[PATCH] PCI/ACPI: Whitelist hotplug ports for D3 if power managed by ACPI

[Lukas Wunner]

Recent laptops with dual AMD GPUs fail to suspend the discrete GPU, thus
causing lockups on system sleep and high power consumption at runtime.
The discrete GPU would normally be suspended to D3cold by turning off
ACPI _PR3 Power Resources of the Root Port above the GPU.

However on affected systems, the Root Port is hotplug-capable and
pci_bridge_d3_possible() only allows hotplug ports to go to D3 if they
belong to a Thunderbolt device or if the Root Port possesses a
"HotPlugSupportInD3" ACPI property.  Neither is the case on affected
laptops.  The reason for whitelisting only specific, known to work
hotplug ports for D3 is that there have been reports of SkyLake Xeon-SP
systems raising Hardware Error NMIs upon suspending their hotplug ports:
https://lore.kernel.org/linux-pci/20170503180426.GA4058@otc-nc-03/

But if a hotplug port is power manageable by ACPI (as can be detected
through presence of Power Resources and corresponding _PS0 and _PS3
methods) then it ought to be safe to suspend it to D3.  To this end,
amend acpi_pci_bridge_d3() to whitelist such ports for D3.

Link: https://gitlab.freedesktop.org/drm/amd/-/issues/1222
Link: https://gitlab.freedesktop.org/drm/amd/-/issues/1252
Link: https://gitlab.freedesktop.org/drm/amd/-/issues/1304
Reported-and-tested-by: Arthur Borsboom <arthurborsboom at gmail.com>
Reported-and-tested-by: matoro <matoro at airmail.cc>
Reported-by: Aaron Zakhrov <aaron.zakhrov at gmail.com>
Reported-by: Michal Rostecki <mrostecki at suse.com>
Reported-by: Shai Coleman <git at shaicoleman.com>
Signed-off-by: Lukas Wunner <lukas at wunner.de>
Cc: stable at vger.kernel.org
Cc: Alex Deucher <alexander.deucher at amd.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki at intel.com>
Cc: Mika Westerberg <mika.westerberg at linux.intel.com>
---
 drivers/pci/pci-acpi.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
index d5869a0..d9aa551 100644
--- a/drivers/pci/pci-acpi.c
+++ b/drivers/pci/pci-acpi.c
@@ -944,6 +944,16 @@ static bool acpi_pci_bridge_d3(struct pci_dev *dev)
 	if (!dev->is_hotplug_bridge)
 		return false;
 
+	/* Assume D3 support if the bridge is power-manageable by ACPI. */
+	adev = ACPI_COMPANION(&dev->dev);
+	if (!adev && !pci_dev_is_added(dev)) {
+		adev = acpi_pci_find_companion(&dev->dev);
+		ACPI_COMPANION_SET(&dev->dev, adev);
+	}
+
+	if (adev && acpi_device_power_manageable(adev))
+		return true;
+
 	/*
 	 * Look for a special _DSD property for the root port and if it
 	 * is set we know the hierarchy behind it supports D3 just fine.
-- 
2.27.0