Re: [linux-pm] calling runtime PM from system PM methods

[Kevin Hilman <khilman@ti.com>]

"Rafael J. Wysocki" <rjw@sisk.pl> writes:

> On Wednesday, June 15, 2011, Kevin Hilman wrote:

[...]

>>
>> From a device driver perspective, system PM is just runtime
>> PM where the "idleness" was forced and only a subset of possible wakeup
>> sources are enabled.
>
> Oh well, I wonder how much of a difference would make you think those things
> are really different. ;-)

Seeing a description of the differences would help.  So far the list is
rather short: wakeups and forcibly quieting the hardware.

I guess I still don't see why system PM cannot be viewed as a special
case of runtime PM, so how about a specific question: From a device
driver perspective, how is system PM anything other than
manually/forcibly creating the right conditions for a runtime PM
transition to happen?

[...]

>> The development effort is primarily
>> focused on implementing efficient runtime PM for an _active_ system.
>> When this is working, implementing system PM is easy: all that is needed
>> is to enable/disable relevant wakeups and force the device to idle.
>> This allows runtime PM to trigger, and the device is suspended.
>
> No, it doesn't.  What you're trying to do is to "maunally" trigger runtime PM

No.  

What I'm trying to do in .suspend() is create the conditions necessary
such that a runtime PM transition will occur *by itself*.  If the right
conditions exist (namely, idle HW, no pending activity, etc.) a runtime
PM transition will happen *on its own*, and will not need to be manually
triggered.  IOW, a runtime PM transition is a side effect of creating
the right idle conditions.

> when _you_ think is suitable.

No, only when a system suspend is requested by the user.

Kevin