[PATCH] PM / Sleep: Fall back to subsystem level PM callbacks for PM domains

[Rafael J. Wysocki]

On Wednesday, May 21, 2014 11:36:20 AM Ulf Hansson wrote:
> On 30 April 2014 14:15, Ulf Hansson <ulf.hansson at linaro.org> wrote:
> > On 30 April 2014 00:52, Rafael J. Wysocki <rjw at rjwysocki.net> wrote:
> >> On Wednesday, April 30, 2014 12:47:28 AM Rafael J. Wysocki wrote:
> >>> On Friday, April 25, 2014 12:44:55 PM Ulf Hansson wrote:
> >>> > Previously once the PM core found a PM domain pointer for a device,
> >>> > but which didn't have a valid PM callback, it falled back to try the
> >>> > driver's PM callback.
> >>> >
> >>> > In this scenario, change the behavior of the PM core to try out the
> >>> > other subsystem level PM callbacks, before it moves on to the driver.
> >>> >
> >>> > This gives provision for PM domains to easier re-use subsystem level
> >>> > code to handle the needed operations.
> >>> >
> >>> > Signed-off-by: Ulf Hansson <ulf.hansson at linaro.org>
> >>>
> >>> Are you sure this is not going to break the existing PM domains?
> >
> > I have checked the current implementations of the PM domains - all are
> > providing the PM callbacks. So this should be safe.
> >
> >>
> >> And even if it isn't, the idea behind PM domains was to provide a mechanism to
> >> bypass the bus types' (etc) PM callbacks, so I'm not liking this patch at all.
> >
> > I understand your view, it's the current mindset we have of the
> > hierarchy of handling the callbacks. I am wondering if it's time to
> > reconsider. :-)
> >
> > To be clear, I don't want to prevent the PM domain from bypassing bus,
> > types etc, that's should be up to each implementation to decide, and
> > this patch won't affect that behaviour.
> >
> > I intend to only simplify for those PM domains that want to re-use the
> > callbacks from bus, types. etc. Currently that's the most of them.
> >
> > a)
> > Those ARM SOCs that implements PM domains, which don't use the generic
> > power domain, cares only about platform devices attached to the
> > platform_bus_type. These are copying the callbacks from the
> > platform_bus_type (using the USE_PLATFORM_PM_SLEEP_OPS macro)  - I
> > assume this is because they need to handle legacy suspend/resume.
> >
> > arch/arm/mach-davinci/pm_domain.c
> > arch/arm/mach-keystone/pm_domain.c
> > arch/arm/mach-omap1/pm_bus.c
> > arch/arm/mach-omap2/omap_device.c
> > drivers/sh/pm_runtime.c
> >
> > b)
> > An actual copy of the bus' PM callbacks to the PM domain's callbacks also exist.
> >
> > drivers/gpu/vga/vga_switcheroo.c:
> > vga_switcheroo_init_domain_pm_ops()
> > vga_switcheroo_init_domain_pm_optimus_hdmi_audio()
> >
> > c)
> > That leaves the generic power domain and acpi power domain, which
> > don't re-use callbacks, but have their own set.
> >
> >
> > The more complicated scenario have not yet been implemented - but I
> > can see it coming. :-)
> > That's when the PM domain wants to re-use callbacks for whatever bus,
> > types etc, the device is attached to.
> >
> > To handle this, the PM domain will have to re-implement the code for
> > walking the hierarchy of callbacks, which is a bit messy. This patch
> > will make it possible for the PM domain to rely on the PM core to
> > handle this instead.
> >
> 
> Hi Rafael,
> 
> Just wanted to understand if you are still considering this patch or
> if think it's the wrong approach?

I said I didn't like the approach IIRC.  I'm not considering it anyway.

Rafael