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Frequency set to 1 GHz

lyf sci
Genius 3720 points
Other Parts Discussed in Thread: AM3359

Hi Experts,

How to set the processor frequency to 1 GHz in the AM335x starter kit ?


The existing power governor option provides the options like 275 MHz to 720 MHz. Is it possible to set 1GHz from user space ?

  • 0
    TI__Guru**** 161600 points

    Hi,

    You can't set MPU frequency to 1GHz.
    Highest possible MPU OPP is OPP Turbo, which allows 720MHz, see AM335x datasheet: http://www.ti.com/general/docs/lit/getliterature.tsp?genericPartNumber=am3359&fileType=pdf

    Some devices support OPP Nitro, i.e. see Table 5-7 VDD_MPU_OPP for ZCZ Package with Device Revision Code "A" or Newer. But if this governor is not included in sysfs, you will have to modify the kernel.  See http://processors.wiki.ti.com/index.php/Linux_Core_Power_Management_User%27s_Guide for more details.

    Also beware, that manually setting the device to highest possible OPP reduces its life span. It is best to let the kernel automatically transition from higher to lower OPP and vice versa, depending on CPU load .

    Best Regards,

    Yordan

  • 0 in reply to Yordan Kovachev
    Genius 3720 points

    Hi Yordan,

    Thanks for the reply.

    Yordan Kovachev said:
    It is best to let the kernel automatically transition from higher to lower OPP and vice versa, depending on CPU load .

    Consider I am increasing the CPU load by invoking certain applications.

    Is there any mechanism to read the transition in  frequency by reading some registers or either sysfiles when the frequency governor is set to work as you specified  above ?



  • 0 in reply to lyf sci
    TI__Guru**** 161600 points

    Hi,

    You can monitor current frequency of CPU. I.e you could issue:
    watch -n 1  cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq > log.txt

    This monitors the current CPU frequency every 1 sec.

    You can also monitor

     - time spent in each power state (OPP):

    cat  /sys/devices/system/cpu/cpu0/cpufreq/stats/time_in_state

     - total transitions:
    cat  /sys/devices/system/cpu/cpu0/cpufreq/stats/total_trans

     - transition table:
    cat  /sys/devices/system/cpu/cpu0/cpufreq/stats/trans_table

    Just FYI, as I said, you could "force" your device to go up to 1GHz. You need to check the marking of your chip, if it is ZCZ Package with Device Revision Code "A" or Newer you can go up to 1GHz (OPP120 - Nitro), following the steps from Linux_Core_Power_Management_User_Guide (link in my previous post).

    Best Regards,

    Yordan

  • 0 in reply to Yordan Kovachev
    Genius 3720 points

    Hi Yordan,

    Thanks for your detailed response.