PCI / PM: Allow runtime PM without callback functions

jhnikula · bjorn-helgaas · commit c5eb1190074c · 2018-12-12T15:37:43.000-06:00
a9c8088 ("i2c: i801: Don't restore config registers on runtime PM") nullified the runtime PM suspend/resume callback pointers while keeping the runtime PM enabled. This caused the SMBus PCI device to stay in D0 with /sys/devices/.../power/runtime_status showing "error" when the runtime PM framework attempted to autosuspend the device. This is due to PCI bus runtime PM, which checks for driver runtime PM callbacks and returns -ENOSYS if they are not set. Since i2c-i801.c doesn't need to do anything device-specific for runtime PM, Jean Delvare proposed this be fixed in the PCI core rather than adding dummy runtime PM callback functions in the PCI drivers. Change pci_pm_runtime_suspend()/pci_pm_runtime_resume() so they allow changing the PCI device power state during runtime PM transitions even if the driver supplies no runtime PM callbacks. This fixes the runtime PM regression on i2c-i801.c. It is not obvious why the code previously required the runtime PM callbacks. The test has been there since the code was introduced by 6cbf821 ("PCI PM: Run-time callbacks for PCI bus type"). On the other hand, a similar change was done to generic runtime PM callbacks in 05aa55d ("PM / Runtime: Lenient generic runtime pm callbacks"). Fixes: a9c8088 ("i2c: i801: Don't restore config registers on runtime PM") Reported-by: Mika Westerberg <mika.westerberg@linux.intel.com> Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Reviewed-by: Jean Delvare <jdelvare@suse.de> Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Cc: stable@vger.kernel.org # v4.18+
diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
@@ -1251,30 +1251,29 @@ static int pci_pm_runtime_suspend(struct device *dev)
 		return 0;
 	}
 
-	if (!pm || !pm->runtime_suspend)
-		return -ENOSYS;
-
 	pci_dev->state_saved = false;
-	error = pm->runtime_suspend(dev);
-	if (error) {
+	if (pm && pm->runtime_suspend) {
+		error = pm->runtime_suspend(dev);
 		/*
 		 * -EBUSY and -EAGAIN is used to request the runtime PM core
 		 * to schedule a new suspend, so log the event only with debug
 		 * log level.
 		 */
-		if (error == -EBUSY || error == -EAGAIN)
+		if (error == -EBUSY || error == -EAGAIN) {
 			dev_dbg(dev, "can't suspend now (%pf returned %d)\n",
 				pm->runtime_suspend, error);
-		else
+			return error;
+		} else if (error) {
 			dev_err(dev, "can't suspend (%pf returned %d)\n",
 				pm->runtime_suspend, error);
-
-		return error;
+			return error;
+		}
 	}
 
 	pci_fixup_device(pci_fixup_suspend, pci_dev);
 
-	if (!pci_dev->state_saved && pci_dev->current_state != PCI_D0
+	if (pm && pm->runtime_suspend
+	    && !pci_dev->state_saved && pci_dev->current_state != PCI_D0
 	    && pci_dev->current_state != PCI_UNKNOWN) {
 		WARN_ONCE(pci_dev->current_state != prev,
 			"PCI PM: State of device not saved by %pF\n",
@@ -1292,7 +1291,7 @@ static int pci_pm_runtime_suspend(struct device *dev)
 
 static int pci_pm_runtime_resume(struct device *dev)
 {
-	int rc;
+	int rc = 0;
 	struct pci_dev *pci_dev = to_pci_dev(dev);
 	const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
 
@@ -1306,14 +1305,12 @@ static int pci_pm_runtime_resume(struct device *dev)
 	if (!pci_dev->driver)
 		return 0;
 
-	if (!pm || !pm->runtime_resume)
-		return -ENOSYS;
-
 	pci_fixup_device(pci_fixup_resume_early, pci_dev);
 	pci_enable_wake(pci_dev, PCI_D0, false);
 	pci_fixup_device(pci_fixup_resume, pci_dev);
 
-	rc = pm->runtime_resume(dev);
+	if (pm && pm->runtime_resume)
+		rc = pm->runtime_resume(dev);
 
 	pci_dev->runtime_d3cold = false;
 
