commit f161ead70fa6a62e432dff6e9dab8e3cfbeabea6
Author: Mathias Nyman <mathias.nyman@linux.intel.com>
Date:   Fri Jan 9 17:18:28 2015 +0200

    xhci: Check if slot is already in default state before moving it there
    
    Solves xhci error cases with debug messages:
    xhci_hcd 0000:00:14.0: Setup ERROR: setup context command for slot 1.
    usb 1-6: hub failed to enable device, error -22
    
    xhci will give a context state error if we try to set a slot in default
    state to the same default state with a special address device command.
    
    Turns out this happends in several cases:
    - retry reading the device rescriptor in hub_port_init()
    - usb_reset_device() is called for a slot in default state
    - in resume path, usb_port_resume() calls hub_port_init()
    
    The default state is usually reached from most states with a reset device
    command without any context state errors, but using the address device
    command with BSA bit set (block set address) only works from the enabled
    state and will otherwise cause context error.
    
    solve this by checking if we are already in the default state before issuing
    a address device BSA=1 command.
    
    Fixes: 48fc7dbd52c0 ("usb: xhci: change enumeration scheme to 'new scheme'")
    Cc: <stable@vger.kernel.org> # v3.14+
    Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 01fcbb5..c50d8d2 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -3803,6 +3803,15 @@ static int xhci_setup_device(struct usb_hcd *hcd, struct usb_device *udev,
 		return -EINVAL;
 	}

+	if (setup == SETUP_CONTEXT_ONLY) {
+		slot_ctx = xhci_get_slot_ctx(xhci, virt_dev->out_ctx);
+		if (GET_SLOT_STATE(le32_to_cpu(slot_ctx->dev_state)) ==
+		    SLOT_STATE_DEFAULT) {
+			xhci_dbg(xhci, "Slot already in default state\n");
+			return 0;
+		}
+	}
+
 	command = xhci_alloc_command(xhci, false, false, GFP_KERNEL);
 	if (!command)
 		return -ENOMEM;