s390/qdio: enable drivers to poll for Output completions

While commit d36deae7 ("qdio: extend API to allow polling") enhanced
the qdio layer so that drivers can poll their Input Queues, we don't
have the corresponding infrastructure for Output Queues yet.

Factor out a helper that scans a single QDIO Queue, so that qeth can
implement TX NAPI on top of it.
While doing so, remove the duplicated tracking of the next-to-scan index
(q->first_to_check vs q->first_to_kick) in this code path.

qdio_handle_aobs() needs to move slightly upwards in the code hierarchy,
so that it's still called from the polling path.
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Acked-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

arch/s390/include/asm/qdio.h

@@ -416,6 +416,9 @@ extern int do_QDIO(struct ccw_device *, unsigned int, int, unsigned int,
 extern int qdio_start_irq(struct ccw_device *, int);
 extern int qdio_stop_irq(struct ccw_device *, int);
 extern int qdio_get_next_buffers(struct ccw_device *, int, int *, int *);
+extern int qdio_inspect_queue(struct ccw_device *cdev, unsigned int nr,
+			      bool is_input, unsigned int *bufnr,
+			      unsigned int *error);
 extern int qdio_shutdown(struct ccw_device *, int);
 extern int qdio_free(struct ccw_device *);
 extern int qdio_get_ssqd_desc(struct ccw_device *, struct qdio_ssqd_desc *);

drivers/s390/cio/qdio_main.c

@@ -647,8 +647,6 @@ static void qdio_kick_handler(struct qdio_q *q, unsigned int count)
 		qperf_inc(q, outbound_handler);
 		DBF_DEV_EVENT(DBF_INFO, q->irq_ptr, "koh: s:%02x c:%02x",
 			      start, count);
-		if (q->u.out.use_cq)
-			qdio_handle_aobs(q, start, count);
 	}
 
 	q->handler(q->irq_ptr->cdev, q->qdio_error, q->nr, start, count,
@@ -774,8 +772,11 @@ static inline int qdio_outbound_q_moved(struct qdio_q *q, unsigned int start)
 
 	count = get_outbound_buffer_frontier(q, start);
 
-	if (count)
+	if (count) {
 		DBF_DEV_EVENT(DBF_INFO, q->irq_ptr, "out moved:%1d", q->nr);
+		if (q->u.out.use_cq)
+			qdio_handle_aobs(q, start, count);
+	}
 
 	return count;
 }
@@ -1655,6 +1656,44 @@ int qdio_start_irq(struct ccw_device *cdev, int nr)
 }
 EXPORT_SYMBOL(qdio_start_irq);
 
+static int __qdio_inspect_queue(struct qdio_q *q, unsigned int *bufnr,
+				unsigned int *error)
+{
+	unsigned int start = q->first_to_check;
+	int count;
+
+	count = q->is_input_q ? qdio_inbound_q_moved(q, start) :
+				qdio_outbound_q_moved(q, start);
+	if (count == 0)
+		return 0;
+
+	*bufnr = start;
+	*error = q->qdio_error;
+
+	/* for the next time */
+	q->first_to_check = add_buf(start, count);
+	q->qdio_error = 0;
+
+	return count;
+}
+
+int qdio_inspect_queue(struct ccw_device *cdev, unsigned int nr, bool is_input,
+		       unsigned int *bufnr, unsigned int *error)
+{
+	struct qdio_irq *irq_ptr = cdev->private->qdio_data;
+	struct qdio_q *q;
+
+	if (!irq_ptr)
+		return -ENODEV;
+	q = is_input ? irq_ptr->input_qs[nr] : irq_ptr->output_qs[nr];
+
+	if (need_siga_sync(q))
+		qdio_siga_sync_q(q);
+
+	return __qdio_inspect_queue(q, bufnr, error);
+}
+EXPORT_SYMBOL_GPL(qdio_inspect_queue);
+
 /**
  * qdio_get_next_buffers - process input buffers
  * @cdev: associated ccw_device for the qdio subchannel
@@ -1672,13 +1711,10 @@ int qdio_get_next_buffers(struct ccw_device *cdev, int nr, int *bufnr,
 {
 	struct qdio_q *q;
 	struct qdio_irq *irq_ptr = cdev->private->qdio_data;
-	unsigned int start;
-	int count;
 
 	if (!irq_ptr)
 		return -ENODEV;
 	q = irq_ptr->input_qs[nr];
-	start = q->first_to_check;
 
 	/*
 	 * Cannot rely on automatic sync after interrupt since queues may
@@ -1689,25 +1725,11 @@ int qdio_get_next_buffers(struct ccw_device *cdev, int nr, int *bufnr,
 
 	qdio_check_outbound_pci_queues(irq_ptr);
 
-	count = qdio_inbound_q_moved(q, start);
-	if (count == 0)
-		return 0;
-
-	start = add_buf(start, count);
-	q->first_to_check = start;
-
 	/* Note: upper-layer MUST stop processing immediately here ... */
 	if (unlikely(q->irq_ptr->state != QDIO_IRQ_STATE_ACTIVE))
 		return -EIO;
 
-	*bufnr = q->first_to_kick;
-	*error = q->qdio_error;
-
-	/* for the next time */
-	q->first_to_kick = add_buf(q->first_to_kick, count);
-	q->qdio_error = 0;
-
-	return count;
+	return __qdio_inspect_queue(q, bufnr, error);
 }
 EXPORT_SYMBOL(qdio_get_next_buffers);