Re: Runtime power management during system resume

[Alan Stern <stern@rowland.harvard.edu>]

On Wed, 25 Aug 2010, Raj Kumar wrote:

> But since during system suspend power_usage counter is incremented by 1 But if the device is active
> 
> means its state is RPM_ACTIVE, its power_usage counter is 1 in run time power management core.
> 
>  
> 
> when the system suspend happens, it will also increment the power_usage_counter by 1 during dpm_prepare
> 
>  
> 
> Now   the power_usage_counter is 2.
> 
>  
> 
> So when dpm_complete is invoked, it will decrement the power_usage_counter by 1 during dpm_complete.
> 
>  
> 
> So now when the drivers gets system suspend, its power_usage counter is still 1.
> 
>  
> 
> So what in this scenario, does the device decrements the power_usage counter itself?

Firstly, the _device_ can't change the power_usage counter.  Only the
_driver_ can.  You seem to keep forgetting this point; you need to keep
it straight:

		Driver != Device

Secondly, after the system suspend the power_usage counter has the same
value as it did before.  In your case the usage_counter was 1 before
the system suspend and it is 1 after the system suspend.  Whatever
routine was responsible for setting the counter to 1 originally will
also be responsible for decrementing the counter to 0 some time later.

Alan Stern