[PATCH 2/5] usb: xhci: correct num_active_eps accounting on allocation failure

[Niklas Neronin <niklas.neronin@linux.intel.com>]

Some host controllers have a global endpoint limit across all slots,
tracked by 'xhci->num_active_eps' when XHCI_EP_LIMIT_QUIRK is set.

During device allocation, EP0 resources are reserved before
xhci_alloc_virt_device() is called, and 'num_active_eps' is incremented
accordingly. If xhci_alloc_virt_device() subsequently fails, the slot is
disabled but the reserved endpoint resource is not released, leaving
'num_active_eps' permanently increased.

Decreasing 'num_active_eps' happens in xhci_handle_cmd_disable_slot(),
which is called upon a Disable Slot completion command.

This causes the driver to gradually lose available endpoint resources
after allocation failures and may eventually prevent new endpoints from
being allocated.

Fix this by decrementing 'num_active_eps' when virtual device allocation
fails.

Signed-off-by: Niklas Neronin <niklas.neronin@linux.intel.com>
---
 drivers/usb/host/xhci.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 4708fabba84a..ca56e0b69415 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -4279,6 +4279,11 @@ int xhci_alloc_dev(struct usb_hcd *hcd, struct usb_device *udev)
 	 */
 	if (!xhci_alloc_virt_device(xhci, slot_id, udev, GFP_NOIO)) {
 		xhci_warn(xhci, "Could not allocate xHCI USB device data structures\n");
+		if (xhci->quirks & XHCI_EP_LIMIT_QUIRK) {
+			spin_lock_irqsave(&xhci->lock, flags);
+			xhci->num_active_eps -= 1;
+			spin_unlock_irqrestore(&xhci->lock, flags);
+		}
 		goto disable_slot;
 	}
 	vdev = xhci->devs[slot_id];
-- 
2.50.1