On Fri, 25 Nov 2016, Sakari Ailus wrote:
> Hi Alan and others,
>
> On Thu, Nov 24, 2016 at 09:15:39PM -0500, Alan Stern wrote:
> > On Fri, 25 Nov 2016, Laurent Pinchart wrote:
> >
> > > Dear linux-pm developers, what's the suggested way to ensure that a
> > > runtime-
> > > pm-enabled driver can run fine on a system with CONFIG_PM disabled ?
> >
> > The exact point of your question isn't entirely clear. In the most
> > literal sense, the best ways to ensure this are (1) audit the code, and
> > (2) actually try it.
> >
> > I have a feeling this doesn't quite answer your question, however. :-)
>
> The question is related to devices that require certain power-up and
> power-down sequences that are now implemented as PM runtime hooks that,
> without CONFIG_PM defined, will not be executed. Is there a better way than
> to handle this than have an implementation in the driver for the PM runtime
> and non-PM runtime case separately?
Yes, there is a better way. For the initial power-up and final
power-down sequences, don't rely on the PM core to invoke the
callbacks. Just call them directly, yourself.
For example, as part of the probe routine, instead of doing this:
pm_runtime_set_suspended(dev);
pm_runtime_enable(dev);
pm_runtime_get_sync(dev);
Do this:
pm_runtime_set_active(dev);
pm_runtime_get_noresume(dev);
pm_runtime_enable(dev);
/*
* In case CONFIG_PM is disabled, invoke the runtime-resume
* callback directly.
*/
my_runtime_resume(dev);
Alan Stern
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