linux-kernel - Re: Runtime power management during system resume

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Date:	Tue, 24 Aug 2010 10:30:25 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Raj Kumar <rajkumar278@...mail.com>
cc:	linux-kernel@...r.kernel.org
Subject: Re: Runtime power management during system resume

On Tue, 24 Aug 2010, Raj Kumar wrote:

> Hi Alan,
>  
> I have implemented the run time power management in my drivers. I have one
> issue regarding System resume.
>  
> When the system sleep is triggered as it is mentioned that Power management
> core will increment the power_usage counter during prepare and decrements when complete
> is called.
>  
> Now I have few questions:
>  
> 1) When the system resume is done, it does not increase the power_usage counter.
>  right?

That's right.

> So Does then the driver need to update the power_usage counter with run time power management
> core and again set it to active means RPM_ACTIVE?

Read section 6 of Documentation/power/runtime_pm.h.  It explains this.

> 2) Suppose device is active, means its power_usage counter is already one, Now during system
> sleep, does the driver first suspend it with run time power management core and then continue
> System suspend?

No.

> 3) Because I have seen the code of power management core and I did not see the that during
> system suspend, run time power management status is updated means RPM_SUSPENDED.
> right?

I don't understand your question.

Alan Stern

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