[Galaxy S II I9100G Android Development] fuss132:
FAQ:

How do i change voltage?

Use the latest version of setcpu, leantweaks, cputuner, or your ROM's built-in tools.

Do i need to wipe dalvik/cache?

In general there's no need, but it doesn't hurt so if you have time go ahead. Posted Image I don't wipe.

What's the variable on the GPU OC?

The kernels GPU is now set to stock 307Mhz by default. You can adjust that by using Variable GPU OC (see a separate FAQ entry below).

When you go from say 307 to 512Mhz, you will not experience near double performance increase. Due to the factors outside the GPU module (ie. memory bandwidth limitation), you can't truly OC the GPU. In fact, most people can't tell the difference between 307, 384 and 512. Nenamark2 will roughly give you the following scores: 307/25fps, 384/28fps, and 512/31fps.

Some of you have seen the note from Colin, the Google kernel engineer, not to OC the GPU because using the OV_UV voltage slot will drain the battery. Greenblob kernel uses the same voltage for both OV and OV_UV slots. So there's no danger of battery drain there.

My phone doesn't seem to be deep-sleeping, what gives?

(assuming you checked in the right place like cpuspy) In terms of deep-sleep, there's not a whole lot going on in the kernel. It works or it doesn't - and I can assure you that I test every release (well almost every release) for deep-sleep before I release.

19 out of 20 times it's either 1) some sort of background process that's preventing your phone from going into deepsleep, or 2) something's misconfigured in your ROM, or both. Also connecting to USB will prevent phone from going into deepsleep.

I'm having unusual battery drain - help!

First of all, our i9100g (AS every Smartphone ^^) has very poor battery life while in active use. It's downright horrible while screen is on - screen is definitely the main culprit and there's not a whole lot I can do about that.

Custom undervolting can help or can hurt. This is mainly due to SmartReflex (class1.5) which auto-calibrates the ideal voltages for you. In fact, with SR you don't really need to use the custom undervolting feature for frequencies other than the 2 lowest. It does a great job calibrating higher frequencies. I personally don't touch it.

The "notrim" versions are an exception because I had to disable SR1.5 for the trim override to work. There's no auto-calibration going on there. Feel free to mess with custom undervolting on the notrim versions.

Now, if you've already accepted the horrible battery life while screen is on, but have questions about battery drain while idle - read the next question.

I'm having unusual battery drain while screen is off, or phone is sleeping - help!

First, let's find out if you're phone is going into deep-sleep. Install CPUSpy, unplug phone, turn off screen, and leave the phone alone for 5-10min. Turn the screen back on, launch CPUSpy, and see if you see an active entry for Deep Sleep. If so congratulations - read on.

If you've determined that your phone is not entering deepsleep by using the above method, read my entry above that says "My phone doesn't seem to be deep-sleeping". I've heard that removing SDM.apk helps as well as rebooting the phone. Also try turning your bluetooth on and off, and launching camera app and closing it.

If you've determined that your phone is entering deepsleep fine but still feel like battery drains, read the next question.

I'm having unusual battery drain while phone is in deep-sleep - help!

First make sure you are absolutely positive that deep sleep is working (read the previous question).

While on my kernel *and* connected to Wifi, you shouldn't drain more than 2% battery per hour *average* while in deep sleep (based on 5-8 hour continuous deep sleep). With wifi turned-off, my guess is probably no more than 3-6% per hour, depending on signal strength.

tip 1: If above is not happening for you, first charge the phone all the way and reboot. Let things settle a bit - give it a day or so. If you're using Battery Monitor Widget (which is not accurate for gnex), things should eventually settle between -2mA and -60mA per sample.

tip 2: Install BetterBatteryStats and look at which wakelocks dominate. Google search for names of the wakelocks to see how you can fix them.

tip 3: http://checkthis.com/d87t

If nothing seems to help, you can try the "notrim" version, but stick to speeds between 350 and 1350 (don't use OC slots). The notrim version has SR1.5 disabled which could help for those of you with drain issues on my other kernels.

What is SmartReflex?

SmartReflex performs continuous dynamic voltage scaling around the nominal operating point voltage according to silicon characteristics and operating conditions.

My stable and experimental builds will have SR Class 1.5 enabled by default.

You can disable SR via sysfs

How do I use Variable GPU OC?

You can use Lean Tweaks by Jake, or use the built-in "oc" script. Both leantweaks and my oc script will create an init.d script so the setting sticks at boot. My "checkt" script will also show the current GPU max speed. Note that 512MHz will probably not work for everyone.

307Mhz (stock) is set default by the kernel.

Open Terminal, and type for stock speed of 307Mhz: oc gpu 0

for 384MHz: oc gpu 1

for 512Mhz: oc gpu 2

FAQ partly taken from leankernel! I changed the important parts for us! Thanks to them! http://xdaforums.com/showthread.php?t=1790675​