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authorAlan Stern <stern@rowland.harvard.edu>2014-05-23 10:45:54 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-06-11 11:54:13 -0700
commit6bf64643e2a6578d5ef64a8bcbd0f9b993063120 (patch)
tree434ea6322eafbc4a88f9dab111bade5eff74aad8
parentb3fe93951b249262799da15d571ea7240f323f6e (diff)
USB: Avoid runtime suspend loops for HCDs that can't handle suspend/resume
commit 8ef42ddd9a53b73e6fc3934278710c27f80f324f upstream. Not all host controller drivers have bus-suspend and bus-resume methods. When one doesn't, it will cause problems if runtime PM is enabled in the kernel. The PM core will attempt to suspend the controller's root hub, the suspend will fail because there is no bus-suspend routine, and a -EBUSY error code will be returned to the PM core. This will cause the suspend attempt to be repeated shortly thereafter, in a never-ending loop. Part of the problem is that the original error code -ENOENT gets changed to -EBUSY in usb_runtime_suspend(), on the grounds that the PM core will interpret -ENOENT as meaning that the root hub has gotten into a runtime-PM error state. While this change is appropriate for real USB devices, it's not such a good idea for a root hub. In fact, considering the root hub to be in a runtime-PM error state would not be far from the truth. Therefore this patch updates usb_runtime_suspend() so that it adjusts error codes only for non-root-hub devices. Furthermore, the patch attempts to prevent the problem from occurring in the first place by not enabling runtime PM by default for root hubs whose host controller driver doesn't have bus_suspend and bus_resume methods. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Reported-by: Will Deacon <will.deacon@arm.com> Tested-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/usb/core/driver.c9
-rw-r--r--drivers/usb/core/hub.c15
2 files changed, 19 insertions, 5 deletions
diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
index 4ebf1b2034e8..39c7cd6ffa4b 100644
--- a/drivers/usb/core/driver.c
+++ b/drivers/usb/core/driver.c
@@ -1801,10 +1801,13 @@ int usb_runtime_suspend(struct device *dev)
if (status == -EAGAIN || status == -EBUSY)
usb_mark_last_busy(udev);
- /* The PM core reacts badly unless the return code is 0,
- * -EAGAIN, or -EBUSY, so always return -EBUSY on an error.
+ /*
+ * The PM core reacts badly unless the return code is 0,
+ * -EAGAIN, or -EBUSY, so always return -EBUSY on an error
+ * (except for root hubs, because they don't suspend through
+ * an upstream port like other USB devices).
*/
- if (status != 0)
+ if (status != 0 && udev->parent)
return -EBUSY;
return status;
}
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index d498d03afdbd..3baa51bf8a6a 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -1679,8 +1679,19 @@ static int hub_probe(struct usb_interface *intf, const struct usb_device_id *id)
*/
pm_runtime_set_autosuspend_delay(&hdev->dev, 0);
- /* Hubs have proper suspend/resume support. */
- usb_enable_autosuspend(hdev);
+ /*
+ * Hubs have proper suspend/resume support, except for root hubs
+ * where the controller driver doesn't have bus_suspend and
+ * bus_resume methods.
+ */
+ if (hdev->parent) { /* normal device */
+ usb_enable_autosuspend(hdev);
+ } else { /* root hub */
+ const struct hc_driver *drv = bus_to_hcd(hdev->bus)->driver;
+
+ if (drv->bus_suspend && drv->bus_resume)
+ usb_enable_autosuspend(hdev);
+ }
if (hdev->level == MAX_TOPO_LEVEL) {
dev_err(&intf->dev,