[PATCH 4.13 002/160] usb: dwc3: ep0: fix DMA starvation by assigning req->trb on ep0

[Greg Kroah-Hartman]

4.13-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Felipe Balbi <felipe.balbi@xxxxxxxxxxxxxxx>

commit 55168470835688e5da5828cdcf1b1498d7baadb1 upstream.

If we don't assign a TRB to ep0 requests, we won't be able to unmap
the request later on resulting in starvation of DMA resources.

Fixes: 4a71fcb8ac5f ("usb: dwc3: gadget: only unmap requests from DMA if mapped")
Reported-by: Thinh Nguyen <Thinh.Nguyen@xxxxxxxxxxxx>
Tested-by: Thinh Nguyen <Thinh.Nguyen@xxxxxxxxxxxx>
Signed-off-by: Felipe Balbi <felipe.balbi@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/usb/dwc3/ep0.c |    7 +++++++
 1 file changed, 7 insertions(+)

--- a/drivers/usb/dwc3/ep0.c
+++ b/drivers/usb/dwc3/ep0.c
@@ -990,6 +990,8 @@ static void __dwc3_ep0_do_control_data(s
 					 DWC3_TRBCTL_CONTROL_DATA,
 					 true);
 
+		req->trb = &dwc->ep0_trb[dep->trb_enqueue - 1];
+
 		/* Now prepare one extra TRB to align transfer size */
 		dwc3_ep0_prepare_one_trb(dep, dwc->bounce_addr,
 					 maxpacket - rem,
@@ -1015,6 +1017,8 @@ static void __dwc3_ep0_do_control_data(s
 					 DWC3_TRBCTL_CONTROL_DATA,
 					 true);
 
+		req->trb = &dwc->ep0_trb[dep->trb_enqueue - 1];
+
 		/* Now prepare one extra TRB to align transfer size */
 		dwc3_ep0_prepare_one_trb(dep, dwc->bounce_addr,
 					 0, DWC3_TRBCTL_CONTROL_DATA,
@@ -1029,6 +1033,9 @@ static void __dwc3_ep0_do_control_data(s
 		dwc3_ep0_prepare_one_trb(dep, req->request.dma,
 				req->request.length, DWC3_TRBCTL_CONTROL_DATA,
 				false);
+
+		req->trb = &dwc->ep0_trb[dep->trb_enqueue];
+
 		ret = dwc3_ep0_start_trans(dep);
 	}