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AM57x DVFS Frequency

Michi Yama
Guru 10030 points
Other Parts Discussed in Thread: AM5728

Hi,

I have some questions regarding the frequency value when DVFS using. Please see the below.

1) What is the minimum frequency for each VD_xxx(VD_MPU, VD_DSPEVE, VD_IVA, VD_GPU, VD_CORE and VD_RTC) when DVFS feature using? Is it the frequency that is specified as OPP_NOM? If minimum frequency is not same as OPP_NOM frequency, please let me know the minimum frequency for each power domain(VD_xxx).

2)  What is the minimum voltage for each VD_xxx when DVFS using? Is it the MIN voltage that is specified as MIN voltage of OPP_NOM in AM5728 data manual Table 5-7? If minimum voltage is different from MIN value, please let me know its value.

3)  According to AM5728 TRM - 3.1.2.3 Dynamic Power Switching, it is written in the below.

 When DPS is applied, a processor or system runs at the highest OPP
(maximum frequency and voltage) to complete its tasks quickly, followed by an automatic switch to a low-
power mode for minimum power consumption. DPS is useful when a real-time application is waiting for an
event.

 If the processor will work OPP_NOM setting (not  OPP_OD, OPP_HIGH), how probability is the power consumption reduced? Is this any enough merit to use DPS.   Of course, I know current Linux SDK does not support DPS.

Please advise me.

I appreciate your quick reply.

Best regards,

Michi

       

  • 0
    TI__Guru**** 161600 points
    Hi Michi,

    For questions 1) and 2), YES, your understanding is correct. The minimum frequency for the device voltage domains is OPP_NOM & corresponding voltages are the ones specified in the data manual (see Table 5-7. Voltage Domains Operating Performance Points & Table 5-8. Supported OPP vs Max Frequency).

    Michi Yama said:
    If the processor will work OPP_NOM setting (not OPP_OD, OPP_HIGH), how probability is the power consumption reduced?


    For calculating the power consumption, when device is workin with a specific OPP, you could use the power estimation tool: processors.wiki.ti.com/.../AM572x_Power_Estimation_Tool 

    Michi Yama said:
    Is this any enough merit to use DPS.


    The TRM states: " However, whereas DVFS reduces dynamic and leakage power consumption, DPS reduces only leakage power consumption, at the expense of a slight overhead in dynamic power consumption."

    So if your final goal is reducing the power consumption, I don't think DPS is the better choice, you should use DVFS.



    Best Regards,
    Yordan
  • 0 in reply to Yordan Kovachev
    Guru 10030 points
    Dear Yordan-san,

    Thank you for your quick reply.

    I have one more question.

    If the processor work with OPP_NOM( for example, MPU_CLK=1GHz), I think frequency can't be decreased.
    Does this mean DVFS can't use when OPP_NOM?

    Please advise me again.

    Best regards,
    Michi
  • 0 in reply to Michi Yama
    TI__Guru**** 161600 points
    Hi,

    DVFS aims to reduce the idle time of the system at the cost of power consumption. So when necessary it switches the OPPs to reduce idle time.
    Yes, it seems that DVFS won't be that effective, if you work with the lowest OPP possible. But that doesn't mean you can't have it implemented in your OS.

    Best Regards,
    Yordan