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TDA4VM: Cortex A72 frequency control under Linux

Francois Charlot
Mastermind 23137 points
Part Number: TDA4VM

Hello,

Is there any way to read and control the A72 operating frequency under Linux (J721E EVM)? On DRA7xx, we could cat and echo to /sys/devices/system/cpu/cpu0/cpufreq. Is the same or a similar mechanism supported in the TDA4VM SDK?

Thank you.


Best regards,
François.

  • 0
    TI__Guru*** 131050 points

    Hi Francois,

    No support for DVFS on TDA4VM through Linux. However we have k3conf tool on SDK.
    With that you can try to alter frequency of A72.

    Set: PLL8_SS_CTRL Register bit[0] to 1.
    devmem2 0x688040 w 0x80000001
    •We can now set 1GHz, 1.2GHz & can see the output of k3conf with A72 frequency set to respective values.

    k3conf set clock 202 2 1000000000
    •|-----------------------------------------------------------------------------------------|
    •| Device ID | Clock ID | Clock Name                   | Status         | Clock Frequency |
    •|-----------------------------------------------------------------------------------------|
    •|   202     |     2   | DEV_A72SS0_CORE0_ARM_CLK_CLK | CLK_STATE_READY | 1000000000     |
     

    So basically dynamic frequency scaling can be achieved as there is no PMIC control from A72.

    Hope you can resolve the issue.

    Best Regards,
    Keerthy
  • 0 in reply to Keerthy J
    TI__Mastermind 23137 points

    Hi Keerthy,

    Thank you. The TDA4VM datasheet says that these cores may operate at up to 1.8 GHz. Is this possible on the EVM? You just mention 1.0 and 1.2 GHz... What is the default speed in our Linux SDK?


    Best regards,
    François.

  • 0 in reply to Francois Charlot
    TI__Guru*** 131050 points

    Hi François,

    It boots at 2GHz.

    You can try 1.0, 1.2, 1.5, 1,8 using k3conf and that should work.

    Default boot frequency can be checked using k3conf as well:

    k3conf dump clock 202
    Hope we can resolve this thread.

    - Keerthy

  • 0 in reply to Keerthy J
    TI__Mastermind 23137 points

    Hi Keerthy,

    Thank you very much for confirming. I do not have additional questions.


    Best regards,
    François.