PCI/ASPM: Add pcie_aspm_enabled()

Add a function checking whether or not PCIe ASPM has been enabled for
a given device.

It will be used by the NVMe driver to decide how to handle the
device during system suspend.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/pcie/aspm.c

@@ -1170,6 +1170,26 @@ static int pcie_aspm_get_policy(char *buffer, const struct kernel_param *kp)
 module_param_call(policy, pcie_aspm_set_policy, pcie_aspm_get_policy,
 	NULL, 0644);
 
+/**
+ * pcie_aspm_enabled - Check if PCIe ASPM has been enabled for a device.
+ * @pdev: Target device.
+ */
+bool pcie_aspm_enabled(struct pci_dev *pdev)
+{
+	struct pci_dev *bridge = pci_upstream_bridge(pdev);
+	bool ret;
+
+	if (!bridge)
+		return false;
+
+	mutex_lock(&aspm_lock);
+	ret = bridge->link_state ? !!bridge->link_state->aspm_enabled : false;
+	mutex_unlock(&aspm_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(pcie_aspm_enabled);
+
 #ifdef CONFIG_PCIEASPM_DEBUG
 static ssize_t link_state_show(struct device *dev,
 		struct device_attribute *attr,

include/linux/pci.h

@@ -1567,8 +1567,10 @@ extern bool pcie_ports_native;
 
 #ifdef CONFIG_PCIEASPM
 bool pcie_aspm_support_enabled(void);
+bool pcie_aspm_enabled(struct pci_dev *pdev);
 #else
 static inline bool pcie_aspm_support_enabled(void) { return false; }
+static inline bool pcie_aspm_enabled(struct pci_dev *pdev) { return false; }
 #endif
 
 #ifdef CONFIG_PCIEAER