Revert "usb: dwc3: gadget: always decrement by 1"

This reverts commit 6f8245b4e37c ("usb: dwc3: gadget: always decrement
by 1").

We can't always decrement this value.

We should decrement only if the calculation of free slots results in a
LINK TRB being among one of the free slots (dequeue < enqueue).

Otherwise, if the LINK TRB is not among the free slots then it should
not be decremented.

Signed-off-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 7a8d3d822b54..122e64df2f4d 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -884,9 +884,12 @@ static u32 dwc3_calc_trbs_left(struct dwc3_ep *dep)
                 return DWC3_TRB_NUM - 1;
         }
 
-        trbs_left = dep->trb_dequeue - dep->trb_enqueue - 1;
+        trbs_left = dep->trb_dequeue - dep->trb_enqueue;
         trbs_left &= (DWC3_TRB_NUM - 1);
 
+        if (dep->trb_dequeue < dep->trb_enqueue)
+                trbs_left--;
+
         return trbs_left;
 }