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Change CPU clock frequency of am57xx-evm using device tree

Govindaraji Sivanantham
Intellectual 880 points

we need to change the CPU clock frequency of am57xx-evm to maximum 1 GHz using device tree file. so that scaling_max_frequency should be set to 1 GHz.

Please let us know how to change it in device tree.

  • 0
    TI__Guru** 116100 points
    You can check the current frequency through CPU FREQ governor.
    /sys/devices/system/cpu/cpu0/cpufreq/

    I think , you need to change the dts file like below for 1GHz in appropriate AM57xx dts file.

    operating-points = <
    /* kHz uV */
    1000000 1060000
    >;
  • 0
    TI__Guru**** 170625 points
    Hi Govindaraji,

    In addition, the DTS file you need to change is:
    ti-processor-sdk-linux-am57xx-evm-03.00.00.04/board-support/linux-4.4.12/arch/arm/boot/dts/dra72x.dtsi

    See also the below wiki:
    processors.wiki.ti.com/.../Linux_Core_Power_Management_User's_Guide_(v4.1)

    Regards,
    Pavel
  • 0 in reply to Pavel Botev
    Intellectual 880 points
    In both dra72x.dtsi and dra74x.dtsi only one operating point mentioned is:
    operating-points = <
    /* kHz uV */
    1000000 1060000
    >;

    That means the device maximum operating frequency is 1000000 kHz?
    But still I see maximum_scaling_frequency is set to 1500000 KHz.

    And if the CPU load is less than 1GHz, will the device scale down the clock frequency?

    We need to achieve the Maximum frequency to 1GHz and if the load is less, the frequency should be scale down.

    How can we achieve this?
  • 0 in reply to Govindaraji Sivanantham
    TI__Guru**** 170625 points
    Hello,

    I mean the below file:

    ti-processor-sdk-linux-am57xx-evm-03.00.00.04/board-support/linux-4.4.12/arch/arm/boot/dts/dra7.dtsi

    cpu0_opp_table: opp_table0 {
    compatible = "operating-points-v2";
    opp-shared;

    opp_nom@1000000000 {
    opp-hz = /bits/ 64 <1000000000>;
    opp-microvolt = <1060000 850000 1150000>;
    opp-supported-hw = <0xFF 0x01>;
    opp-suspend;
    };

    opp_od@1176000000 {
    opp-hz = /bits/ 64 <1176000000>;
    opp-microvolt = <1160000 885000 1160000>;
    opp-supported-hw = <0xFF 0x02>;
    };

    opp_high@1500000000 {
    opp-hz = /bits/ 64 <1500000000>;
    opp-microvolt = <1210000 950000 1250000>;
    opp-supported-hw = <0xFF 0x04>;
    };
    };