ACPI / PM: Fix potential problem in acpi_device_get_power()

Theoretically, in some situations acpi_device_get_power() may return
an incorrect result, because the settings of the power resources
depended on by the device may indicate a power state shallower than
the actual power state of the device.

Say that two devices, A and B, depend on two power resources, X and
Y, in such a way that _PR0 for both A and B list both X and Y and
_PR3 for both A and B list power resource Y alone.  Also suppose
that _PS0 and _PS3 are present for both A and B.  Then, if devices
A and B are initially in D0, power resources X and Y are initially
"on" and their reference counters are equal to 2.  To put device A
into power state D3hot the kernel will decrement the reference
counter of power resource X, but that power resource won't be turned
off, because it is still in use by device B (its reference counter is
equal to 1).  Next, _PS3 will be executed for device A.  Afterward
the configuration of the power resources will indicate that device
A is in power state D0 (both X and Y are "on"), but in fact it is
in D3hot (because _PS3 has been executed for it).

In that situation, if acpi_device_get_power() is called to get the
power state of device A, it will first execute _PSC for it which
should return 3.  That will cause acpi_device_get_power() to run
acpi_power_get_inferred_state() for device A and the resultant power
state will be D0, which is incorrect.

To fix that change acpi_device_get_power() to first execute
acpi_power_get_inferred_state() for the given device (if it
depends on power resources) and to evaluate _PSC for it subsequently,
so that the result inferred from the power resources configuration
can be amended by the _PSC return value.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Aaron Lu <aaron.lu@intel.com>
Merge branch 'acpi-hotplug-next' into bleeding-edge

* acpi-hotplug-next:
  ACPI / memhotplug: Remove info->failed bit
  ACPI / memhotplug: set info->enabled for memory present at boot time
  ACPI: Verify device status after eject
  acpi: remove reference to ACPI_HOTPLUG_IO
  ACPI: Update _OST handling for notify
  ACPI: Update PNPID match handling for notify
  ACPI: Update PNPID set/free interfaces
  ACPI: Remove acpi_device dependency in acpi_device_set_id()
Merge branch 'acpi-lpss-next' into bleeding-edge

* acpi-lpss-next:
  ACPI / LPSS: make code less confusing for reader
Merge branch 'acpi-pm-next' into bleeding-edge

* acpi-pm-next:
  ACPI / PM: Fix potential problem in acpi_device_get_power()
Merge branch 'acpi-assorted-next' into bleeding-edge

* acpi-assorted-next:
  ACPI / video: Fix applying indexed initial brightness value.
  ACPI / video: Make logic a little easier to understand.
  ACPI / video: Fix brightness control initialization for some laptops.
  ACPI: Use resource_size() in osl.c
  ACPI / acpi_pad: Used PTR_RET
  ACPI: suppress compiler warning in container.c
  ACPI: suppress compiler warning in battery.c
  ACPI: suppress compiler warnings in processor_throttling.c
  ACPI: suppress compiler warnings in button.c
  ACPI: replace kmalloc+memcpy with kmemdup
  ACPI: Remove acpi_pci_bind_root() definition
  ACPI video: ignore BIOS backlight value for HP dm4