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>

diff --git a/drivers/acpi/property.c b/drivers/acpi/property.c
index 90ba9371bae65d018664a105c767c7a2a40341ea..8c7c4583b52d92c5b323523af8388ce7b14814f4 100644 (file)
--- a/drivers/acpi/property.c
+++ b/drivers/acpi/property.c
@@ -28,6 +28,9 @@ static const guid_t prp_guids[] = {
        /* ACPI _DSD device properties GUID: daffd814-6eba-4d8c-8a91-bc9bbf4aa301 */
        GUID_INIT(0xdaffd814, 0x6eba, 0x4d8c,
                  0x8a, 0x91, 0xbc, 0x9b, 0xbf, 0x4a, 0xa3, 0x01),
+       /* Hotplug in D3 GUID: 6211e2c0-58a3-4af3-90e1-927a4e0c55a4 */
+       GUID_INIT(0x6211e2c0, 0x58a3, 0x4af3,
+                 0x90, 0xe1, 0x92, 0x7a, 0x4e, 0x0c, 0x55, 0xa4),
 };
 
 static const guid_t ads_guid =

diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
index f8436d1c4d45fe6039930cc7dc12f08120812f9b..c8d0549580f442fcbba6778ad8600d68ff3bf551 100644 (file)
--- a/drivers/pci/pci-acpi.c
+++ b/drivers/pci/pci-acpi.c
@@ -519,6 +519,46 @@ static pci_power_t acpi_pci_choose_state(struct pci_dev *pdev)
        return PCI_POWER_ERROR;
 }
 
+static struct acpi_device *acpi_pci_find_companion(struct device *dev);
+
+static bool acpi_pci_bridge_d3(struct pci_dev *dev)
+{
+       const struct fwnode_handle *fwnode;
+       struct acpi_device *adev;
+       struct pci_dev *root;
+       u8 val;
+
+       if (!dev->is_hotplug_bridge)
+               return false;
+
+       /*
+        * 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.
+        */
+       root = pci_find_pcie_root_port(dev);
+       if (!root)
+               return false;
+
+       adev = ACPI_COMPANION(&root->dev);
+       if (root == dev) {
+               /*
+                * It is possible that the ACPI companion is not yet bound
+                * for the root port so look it up manually here.
+                */
+               if (!adev && !pci_dev_is_added(root))
+                       adev = acpi_pci_find_companion(&root->dev);
+       }
+
+       if (!adev)
+               return false;
+
+       fwnode = acpi_fwnode_handle(adev);
+       if (fwnode_property_read_u8(fwnode, "HotPlugSupportInD3", &val))
+               return false;
+
+       return val == 1;
+}
+
 static bool acpi_pci_power_manageable(struct pci_dev *dev)
 {
        struct acpi_device *adev = ACPI_COMPANION(&dev->dev);
@@ -635,6 +675,7 @@ static bool acpi_pci_need_resume(struct pci_dev *dev)
 }
 
 static const struct pci_platform_pm_ops acpi_pci_platform_pm = {
+       .bridge_d3 = acpi_pci_bridge_d3,
        .is_manageable = acpi_pci_power_manageable,
        .set_state = acpi_pci_set_power_state,
        .get_state = acpi_pci_get_power_state,

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 4a1b1f76dc92257aa4ccc448dc1d27f1f10eed4f..e6fcf11f5dccc5467650d96228898648ef9b7946 100644 (file)
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -793,6 +793,11 @@ static inline bool platform_pci_need_resume(struct pci_dev *dev)
        return pci_platform_pm ? pci_platform_pm->need_resume(dev) : false;
 }
 
+static inline bool platform_pci_bridge_d3(struct pci_dev *dev)
+{
+       return pci_platform_pm ? pci_platform_pm->bridge_d3(dev) : false;
+}
+
 /**
  * pci_raw_set_power_state - Use PCI PM registers to set the power state of
  *                           given PCI device
@@ -2518,6 +2523,10 @@ bool pci_bridge_d3_possible(struct pci_dev *bridge)
                if (bridge->is_thunderbolt)
                        return true;
 
+               /* Platform might know better if the bridge supports D3 */
+               if (platform_pci_bridge_d3(bridge))
+                       return true;
+
                /*
                 * Hotplug ports handled natively by the OS were not validated
                 * by vendors for runtime D3 at least until 2018 because there

diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index eb3125decffe14df261817c98138ad3a5b363ff7..672ba4d1659effd3a22900ae32283e15376212be 100644 (file)
--- 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);