Re: [PATCH 3/3] PCI / ACPI: Handle sibling devices sharing power resources

[Lukas Wunner <lukas@wunner.de>]

On Thu, Jun 06, 2019 at 04:27:21PM +0200, Rafael J. Wysocki wrote:
> On Thu, Jun 6, 2019 at 4:17 PM Mika Westerberg <mika.westerberg@linux.intel.com> wrote:
> > On Thu, Jun 06, 2019 at 04:08:11PM +0200, Rafael J. Wysocki wrote:
> > > That isn't necessary IMO as long as the device are not accessed.  If
> > > the kernel thinks that a given device is in D3cold and doesn't access
> > > it, then it really doesn't matter too much what state the device is in
> > > physically.  On the first access the device should be reinitialized
> > > anyway.
> >
> > But if the device is configured to wake. For example when it detects a
> > hotplug that state is gone when it goes to D0unitialized.
> 
> For this we'll need a pm_runtime_resume() of the dependent device on
> the resource going "on".
> 
> That means we need a list of devices to resume when the resource goes
> "on" after being taken "off".

An idea would be to model every ACPI power resource as a struct device
and automatically set up a device link from the devices using that
power resource (consumers).  After all dependent devices runtime suspend,
the power resource "device" runtime suspends by turning itself off
(and updating the PCI current_state of dependent devices to D3cold).
When the power resource runtime resumes, it schedules a runtime resume
of all dependent devices.

Thanks,

Lukas