PCI / ACPI: Whitelist D3 for more PCIe hotplug ports

In order to have better power management for Thunderbolt PCIe chains,
Windows enables power management for native PCIe hotplug ports if there is
the following ACPI _DSD attached to the root port:

  Name (_DSD, Package () {
      ToUUID ("6211e2c0-58a3-4af3-90e1-927a4e0c55a4"),
      Package () {
          Package () {"HotPlugSupportInD3", 1}
      }
  })

This is also documented in:

  https://docs.microsoft.com/en-us/windows-hardware/drivers/pci/dsd-for-pcie-root-ports#identifying-pcie-root-ports-supporting-hot-plug-in-d3

Do the same in Linux by introducing new firmware PM callback
(->bridge_d3()) and then implement it for ACPI based systems so that the
above property is checked.

There is one catch, though. The initial pci_dev->bridge_d3 is set before
the root port has ACPI companion bound (the device is not added to the PCI
bus either) so we need to look up the ACPI companion manually in that case
in acpi_pci_bridge_d3().

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index eb3125decffe..672ba4d1659e 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -40,6 +40,8 @@ int pci_bus_error_reset(struct pci_dev *dev);
 /**
  * struct pci_platform_pm_ops - Firmware PM callbacks
  *
+ * @bridge_d3: Does the bridge allow entering into D3
+ *
  * @is_manageable: returns 'true' if given device is power manageable by the
  *		   platform firmware
  *
@@ -61,6 +63,7 @@ int pci_bus_error_reset(struct pci_dev *dev);
  * these callbacks are mandatory.
  */
 struct pci_platform_pm_ops {
+	bool (*bridge_d3)(struct pci_dev *dev);
 	bool (*is_manageable)(struct pci_dev *dev);
 	int (*set_state)(struct pci_dev *dev, pci_power_t state);
 	pci_power_t (*get_state)(struct pci_dev *dev);