better post there:
https://forum.xda-developers.com/samsung-a-series-2017/development/rom-lineageos-14-1-alpha-t3654935

Why Cpu All Core Working Without Use Any App?

Cpu Every Core Working Without Use Any App in Recent List

It shows 633Mhz for me (first four cores)
which rom you are on ?
however background processes of Android do take cpu usage

YasuHamed said:
It shows 633Mhz for me (first four cores)
which rom you are on ?
however background processes of Android do take cpu usage
Click to expand...
Click to collapse
I Think Other Core Should Stop When Not Use Any App in Recent

I does not seem to work like that. I have never seen my Redmi having a single idle CPU core
Sent from my whyred using XDA Labs

RupeshRN said:
I Think Other Core Should Stop When Not Use Any App in Recent
Click to expand...
Click to collapse
You think wrong

RupeshRN said:
I Think Other Core Should Stop When Not Use Any App in Recent
Click to expand...
Click to collapse
stock min freq is little 633 mhz big 1130mjz
underclocked can go to 300mhz both big and little.
you mean a hotplug.. when not in use all cores off then whn input turn on... unfortunatelly theres no hotplug for 636.. as they say in kernel settings balme qualcomm