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Hi Alan, I have few more questions about run time power management: 1) Please correct me if i am wrong. If there is a bus driver that is managing various power domains, and suppose this domain has some child devices. Then child has to inform run time Power management core i am idle and i want to go to get suspended, then run time pm core will notify the bus driver of child and then bus driver calls the corresponding child's suspend. right? 2) run time power management can be done at device "type" and "class". But what does mean of this device type. what use cases are defined for run time power management for device "type"? Regards Raj > Date: Thu, 1 Jul 2010 10:03:46 -0400 > From: stern@xxxxxxxxxxxxxxxxxxx > To: rajkumar278@xxxxxxxxxxx > CC: linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx > Subject: RE: [linux-pm] About run time power management in linux > > On Thu, 1 Jul 2010, Raj Kumar wrote: > > > Hi Alan, > > > > > > > > I have seen in run time power management helper functions. I have some questions during deep sleep modes > > > > and runtime sleep modes. > > > > > > > > 1) I have seen the code and found that when System wants to go to suspend (deep sleep mode), it has to check for > > > > pm_runtime_barrier which inturn sees if there is a pending runtime resume then it will not allow system to supend. > > > > So it means system suspend can not be done forcefully if the some peripheral jobs are running, correct? > > Yes. The system suspend will have to wait until the runtime PM > activity is finished. > > > 2) it means when System deep sleep is going on, run time suspend will never come to peripheral as it checks for usage counter and > > > > if it is zero then it will ask try again. > > Basically yes, although you have the reason backward. If the usage > count is _non-zero_ then runtime suspend won't occur. > > > 3) if run time suspend is going on, Then if system wants to go into deep sleep mode, it will wait for run time suspend to finish and then > > > > gracefully do the shutdown. correct? > > Yes. > > > 4) Is it mandatory for peripheral driver but not the bus driver to implement runtime_idle operation? > > None of these are mandatory; it all depends on the bus subsystem. > Some subsystems don't implement runtime PM at all. > > Alan Stern > |
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