Implement the mechanism for optional explicit status stage for the MUSB
driver. This allows a function driver to specify what to reply for the
status stage. The functionality for an implicit status stage is
retained.

Signed-off-by: Paul Elder <paul.el...@ideasonboard.com>
v1 Reviewed-by: Laurent Pinchart <laurent.pinch...@ideasonboard.com>
v1 Acked-by: Bin Liu <b-...@ti.com>
---
Changes from v2:
- update call to usb_gadget_control_complete to include status
- since sending STALL from the function driver is now done with
  usb_ep_set_halt, there is no need for the internal ep0_send_response to
  take a stall/ack parameter; remove the parameter and make the function
  only send ack, and remove checking for the status reply in the
  usb_request for the status stage

Changes from v1:
- obvious change to implement v2 mechanism laid out by 4/6 of this
  series (send_response, and musb_g_ep0_send_response function has
  been removed, call to usb_gadget_control_complete has been added)
- ep0_send_response's ack argument has been changed from stall
- last_packet flag in ep0_rxstate has been removed, since it is equal to
  req != NULL

 drivers/usb/musb/musb_gadget.c     |  2 ++
 drivers/usb/musb/musb_gadget_ep0.c | 23 +++++++++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/drivers/usb/musb/musb_gadget.c b/drivers/usb/musb/musb_gadget.c
index d3f33f449445..a7a992ab0c9d 100644
--- a/drivers/usb/musb/musb_gadget.c
+++ b/drivers/usb/musb/musb_gadget.c
@@ -145,6 +145,8 @@ __acquires(ep->musb->lock)
 
        trace_musb_req_gb(req);
        usb_gadget_giveback_request(&req->ep->end_point, &req->request);
+       usb_gadget_control_complete(&musb->g, request->explicit_status,
+                       request->status);
        spin_lock(&musb->lock);
        ep->busy = busy;
 }
diff --git a/drivers/usb/musb/musb_gadget_ep0.c 
b/drivers/usb/musb/musb_gadget_ep0.c
index 91a5027b5c1f..bbce8a9d77e4 100644
--- a/drivers/usb/musb/musb_gadget_ep0.c
+++ b/drivers/usb/musb/musb_gadget_ep0.c
@@ -458,6 +458,23 @@ __acquires(musb->lock)
        return handled;
 }
 
+static int ep0_send_ack(struct musb *musb)
+{
+       void __iomem *regs = musb->control_ep->regs;
+       u16 ackpend;
+
+       if (musb->ep0_state != MUSB_EP0_STAGE_RX &&
+           musb->ep0_state != MUSB_EP0_STAGE_STATUSIN)
+               return -EINVAL;
+
+       ackpend = MUSB_CSR0_P_DATAEND | MUSB_CSR0_P_SVDRXPKTRDY;
+
+       musb_ep_select(musb->mregs, 0);
+       musb_writew(regs, MUSB_CSR0, ackpend);
+
+       return 0;
+}
+
 /* we have an ep0out data packet
  * Context:  caller holds controller lock
  */
@@ -504,10 +521,13 @@ static void ep0_rxstate(struct musb *musb)
        if (req) {
                musb->ackpend = csr;
                musb_g_ep0_giveback(musb, req);
+               if (req->explicit_status)
+                       return;
                if (!musb->ackpend)
                        return;
                musb->ackpend = 0;
        }
+
        musb_ep_select(musb->mregs, 0);
        musb_writew(regs, MUSB_CSR0, csr);
 }
@@ -939,6 +959,9 @@ musb_g_ep0_queue(struct usb_ep *e, struct usb_request *r, 
gfp_t gfp_flags)
        case MUSB_EP0_STAGE_ACKWAIT:    /* zero-length data */
                status = 0;
                break;
+       case MUSB_EP0_STAGE_STATUSIN:
+               status = ep0_send_ack(musb);
+               goto cleanup;
        default:
                musb_dbg(musb, "ep0 request queued in state %d",
                                musb->ep0_state);
-- 
2.19.2

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