[Note Edge General] AlaskaLinuxUser:
Post #9. kernel - How to Overclock/Undervolt.

Post #9. kernel - How to Overclock/Undervolt.

Overclock an apq8084 Samsung Galaxy Note Edge!

You can see the commit on github here:

https://github.com/alaskalinuxuser/...mmit/9bb23d0d9cc805bf7e1b8e3fe829fcbb0542af31

In my continuing quest to make a better kernel for the Samsung Galaxy Note Edge (TBLTE, N915T), I decided to tackle overclocking the kernel. There are already some overclocked kernels out there, but I decided to do something slightly different with mine. The distinguishing feature of my overclocked kernel is that it doesn't use any more power than it did before, and to God be the glory, it worked!

I also feel that when you overclock a chip, you are increasing the rate of failure, and the induced heat load. So I like to keep my overclocking light, less than 10% of the overall capacity that the chip was designed for. It is my hope that this will reduce wear and tear on the device while still providing superior performance.

Editing the tables for this chip was a lot simpler than for other chips I have worked on.

It all took place within the kernel/samsung/tblte/arch/arm/boot/dts/qcom/apq8084.dtsi file. Here is how it used to look:

.............EDITED FOR SPACE................
/* 2.7GHz RC1 */
qcom,speed2-pvs0-bin-v1 =
< 0 0 0 >,
< 300000000 810000 76 >,
< 345600000 820000 88 >,
.............EDITED FOR SPACE................
< 2496000000 1120000 813 >,
< 2572800000 1135000 849 >,
< 2649600000 1150000 886 >;

And here was my change, from 2649600000 to 2688000000:

.............EDITED FOR SPACE................
/* 2.7GHz RC1 */
qcom,speed2-pvs0-bin-v1 =
< 0 0 0 >,
< 300000000 810000 76 >,
< 345600000 820000 88 >,
.............EDITED FOR SPACE................
< 2496000000 1120000 813 >,
< 2572800000 1135000 849 >,
< 2688000000 1150000 886 >;

That's right, I only made a 39MHz change. I feel this was appropriate to keep the device cool and continue to use the same voltages. So it is essentially a 39MHz boost with no noticable consequences. Of course, I had to do the above to each speed and pvs table in that file.

Then, I needed to edit this portion:

.............EDITED FOR SPACE................
qcom,msm-cpufreq@0 {
reg = <0 4>;
compatible = "qcom,msm-cpufreq";
qcom,cpu-mem-ports = <1 512>;

qcom,cpufreq-table =
< 300000 300000 1144 800 >,
< 422400 422400 2288 800 >,
.............EDITED FOR SPACE................
< 2572800 1728000 16250 10101 >,
< 2649600 1728000 16250 10101 >;
.............EDITED FOR SPACE................

To this:

.............EDITED FOR SPACE................
qcom,msm-cpufreq@0 {
reg = <0 4>;
compatible = "qcom,msm-cpufreq";
qcom,cpu-mem-ports = <1 512>;

qcom,cpufreq-table =
< 300000 300000 1144 800 >,
< 422400 422400 2288 800 >,
.............EDITED FOR SPACE................
< 2572800 1728000 16250 10101 >,
< 2688000 1728000 16250 10101 >;
.............EDITED FOR SPACE................

It actually was the only time I have overclocked a kernel on the second try. Don't think too highly of me, though, I spent hours reviewing kernel edits for overclocking by various other kernel developers on GitHub. If you are looking to do the same, you should spend some time looking at working code for others, and then make your own tables.

If you try this on your own, you may have multiple tries where the phone will not even boot, or crashes while you use it, so be careful, make small changes, and be courageous, because this is usually not a simple one stop process.

If you were to compare my tables with everyone elses, you would see that I have done it differently than my contemporaries, even though we reached similar, or in some cases, identical results. I like to keep the code clean, short, and sweet. Often when overclocking, most kernel developers will add more lines to the tables. I have found that while that may be the best to maximize use, my method is much simpler and easy to implement, as well as follow, and that is what Linux should be all about, keeping it simple. It also makes it easier for "stock" kernel hot-plug controllers like MPDecision.

Under-volt a Samsung Galaxy Note Edge:

So, back to our ealier example of the overclocked chip, now we want to change the voltage. Doing that is easy, getting viable, stable, working results is much harder. Consider our code from the kernel/samsung/tblte/arch/arm/boot/dts/qcom/apq8084.dtsi file:

.............EDITED FOR SPACE................
/* 2.7GHz RC1 */
qcom,speed2-pvs0-bin-v1 =
< 0 0 0 >,
< 300000000 810000 76 >,
< 345600000 820000 88 >,
.............EDITED FOR SPACE................
< 2496000000 1120000 813 >,
< 2572800000 1135000 849 >,
< 2649600000 1150000 886 >;

To change the voltage, one only has to edit these multiple pvs trees.

Consider this line:

< 2572800000 1135000 849 >

It means:

< Frequency Voltage Amperage (? or cycles) >

So, in the above table, the 2572 MHz frequency uses 113.5 mv.

And, in the above table, the 2649 MHz frequency uses 115 mv.

So, to under-volt you could edit it like so:

< 2572800000 1120000 849 >,
< 2649600000 1135000 886 >;

This would cut down the voltage used on each of these frequencies. The problem is, however, if you go too low, you may cause the kernel to crash. Notice that in my overclocked kernel, I under-volted it to the same as the 2649 MHz frequency, even though I am using it at 2688 MHz. So, use with caution, and have fun making adjustments! I recommend only small changes or even only one change at a time.