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AM335x PM engine

Guillaume Guillaume
Prodigy 70 points

Hello,

I would like to know if the linux PSP for AM335x is based on ACPI or APM (problably  an other standard) for power management. CpuFreq or CpuIdle are based on a standard ?

On Power management User Guide, I saw some functions to control the power management (like am33xx_pm_suspend() or am33xx_enter_idle()) but where I can found a documentation about this API ?

Thank you,

Regards,

Guillaume

  • 0
    TI__Intellectual 1585 points

    To the best of my knowledge, power management for AM335x is not based on a particular standard such as ACPI or APM.

    Cpufreq and cpuidle are linux kernel subsystems.  I've not seen anything to indicate that these are standards based implementations.

    Regarding am33xx_pm_suspend() and am33xx_enter_idle(), you won't find documentation on these specifically.  am33xx_pm_suspend() is part of AM335x platform specific code, which is called from kernel through callbacks in the platform_suspend_ops structure.  You wouldn't call this function as an API.

    Similarly, you wouldn't want to directly call am33xx_enter_idle().  It is used to put the AM335x into idle states when Linux detects that the CPU has no useful work to do.  This is managed automatically by the cpuidle subsystem.  am33xx_enter_idle() is simply the platform specific callback that does the SoC-specific work (namely, putting the MPU into WFI mode).

  • 0 in reply to Greg Guyotte
    Prodigy 70 points

    Thank you for your answer.

    We need a very agressive power saving policy from the AM335x.

    OPPx is a little confuse for me. It is possible to have a MPU frequency lower than 275Mhz  with cpufreq ? (I guess that the driver must be modified ...)

    Regards,

    Guillaume