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

Rafael J. Wysocki
2019-06-13T17:10:48Z

On Thursday, June 6, 2019 4:36:06 PM CEST Mika Westerberg wrote:
> 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".
>
> OK, thanks.

Basically, at the pci_acpi_setup() time dev and adev need to be passed to a function that
will add dev as a "dependent device" for each of the power resources in the adev's D0
list.

Next whenever a power resource with a list of "dependent devices" goes _ON successfully,
pm_request_resume() needs to be called for each device in that list.

Finally, at the pci_acpi_cleanup() time, dev needs to be removed from the lists of
"dependent devices" for all power resources in its ACPI companion's D0 list.

At least that's how I see that.