Re: REQ_PM vs REQ_TYPE_PM_RESUME

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On Thu, 9 Jan 2014, Phillip Susi wrote:

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> On 1/9/2014 11:14 AM, Alan Stern wrote:
> > That's true, but it isn't a problem.  We know that requests with
> > REQ_PM are sent only at certain, controlled times.  In particular,
> > the only time such a request would be sent while the disk is
> > RPM_SUSPENDED is during a system resume.
> 
> Yes, but if the disk and port were both already RPM_SUSPENDED when the
> system was suspended, and so the port is still RPM_SUSPENDED when the
> disk's system resume method is called, then it can't communicate with
> the disk.

The port should not be runtime suspended during system resume.  It 
should always go to runtime active.
 
> >> We need to put the device into one of the transitioning states
> >> to block other IO, without allowing the port to suspend.
> > 
> > No, we only need to make sure that the port doesn't go into runtime
> >  suspend while we carry out the "is the disk spinning" test.
> 
> Well how else do you do that other than with the transition states?

pm_runtime_get_noresume(dev->parent).

Alan Stern

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