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AM3354: Cpufreq

Nancy Wang
Expert 8210 points
Part Number: AM3354

Hi,

AM3354 MAX cpu frequency:800MHZ

The customer used latest RT-linux SDK, and he used default kernel configuration. What's the default cpufreq. Where is the configuration code?

The option cpu frequency scaling haven't been selected in default menuconfig.

  • 0
    TI__Guru**** 170625 points

    Hi Nancy,

    CPUFreq is enabled by default in PSDK Linux, and NOT enabled by default in PSDK Linux-RT. You can compare below files:

    ti-processor-sdk-linux-am335x-evm-06.00.00.07/board-support/linux-4.19.38/arch/arm/configs/tisdk_am335x-evm_defconfig

    ti-processor-sdk-linux-rt-am335x-evm-06.00.00.07/board-support/linux-rt-4.19.38/arch/arm/configs/tisdk_am335x-evm-rt_defconfig


    To enable CPUFreq in linux-rt, follow the below user guide steps:

    Dynamic Voltage and Frequency Scaling(MPU aka CPUFREQ)

    Kernel Configuration Options


    Regards,
    Pavel

  • 0 in reply to Pavel Botev
    TI__Expert 8210 points

    Hi,

    Thank you! So we have to enable CPUFreq firstly? I am wondering what's the default cpufreq if not enable?

  • 0 in reply to Nancy Wang
    TI__Guru**** 170625 points

    Nancy Wang said:
    So we have to enable CPUFreq firstly?

    If you need to use DVFS dynamic power management technique in userspace, then you have to enable cpufreq in kernel.

    Nancy Wang said:
    I am wondering what's the default cpufreq if not enable?

    The Cortex-A8 CPU frequency is setup in u-boot code base. It is set to the MAX frequency it can support. Refer to the below u-boot files:

    u-boot-2019.01/arch/arm/mach-omap2/am33xx/clock.c  : setup_dplls() ->  do_setup_dpll(&dpll_mpu_regs, params);

    u-boot-2019.01/board/ti/am335x/board.c : get_dpll_mpu_params()

    Regards,
    Pavel

  • 0 in reply to Pavel Botev
    TI__Expert 8210 points

    Hi,

    The customer had built CPUFreq referring to the link above.

    But when he executed  cat/sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq, there is no result.

    Is it related to his hardware?

     

     

  • 0 in reply to Nancy Wang
    TI__Guru**** 170625 points

    Nancy,

    From what I understand, you are using AM335x custom board. You need to check two things:

    1. Check your DTS file. Refer again to the user guide, section "DT Configuration"

    2. You need to have PMIC that support DVFS

    Can you also attach your .config file?

    Check also below e2e thread:

    Regards,
    Pavel