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system idle vs device idle

ranchu
Guru 20755 points

Hello,

When the system is idle mode (using cpuidle) , does it mean that all devices are also get into idle in terms of PM (power-management) or is it that each device is responsible for its own idle/sleep mode ?
If each device is responsible for its own, than is the meaning of idle system (cpuidle) ?

What is the different between idle/sleep/resume mode ?

Thanks,
Ran

  • 0
    TI__Guru** 116100 points

    Hi Ran,

    CPUIdle PM framework would run into power down mode when CPU don't have thread/work to process.

    CPUIdle / CPUFreq -> PM frameworks (automated)

    It has some governors to control, like userspace, performance,conservative etc.,

    suspend/resume -> These functions are used in platform drivers and these function will be called when we initiate PM manually like "echo "mem" /sys/power/state"

    These are the generic to linux.

    If you want PM to be device specific then you should check your appropriate TRM guide ie Power Management.

    Ex:

    USB PHY shutdown

    Ethernet PHY shutdown

    Module clock OFF

    PLL bypass

    DDR self refresh mode

    DEEPSLEEP mode

    etc.,