linux-imx

PCI / ACPI / PM: Resume all bridges on suspend-to-RAM

Commit 26112ddc254c (PCI / ACPI / PM: Resume bridges w/o drivers on
suspend-to-RAM) attempted to fix a functional regression resulting
from commit c62ec4610c40 (PM / core: Fix direct_complete handling
for devices with no callbacks) by resuming PCI bridges without
drivers (that is, "parallel PCI" ones) during system-wide suspend if
the target system state is not ACPI S0 (working state).

That turns out insufficient, however, as it is reported that, at
least in one case, the platform firmware gets confused if a PCIe
root port is suspended before entering the ACPI S3 sleep state.
That issue was exposed by commit 77b3729ca03 (PCI / PM: Use
SMART_SUSPEND and LEAVE_SUSPENDED flags for PCIe ports) that allowed
PCIe ports to stay in runtime suspend during system-wide suspend
(which is OK for suspend-to-idle, but turns out to be problematic
otherwise).

For this reason, drop the driver check from acpi_pci_need_resume()
and resume all bridges (including PCIe ports with drivers) during
system-wide suspend if the target system state is not ACPI S0.

[If the target system state is ACPI S0, it means suspend-to-idle
 and the platform firmware is not going to be invoked to actually
 suspend the system, so there is no need to resume the bridges in
 that case.]

Fixes: 77b3729ca03 (PCI / PM: Use SMART_SUSPEND and LEAVE_SUSPENDED flags for PCIe ports)
Link: https://bugzilla.kernel.org/show_bug.cgi?id=200675
Reported-by: teika kazura <teika@gmx.com>
Tested-by: teika kazura <teika@gmx.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: 4.16+ <stable@vger.kernel.org> # 4.16+: 26112ddc254c (PCI / ACPI / PM: Resume bridges ...)
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>