PCI / PM: Avoid resuming PCI devices during system suspend

Commit f25c0ae2b4c4 (ACPI / PM: Avoid resuming devices in ACPI PM
domain during system suspend) modified the ACPI PM domain's system
suspend callbacks to allow devices attached to it to be left in the
runtime-suspended state during system suspend so as to optimize
the suspend process.

This was based on the general mechanism introduced by commit
aae4518b3124 (PM / sleep: Mechanism to avoid resuming runtime-suspended
devices unnecessarily).

Extend that approach to PCI devices by modifying the PCI bus type's
->prepare callback to return 1 for devices that are runtime-suspended
when it is being executed and that are in a suitable power state and
need not be resumed going forward.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>

1 files changed, 6 insertions, 5 deletions

diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index 887e6bd95af7..741023e94008 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -653,7 +653,6 @@ static bool pci_has_legacy_pm_support(struct pci_dev *pci_dev)
 static int pci_pm_prepare(struct device *dev)
 {
         struct device_driver *drv = dev->driver;
-        int error = 0;
 
         /*
          * Devices having power.ignore_children set may still be necessary for
@@ -662,10 +661,12 @@ static int pci_pm_prepare(struct device *dev)
         if (dev->power.ignore_children)
                 pm_runtime_resume(dev);
 
-        if (drv && drv->pm && drv->pm->prepare)
-                error = drv->pm->prepare(dev);
-
-        return error;
+        if (drv && drv->pm && drv->pm->prepare) {
+                int error = drv->pm->prepare(dev);
+                if (error)
+                        return error;
+        }
+        return pci_dev_keep_suspended(to_pci_dev(dev));
 }