[KERNEL] 2.6.32: CPU Vdd levels ("undervolt") sysfs interface

[snq-]

(for devs only)

remember iscaela's "undervolt" hack for the stock - closed source - HTC kernel?
the following quick & dirty kernel mod will allow your users to query and set cpu supply voltages for each frequency through a sysfs interface

the patch is available here: 2.6.32-vddlevels.patch

after applying the patch the "CONFIG_CPU_FREQ_VDD_LEVELS" option will be available in the kernel configuration (set it to 'y')

usage:
query: (output: first column: frequency (kHz), second column: vdd* (mV))

cat /sys/devices/system/cpu/cpu0/cpufreq/vdd_levels
  128000:  950
  245000:  950
  384000:  975
  422400:  975
  460800: 1000
  499200: 1025
  537600: 1025
  576000: 1050
  614400: 1075
  652800: 1100
  691200: 1125
  729600: 1150
  768000: 1175
  806400: 1200
  844800: 1200
  883200: 1225
  921600: 1225
  960000: 1250
  998400: 1275
 1036800: 1275
 1075200: 1275
 1113600: 1300
 1152000: 1300
 1190400: 1300

incrementing/decrementing all levels by a specified amount* (mV):

echo '-25' > /sys/devices/system/cpu/cpu0/cpufreq/vdd_levels
echo '+25' > /sys/devices/system/cpu/cpu0/cpufreq/vdd_levels

adjusting the supply voltage* (second value, mV) at a specific frequency (first value, kHz):

echo '998400 1250' > /sys/devices/system/cpu/cpu0/cpufreq/vdd_levels

*: vdd values must be a multiple of 25 (enforced by the interface; the regulator doesn't accept other values - found out in the hard way)

please note that the values set through this interface will only be written to the acpu table - they will only become effective when the specific frequency is (re)set by cpufreq

i took the input parser from iscaela's code - thanks for it
do not apply this patch if you plan to use avs

to query the constraints of the regulator ("max_microvolts", "min_microvolts") or the voltage currently supplied to the cpu ("microvolts" (uV)):

grep '.' /sys/class/i2c-adapter/i2c-0/0-0048/regulator/regulator.0/*

--
dedicated to the cheeky buggers at #leedroid-roms

 

[LeeDroid]

As always.. Nice work snq-! ​

 

[morcus]

Really nice =)

 

[woooki]

Your kernel is Good~

Your kernel is Good~

Leedroid's Rom is good too.

Thank you.

 

[melethron]

Nice (i think ^^ )

Two Questions:

1. What is "avs"

2. So this makes it possible to change vdd "on the fly" ?
I hadn't issues (reboot/stability) due to undervolting in LeeDroid 2.2a so i can use this to set the vdd levels of the 2.2a Kernel in LeeDroid 2.2e?

 

[snq-]

1. What is "avs"

adaptive voltage scaling ~ cpu supply voltage is actively adjusted based on frequency and temperature

2. So this makes it possible to change vdd "on the fly" ?

yes

I hadn't issues (reboot/stability) due to undervolting in LeeDroid 2.2a so i can use this to set the vdd levels of the 2.2a Kernel in LeeDroid 2.2e?

yes. please note that settings don't persist across reboots, so you might want to create a script under /system/etc/init.d for setting your optimal vdd levels at boot time

 

[melethron]

Nice,

could you post the voltages of the 2.2a Kernel? I didn't find them anymore...

Btw: Smartass Governor is really nice. Highly responsive. Your Kernel rocks.

 

[goochj]

I'd also like to know what voltages the 2.2a kernel was using. I've got the init.d script lowering the voltage by 100mv lower than 2.2e stock voltages, How low can I go!

 

[snq-]

could you post the voltages of the 2.2a Kernel?

I'd also like to know what voltages the 2.2a kernel was using.

the only difference regarding voltages: [email protected] (2.2a) vs [email protected] (2.2e)

 

[TheGhost1233]

Oke i have been doing some searching about the hole undervolting thing. What i found was that undervolting has no real risks unlike overclocking, what i read is that when you go to low your pc/phone(found mostly pc stuff) will freeze up. Since this interface will reset the voltages after a reboot there shouldn't be a real problem i believe.
However before i go and change my voltages i would like to know if this is right and there is no realistic risk involved with undervolting, and i won't damage my hardware.

Thanks

 

[mr.r9]

^Undervolting will result in instability if it's extreme with no hardware faults. On the other hand, Over-volting, if extreme, will result in hardware faults.
In any case, there are a few Kerenals you can try without needing this patch because it is aimed at developers & not users.

 

[tyween]

Can someone post an init.d script for lowering vdd_levels? I am having a problem writing one.

 

[RedWave31]

UP!

Hello all,

I'd like to mess with my settings too, and need a how-to

Any help appreciated!

Thanks

 

[RedWave31]

For those who are wondering, Hastarin has posted THE UNDERVOLT SCRIPT at his kernel page, u can edit the script as wanted!!!

 

[danarama]

I know this is for devs, but has anyone successfully implemented this (or similar) as an end-user?

I would definitely like to try

 

[silent_silver]

"the patch is available here: 2.6.32-vddlevels.patch"

how do i apply this patch? and how do i create a script to make it work after reboot ?

 

[funkatiko]

For those who are wondering, Hastarin has posted THE UNDERVOLT SCRIPT at his kernel page, u can edit the script as wanted!!!

Where?? I´ve been searching for his webpage and didn´t find it....

 

[voided]

Missing clock speed after apply

Hi

Thank you for providing the codes for undervolt but I have missing clockspeed after i tried to combine you patch with MJ S10.4 kernel.

Hope you can advise. Thanks in advance

 

[jukyO]

Where?? I´ve been searching for his webpage and didn´t find it....

There you go:

http://forum.xda-developers.com/showthread.php?t=857929

 

[jukyO]

"the patch is available here: 2.6.32-vddlevels.patch"

how do i apply this patch? and how do i create a script to make it work after reboot ?

Really, how to apply it?