User:TheSame/nokia-n900 notes/Overclocking on pmOS
Introduction
This manual was created based on a similar manual for Maemo Leste and adapted by the pmOS feature.
After this procedure there will be two kernel images in /boot partition: normal and overclocked. If you want, you can always return to the normal kernel.
The emmc of my N900 has Maemo Fremantle installed with u-boot installed. This manual is adapted to this situation.
All manipulations, except those related to setting up u-boot, can be done directly in pmOS.
This overclock allows you to use a frequency range of 250Mhz to 850Mhz.
The setup process in Maemo Fremantle
In this step we will create a boot entry for u-boot in Maemo Fremantle.
Creating a boot record for u-boot
1. Create a new entry for u-boot:
/etc/bootmenu.d/15-pmos-overclock.item
ITEM_NAME="postmarketOS <Overclock>" ITEM_SCRIPT="bootX.scr" ITEM_DEVICE="${EXT_CARD}p1" ITEM_FSTYPE="ext2"
2. Run u-boot-update-bootmenu to add a new entry.
The setup process in pmOS
At this point, we modify the existing kernel and add a new system startup script.
The following commands will create some files. I will create them on the /root path, but you can put them wherever you want. All commands below will be done as root.
Creating a boot.scr file
1. Create a boot.cmd text file the way you want:
/root/boot.cmd
setenv mmcnum 0 setenv mmcpart 1 setenv mmctype ext2 setenv setup_omap_atag 1 setenv bootargs init=/init.sh rw console=tty0 console=ttyS2 PMOS_NO_OUTPUT_REDIRECT PMOS_FORCE_PARTITION_RESIZE setenv mmckernfile /uImageX setenv mmcinitrdfile /uInitrd setenv mmcscriptfile echo Loading initramfs run initrdload Loading kernel run kernload echo Booting kernel run kerninitrdboot
2. Create bootX.scr file and put it in /boot:
# mkimage -c none -A arm -T script -d /root/boot.cmd /boot/bootX.scr
Creating a modified kernel
1. Get omap3-n900.dtb:
# cp /boot/dtbs/omap3-n900.dtb /root
2. Get .dts file. When you run this command you will see a lot of messages, you can ignore them. You may need to install dependencies dtc:
# dtc -I dtb -O dts /root/omap3-n900.dtb -o /root/omap3-n900.dts
# chmod +w /root/omap3-n900.dts
3. Modify omap3-n900.dts and add new frequencies. To do this, find the opp-table section and edit it according to the example below:
opp-table {
compatible = "operating-points-v2-ti-cpu";
syscon = < 0x05 >;
phandle = < 0x03 >;
opp1-250000000 {
opp-hz = < 0x00 0xee6b280 >;
opp-microvolt = < 0xee098 0xee098 0xee098 >;
opp-supported-hw = < 0xffffffff 0x03 >;
};
opp2-500000000 {
opp-hz = < 0x00 0x1dcd6500 >;
opp-microvolt = < 0x106738 0x106738 0x106738 >;
opp-supported-hw = < 0xffffffff 0x03 >;
opp-suspend;
};
opp3-600000000 {
opp-hz = < 0x00 0x23c34600 >;
opp-microvolt = < 0x124f80 0x124f80 0x124f80 >;
opp-supported-hw = < 0xffffffff 0x03 >;
};
opp4-720000000 {
opp-hz = < 0x00 0x2aea5400 >;
opp-microvolt = < 0x124f80 0x124f80 0x124f80 >;
opp-supported-hw = < 0xffffffff 0x03 >;
};
opp5-850000000 {
opp-hz = < 0x00 0x32a9f880 >;
opp-microvolt = < 0x149970 0x149970 0x149970 >;
opp-supported-hw = < 0xffffffffff 0x03 >;
};
opp6-720000000 {
opp-hz = < 0x00 0x2aea5400 >;
opp-microvolt = < 0x149970 0x149970 0x149970 >;
opp-supported-hw = < 0xffffffffff 0x02 >;
turbo-mode;
};
};
4. Generating a new .dtb file:
# rm /root/omap3-n900.dtb
# dtc -I dts -O dtb /root/omap3-n900.dts -o /root/omap3-n900.dtb
5. Create a zImage_dtb:
# cat /boot/vmlinuz /root/omap3-n900.dtb > /tmp/zImage_dtb
6. Create and put in /boot a new uImageX:
# mkimage -A arm -O linux -T kernel -C none -a 80008000 -e 80008000 -d /tmp/zImage_dtb /boot/uImageX
Checking the success of the operation
After completing all the steps, reboot pmOS using the new item in the u-boot that we added.
You can use cpufrequtils to check if new frequencies have been added. The result should be about the same as below.
nokia-n900:~$ cpufreq-info
cpufrequtils 008: cpufreq-info (C) Dominik Brodowski 2004-2009
Please report bugs and errors to cpufreq@vger.kernel.org.
analyzing CPU 0:
driver: cpufreq-dt
CPUs that run at the same hardware frequency: 0
CPUs which frequency must be coordinated programmatically: 0
maximum transition delay: 300 us.
hardware limitations: 250 MHz - 850 MHz
available frequency steps: 250 MHz, 500 MHz, 600 MHz, 720 MHz, 850 MHz.
available cpufreq controls: conservative, on demand, user space, power saving, performance
current policy: frequency must be within 250 MHz and 850 MHz.
The "conservative" controller can decide what speed to use
in this range.
The current CPU frequency is 850 MHz.
If everything is correct, the operation is successful!
You can change the mode of the core for more powersafe:
# cpufreq-set -c 0 -g conservative
 |
WARNING: Always use the stock pmOS kernel before updating the kernel. The new uImageX must be re-created and the old uImageX must be removed after each kernel update. |
More fine-tuning of core frequency and voltages
You can try to raise the core frequency above 850 MHz by editing the opp-table to your liking. It all depends on how lucky you are with your SoC. The voltage and frequency can be edited to get the desired result.
|
WARNING: Be careful about increasing the voltages for the SoC. I am not responsible for damaged devices, but only passing on my experience. |
To increase the core frequency, edit the variable opp-hz according to your wishes. The values must be in HEX format. Example: 0x32a9f880 = 850000000.
To increase the core volts, edit all 3 numbers in the opp-microvolt variable to your liking. The values must be in HEX format. Example: 0x149970 = 1350000.
On my device I was able to raise the frequency to 890Mhz without raising the voltage. When I raised the voltage above 1.37V, I lost stability of the system. The system also lost stability when I raised the frequency to 900MHz. According to the information I found, no one has raised the voltage above 1.5V (in Maemo Fremantle).
My final configuration for oop5 (I repeat, it may not work for you):
opp5-890000000 {
opp-hz = < 0x00 0x350c5280 >;
opp-microvolt = < 0x149970 0x149970 0x149970 >;
opp-supported-hw = < 0xffffffffff 0x03 >;
};
Useful Links
- A superficial description of the opp-table syntax;