[PATCH 2/2] USB: gadget: update ci13xxx to work with g_ether

[Artem Leonenko <tikkeri@xxxxxxxxx>]

There is one nasty scenario when CI13xxx driver fails:
	a) two or more rx requests are queued (g_ether does that)
	b) rx request completed, interrupt fires and ci13xxx dequeues rq
	c) request complete() callback gets called and in turn it calls ep_queue()
		c1) in ep_queue() request gets added to the TAIL of the rx queue list
	d) ep gets primed with rq from (b)
	e) interrupt fires
	f) request gets popped from queue head for hw dequeue
	G) requets from queue head wasn't enqueued
		g1)  isr_tr_complete_low() doesn't
		enqueue more requests and it doesn't prime EP,
		rx traffic stalls

Solution:
	a) enque queued requests ASAP, i.e. before calling complete() callback.
	b) don't HW enqueue and prime endpoint with recently added request and
	use the oldest request in the queue.

Fixed issues:
	a) ep_queue() may return an error code despite request was successfully
	added to the queue (if _hardware_enqueue() fails)
	b) Added requests are always processed in LIFO order, even if they are
	added in complete() callback
	c) Finally more than two and more queued requests are processed
consistently,
	even if they were added in complete() callback

And as a part of the fix to make g_ether (and especially booting with
NFS root) I had
to increase NET_IP_ALIGN to mips32 natural value (4).

The fix was successfully tested on MIPS based SoC with 4KEc core and
CI13612 core. Board successfully boots with NFS root using g_ether
on ci13xxx udc

Signed-off-by: Artem Leonenko <tikkeri@xxxxxxxxx>
---
 drivers/usb/gadget/ci13xxx_udc.c |   15 ++++++++-------
 drivers/usb/gadget/u_ether.h     |    5 +++++
 2 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/drivers/usb/gadget/ci13xxx_udc.c
b/drivers/usb/gadget/ci13xxx_udc.c
index d788c7d..2c06cad 100644
--- a/drivers/usb/gadget/ci13xxx_udc.c
+++ b/drivers/usb/gadget/ci13xxx_udc.c
@@ -1789,18 +1789,17 @@ __acquires(mEp->lock)

 	dbg_done(_usb_addr(mEp), mReq->ptr->token, retval);

-	if (!mReq->req.no_interrupt && mReq->req.complete != NULL) {
-		spin_unlock(mEp->lock);
-		mReq->req.complete(&mEp->ep, &mReq->req);
-		spin_lock(mEp->lock);
-	}
-
 	if (!list_empty(&mEp->qh[mEp->dir].queue)) {
 		mReq = list_entry(mEp->qh[mEp->dir].queue.next,
 				  struct ci13xxx_req, queue);
 		_hardware_enqueue(mEp, mReq);
 	}

+	if (!mReq->req.no_interrupt && mReq->req.complete != NULL) {
+		spin_unlock(mEp->lock);
+		mReq->req.complete(&mEp->ep, &mReq->req);
+		spin_lock(mEp->lock);
+	}
  done:
 	return retval;
 }
@@ -2170,7 +2169,9 @@ static int ep_queue(struct usb_ep *ep, struct
usb_request *req,
 	mReq->req.actual = 0;
 	list_add_tail(&mReq->queue, &mEp->qh[mEp->dir].queue);

-	retval = _hardware_enqueue(mEp, mReq);
+	if (list_is_singular(&mEp->qh[mEp->dir].queue))
+		retval = _hardware_enqueue(mEp, mReq);
+
 	if (retval == -EALREADY || retval == -EBUSY) {
 		dbg_event(_usb_addr(mEp), "QUEUE", retval);
 		retval = 0;
diff --git a/drivers/usb/gadget/u_ether.h b/drivers/usb/gadget/u_ether.h
index 3c8c0c9..c4bb92e 100644
--- a/drivers/usb/gadget/u_ether.h
+++ b/drivers/usb/gadget/u_ether.h
@@ -23,6 +23,11 @@
 #ifndef __U_ETHER_H
 #define __U_ETHER_H

+#if defined(CONFIG_USB_GADGET_CI13XXX)
+#define NET_IP_ALIGN                    4
+#endif
+
+
 #include <linux/err.h>
 #include <linux/if_ether.h>
 #include <linux/usb/composite.h>
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