[PATCH v8 1/3] PCI: Add helper to check if any of ancestor device support D3cold

[Kai-Heng Feng]

In addition to nearest upstream bridge, driver may want to know if the
entire hierarchy can be powered off to perform different action.

So walk higher up the hierarchy to find out if any device has valid
_PR3.

The user will be introduced in next patch.

Signed-off-by: Kai-Heng Feng <kai.heng.feng at canonical.com>
---
v8:
 - No change.

 drivers/pci/pci.c   | 16 ++++++++++++++++
 include/linux/pci.h |  2 ++
 2 files changed, 18 insertions(+)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index e5f243dd4288..7a5662f116b8 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -6225,6 +6225,22 @@ bool pci_pr3_present(struct pci_dev *pdev)
 		acpi_has_method(adev->handle, "_PR3");
 }
 EXPORT_SYMBOL_GPL(pci_pr3_present);
+
+bool pci_ancestor_pr3_present(struct pci_dev *pdev)
+{
+	struct pci_dev *parent = pdev;
+
+	if (acpi_disabled)
+		return false;
+
+	while ((parent = pci_upstream_bridge(parent))) {
+		if (pci_pr3_present(pdev))
+			return true;
+	}
+
+	return false;
+}
+EXPORT_SYMBOL_GPL(pci_ancestor_pr3_present);
 #endif
 
 /**
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 16493426a04f..cd71ebfd0f89 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -2620,10 +2620,12 @@ struct irq_domain *pci_host_bridge_acpi_msi_domain(struct pci_bus *bus);
 void
 pci_msi_register_fwnode_provider(struct fwnode_handle *(*fn)(struct device *));
 bool pci_pr3_present(struct pci_dev *pdev);
+bool pci_ancestor_pr3_present(struct pci_dev *pdev);
 #else
 static inline struct irq_domain *
 pci_host_bridge_acpi_msi_domain(struct pci_bus *bus) { return NULL; }
 static inline bool pci_pr3_present(struct pci_dev *pdev) { return false; }
+static inline bool pci_ancestor_pr3_present(struct pci_dev *pdev) { return false; }
 #endif
 
 #ifdef CONFIG_EEH
-- 
2.34.1