✎ odroid-c2:application_note:software:set_cpu_freq [ODROID Wiki]

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====== How to set max cpu frequency and cores ======

<WRAP round important>
  * Ubuntu : Available with 3.14.77-80 (Sep 8, 2016) or higher version
  * Android : Available with Android v2.2 or higher version
</WRAP>

For further information, you can refer to the following forum thread.

http://forum.odroid.com/viewtopic.php?f=141&t=23044
===== How to set max cpu frequency =====

Here are the available cpu frequency sets and you can set one of them as max. cpu frequency using boot.ini

== The available list of cpu frequency set ==

Here are the common sets we recommend under normal conditions.

|  frequency  |  notation on boot.ini  |
|  1.656 GHz  |  "1656"  |
|  1.536 GHz  |  "1536"  |
|  1.296 GHz  |  "1296"  |
|  1 GHz  |  "1000"  |
|  500 MHz  |  "500"  |
|  250 MHz  |  "250"  |
|  100 MHz  |  "100"  |

There are some advanced frequency sets you can try below.

The following sets are unstable with 2 or more cpu-cores so, you should adjust cpu cores as described the next section.

|  frequency  |  notation on boot.ini  |  note  |
|  1.680 GHz  |  "1680"   | booting OK with 4 cores / recommend 3 cores for heavy load test  |  
|  1.752 GHz  |  "1752"   | booting OK with 4 cores / recommend 2 cores for heavy load test  |
|  1.896 GHz  |  "1896"  | booting OK with 1~3 cores / recommend running with a single core  |
|  1.920 GHz  |  "1920"  | booting OK with 1 or 2 cores / recommend running with a single core  |
|  1.944 GHz  |  "1944"  | booting OK with a single core but unstable |
|  2.016 GHz  |  "2016"  | extremely unstable  |

== setting boot.ini ==

Please modify **max_freq ** based on the aforementioned frequency table. The unit of max_freq in boot.ini is MHz.

If you don't set max_freq in bootargs or the setting value is wrong one which doesn't exist in frequency table, max_freq will be set as "1.536GHz" by default.

<code ini>
### boot.ini

# max cpu frequency in dvfs table / in MHz unit
# setenv max_freq "2016"  # 2.016GHz
# setenv max_freq "1944"  # 1.944GHz
# setenv max_freq "1920"  # 1.920GHz
# setenv max_freq "1896"  # 1.896GHz
# setenv max_freq "1752"  # 1.752GHz
# setenv max_freq "1680"  # 1.680GHz
# setenv max_freq "1656"  # 1.656GHz
setenv max_freq "1536"  # 1.536GHz

# Boot Arguments
# add max_freq in bootargs
setenv bootargs "root=UUID=e139ce78-9841-40fe-8823-96a304a09859 rootwait ro ${condev} no_console_suspend max_freq=${max_freq} hdmimode=${m} ${comde} m_bpp=${m_bpp} vout=${vout} fsck.repair=yes net.ifnames=0 elevator=noop disablehpd=${hpd}"
</code>

After setting it, then be sure you do reboot.

You can check the frequency list as following. 

ex) setenv max_freq "1656"
<code bash target>
root@odroid64:~# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies 
100000 250000 500000 1000000 1296000 1536000 1656000 
</code>

===== How to set the number of cpu cores  =====

Also, you can set cpu-cores you want to activate using boot.ini

The available range is "1" to "4"

== setting boot.ini ==

<code ini>
### boot.ini

# max cpu-cores
# setenv maxcpus "1"
# setenv maxcpus "2"
# setenv maxcpus "3"
setenv maxcpus "4"

# Boot Arguments
# add maxcpus in bootargs
setenv bootargs "root=UUID=e139ce78-9841-40fe-8823-96a304a09859 rootwait ro ${condev} no_console_suspend max_freq=${max_freq} maxcpus=${maxcpus} hdmimode=${m} ${comde} m_bpp=${m_bpp} vout=${vout} fsck.repair=yes net.ifnames=0 elevator=noop disablehpd=${hpd}"
</code>

After setting it, then please be sure you do reboot.

You can check the activated cpu cores as following.

ex) setenv maxcpus "2"
<code bash target>
root@odroid64:~# cat /sys/devices/system/cpu/online 
0-1
root@odroid64:~# cat /sys/devices/system/cpu/offline                                                                       
2-3
</code>

<code bash target>
root@odroid64:~# cat /proc/cpuinfo 
processor       : 0
BogoMIPS        : 2.00
Features        : fp asimd crc32
CPU implementer : 0x41
CPU architecture: 8
CPU variant     : 0x0
CPU part        : 0xd03
CPU revision    : 4

processor       : 1
BogoMIPS        : 2.00
Features        : fp asimd crc32
CPU implementer : 0x41
CPU architecture: 8
CPU variant     : 0x0
CPU part        : 0xd03
CPU revision    : 4

Hardware        : ODROID-C2
</code>