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AM5728: Platform power management

solid repellent
Intellectual 850 points
Part Number: AM5728

Hello,

I ran some CPU bound benchmarks and found that the CPU power consumption is almost negligible when compared to the platform power consumption (even when no peripherals are attached). The CPU power consumption is few 10's of milli watts. Whereas, the platform power consumption is in between (5 to 7 watts). Can anybody comment on this? Especially it looks like platform power is less bound to CPU computation, as it continues to draw the baseline power even after program termination. Is it platform dependent? If yes how?

Also, is there a way to completely power off the USB's, HDMI and other devices on the platform? I have read that at least for the USB's, at the most they can go into suspend mode and it is not possible to completely power them off. I am not exactly sure though. 

Thank you for your time.

  • 0
    TI__Guru**** 393215 points
    The PM experts have been notified. They will respond here.
  • 0
    TI__Genius 13567 points
    Hello,
    I assume you are using the AM5728 GP EVM, could you tell me how are you making these power measurements? And what OS are you running?

    Regards,
    Ahmad
  • 0 in reply to Ahmad_Rashed
    Intellectual 850 points
    Hello,

    I am using linux on TI AM572x EVM (www.ti.com/.../TMDSEVM572X). I am using compact data acquisition device from national instruments (NI cDAQ - 9174) with two modules, NI 9227 to measure current and NI 9215 to measure voltage. We use them to measure both the platform power (DC power) and the CPU power (by measuring the voltage drop across the shunt resistor provided on the board).

    On the CPU we run some benchmarks. For the time being one core is idle and the benchmark is run on the other core and we measure its power consumption. Let me know if you need fine grain information on our settings.
  • 0 in reply to solid repellent
    TI__Genius 13567 points

    I'm curious to find out why you see a "few 10's of milli watts" on the CPU side. The ARM core might not be going to idle mode so when you apply a load the power difference is negligible. In the Matrix GUI, find the "Power" menu, then change the governor to "ondemand" instead of "userspace". Let's see if that lowers your platform consumption during idle.

    A few notes:

    The DDR modules on the board are fairly large consumers of power but unfortunately that rail is not available to measure or monitor. The VDD_DDR rail is supplied by an LDO on the VDD_3V3 rail. In your own custom board design you can use fewer total memory modules to reduce power consumption. If you only use 1 memory module you can eliminate the VTT termination supply entirely which we find to be very power hungry too. This DDR topology is called point-to-point.

    The GPU is going to be another large consumer of power. If you are not using a display/graphics acceleration you can disable the GPU. Two steps are needed to do this: 1st) disable the GPU in Linux / device tree. 2nd) disable the power domain to the GPU through the PRCM (see TRM chapter 3.10.10).