usb: gadget: function: u_ether: don't starve tx request queue

commit 6c83f77278f17a7679001027e9231291c20f0d8a upstream.

If we don't guarantee that we will always get an
interrupt at least when we're queueing our very last
request, we could fall into situation where we queue
every request with 'no_interrupt' set. This will
cause the link to get stuck.

The behavior above has been triggered with g_ether
and dwc3.

Reported-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Willy Tarreau <w@1wt.eu>

diff --git a/drivers/usb/gadget/u_ether.c b/drivers/usb/gadget/u_ether.c
index 80294f320e16b297fa79a9a878953ce526c09ce2..c93e6a1bbc4b9ca721424c5fc236341ba008a1da 100644 (file)
--- a/drivers/usb/gadget/u_ether.c
+++ b/drivers/usb/gadget/u_ether.c
@@ -958,9 +958,11 @@ static netdev_tx_t eth_start_xmit(struct sk_buff *skb,
 
        req->length = length;
 
-       /* throttle highspeed IRQ rate back slightly */
+       /* throttle high/super speed IRQ rate back slightly */
        if (gadget_is_dualspeed(dev->gadget) &&
-                        (dev->gadget->speed == USB_SPEED_HIGH)) {
+                        (dev->gadget->speed == USB_SPEED_HIGH ||
+                     dev->gadget->speed == USB_SPEED_SUPER) &&
+                                       !list_empty(&dev->tx_reqs)) {
                dev->tx_qlen++;
                if (dev->tx_qlen == (qmult/2)) {
                        req->no_interrupt = 0;