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cpuidle - minimum time for idle

ranchu
Guru 20755 points

Hello,

Does anybody knows what's the minimum time for cpuidle ? We will use the menu governer.

from menu governer documentation: "

menu uses a running average for this correction factor, however it uses a

set of factors, not just a single factor. This stems from the realization

that the ratio is dependent on the order of magnitude of the expected

duration; if we expect 500 milliseconds of idle time the likelihood of

getting an interrupt very early is much higher than if we expect 50 micro

seconds of idle time"

Thanks

Ran

  • 0
    TI__Guru 65405 points

    Hi Ran,

    As you read probably in the Linux/drivers/cpuidle/governors/menu.c file comments it is not correct to talk about precise time necessary for going to cpu idle and for changing the state in general due to influence of  various independent factors.

    BR

    Tsvetolin Shulev

  • 0 in reply to Cvetolin Shulev-XID
    Guru 20755 points

    Hi Tsvetolin,

    Is it correct to assume that the retention state time will be at least more than tens of seconds ? What will actually get the system out of cpuidle ? Is it any wakeup source ? Is it SW timer too  (such as udelay command) ?

    Thanks

    Ran

  • 0 in reply to ranchu
    TI__Guru 65405 points

    Ran,

    Time of tens of seconds seems to me very long in general case if there is no some unexpected reason for delay. In general case the time which I observe in various boars is in rage from less then 1 second to a few seconds.

    About system wake-up - there are three types of wake-up events:
    Global: Generated on a particular device event (device wakeup, voltage transition completed, DPLL recalibration, etc.).
    Module: Functional wake-up event issued from a module, which wakes up the domain where the module resides. It can also directly wake up the MPU or the IVA2.2 processor
    Dependency: A power domain can wake up on the wakeup of another power domain.

    For more detail read section 4.8 PRCM Idle and Wake-Up Management in the OMAP35x TRM.

    BR

    Tsvetolin Shulev