path: root/drivers/usb/core/hub.c
diff options
authorSarah Sharp <sarah.a.sharp@linux.intel.com>2011-06-05 23:22:22 -0700
committerSarah Sharp <sarah.a.sharp@linux.intel.com>2011-06-15 14:05:18 -0700
commitfccf4e86200b8f5edd9a65da26f150e32ba79808 (patch)
tree6de67060ac3825e46f67682a69298bddc8825535 /drivers/usb/core/hub.c
parentfa75ac379e63c2864e9049b5e8615e40f65c1e70 (diff)
USB: Free bandwidth when usb_disable_device is called.
Tanya ran into an issue when trying to switch a UAS device from the BOT configuration to the UAS configuration via the bConfigurationValue sysfs file. Before installing the UAS configuration, set_bConfigurationValue() calls usb_disable_device(). That function is supposed to remove all host controller resources associated with that device, but it leaves some state in the xHCI host controller. Commit 0791971ba8fbc44e4f476079f856335ed45e6324 usb: allow drivers to use allocated bandwidth until unbound added a call to usb_disable_device() in usb_set_configuration(), before the xHCI bandwidth functions were invoked. That commit fixed a bug, but also introduced a bug that is triggered when a configured device is switched to a new configuration. usb_disable_device() goes through all the motions of unbinding the drivers attached to active interfaces and removing the USB core structures associated with those interfaces, but it doesn't actually remove the endpoints from the internal xHCI host controller bandwidth structures. When usb_disable_device() calls usb_disable_endpoint() with reset_hardware set to true, the entries in udev->ep_out and udev->ep_in will be set to NULL. Usually, when the USB core installs a new configuration, usb_hcd_alloc_bandwidth() will drop all non-NULL endpoints in udev->ep_out and udev->ep_in before adding any new endpoints. However, when the new UAS configuration was added, all those entries were null, so none of the old endpoints in the BOT configuration were dropped. The xHCI driver blindly added the UAS configuration endpoints, and some of the endpoint addresses overlapped with the old BOT configuration endpoints. This caused the xHCI host to reject the Configure Endpoint command. Now that the xHCI driver code is cleaned up to reject a double-add of active endpoints, we need to fix the USB core to properly drop old endpoints in usb_disable_device(). If the host controller driver needs bandwidth checking support, make usb_disable_device() call usb_disable_endpoint() with reset_hardware set to false, drop the endpoints from the xHCI host controller, and then call usb_disable_endpoint() again with reset_hardware set to true. The first call to usb_disable_endpoint() will cancel any pending URBs and wait on them to be freed in usb_hcd_disable_endpoint(), but will keep the pointers in udev->ep_out and udev->ep in intact. Then usb_hcd_alloc_bandwidth() will use those pointers to know which endpoints to drop. The final call to usb_disable_endpoint() will do two things: 1. It will call usb_hcd_disable_endpoint() again, which should be harmless since the ep->urb_list should be empty after the first call to usb_disable_endpoint() returns. 2. It will set the entries in udev->ep_out and udev->ep in to NULL, and call usb_hcd_disable_endpoint(). That call will have no effect, since the xHCI driver doesn't set the endpoint_disable function pointer. Note that usb_disable_device() will now need to be called with hcd->bandwidth_mutex held. This should be backported to kernels as old as 2.6.32. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Reported-by: Tanya Brokhman <tlinder@codeaurora.org> Cc: ablay@codeaurora.org Cc: Alan Stern <stern@rowland.harvard.edu> Cc: stable@kernel.org
Diffstat (limited to 'drivers/usb/core/hub.c')
1 files changed, 3 insertions, 0 deletions
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 90ae1753dda..ca339bc799e 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -1634,6 +1634,7 @@ void usb_disconnect(struct usb_device **pdev)
struct usb_device *udev = *pdev;
int i;
+ struct usb_hcd *hcd = bus_to_hcd(udev->bus);
if (!udev) {
pr_debug ("%s nodev\n", __func__);
@@ -1661,7 +1662,9 @@ void usb_disconnect(struct usb_device **pdev)
* so that the hardware is now fully quiesced.
dev_dbg (&udev->dev, "unregistering device\n");
+ mutex_lock(hcd->bandwidth_mutex);
usb_disable_device(udev, 0);
+ mutex_unlock(hcd->bandwidth_mutex);