[PATCH] USB: Fix xhci ERDP update issue

["WeitaoWang-oc@zhaoxin.com" <WeitaoWang-oc@zhaoxin.com>]

On some situations, software handles TRB events slower than adding TRBs.
If the number of TRB events to be processed in a given interrupt is 256.
The local variable "event_ring_deq" that records in interrupt handler
is equal to software_dequeue. It will cause driver not update ERDP,then
software dequeue pointer is out of sync with ERDP on interrupt exit.
On the next interrupt, the event ring may full but driver will not
update ERDP as software_dequeue is equal to ERDP.

[  536.377115] xhci_hcd 0000:00:12.0: ERROR unknown event type 37
[  566.933173] sd 8:0:0:0: [sdb] tag#27 uas_eh_abort_handler 0 uas-tag 7 
inflight: CMD OUT
[  566.933181] sd 8:0:0:0: [sdb] tag#27 CDB: Write(10) 2a 00 17 71 e6 78 
00 00 08 00
[  572.041186] xhci_hcd On some situataions,the0000:00:12.0: xHCI host 
not responding to stop endpoint command.
[  572.057193] xhci_hcd 0000:00:12.0: Host halt failed, -110
[  572.057196] xhci_hcd 0000:00:12.0: xHCI host controller not 
responding, assume dead
[  572.057236] sd 8:0:0:0: [sdb] tag#26 uas_eh_abort_handler 0 uas-tag 6 
inflight: CMD
[  572.057240] sd 8:0:0:0: [sdb] tag#26 CDB: Write(10) 2a 00 38 eb cc d8 
00 00 08 00
[  572.057244] sd 8:0:0:0: [sdb] tag#25 uas_eh_abort_handler 0 uas-tag 5 
inflight: CMD

Fixed this issue by update software record local variable when handles 
128 TRB events.

Signed-off-by: Weitao Wang <WeitaoWang-oc@zhaoxin.com>
---
  drivers/usb/host/xhci-ring.c | 1 +
  1 file changed, 1 insertion(+)

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index d0b6806..f970799 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -3141,6 +3141,7 @@ irqreturn_t xhci_irq(struct usb_hcd *hcd)
  		if (event_loop++ < TRBS_PER_SEGMENT / 2)
  			continue;
  		xhci_update_erst_dequeue(xhci, event_ring_deq);
+		event_ring_deq = xhci->event_ring->dequeue;

  		/* ring is half-full, force isoc trbs to interrupt more often */
  		if (xhci->isoc_bei_interval > AVOID_BEI_INTERVAL_MIN)
-- 
2.7.4