s390/qdio: fine-tune the queue sync

Push the sync check from qdio_inspect_queue() down into the two
get_*_buffer_frontier() code paths, where we actually need the sync to
look at the current queue state. This lets us avoid the check when we
know that there is no work on the queue (ie. when q->nr_buf_used is 0).

While at it introduce the qdio_sync_*_queue() helpers, so that we can
avoid the branch on q->is_input_q when we already know the queue type.
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Reviewed-by: Benjamin Block <bblock@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

drivers/s390/cio/qdio_main.c

@@ -303,12 +303,22 @@ static inline int qdio_siga_sync(struct qdio_q *q, unsigned int output,
 	return (cc) ? -EIO : 0;
 }
 
+static inline int qdio_sync_input_queue(struct qdio_q *q)
+{
+	return qdio_siga_sync(q, 0, q->mask);
+}
+
+static inline int qdio_sync_output_queue(struct qdio_q *q)
+{
+	return qdio_siga_sync(q, q->mask, 0);
+}
+
 static inline int qdio_siga_sync_q(struct qdio_q *q)
 {
 	if (q->is_input_q)
-		return qdio_siga_sync(q, 0, q->mask);
+		return qdio_sync_input_queue(q);
 	else
-		return qdio_siga_sync(q, q->mask, 0);
+		return qdio_sync_output_queue(q);
 }
 
 static int qdio_siga_output(struct qdio_q *q, unsigned int count,
@@ -442,10 +452,9 @@ static int get_inbound_buffer_frontier(struct qdio_q *q, unsigned int start,
 	if (!count)
 		return 0;
 
-	/*
-	 * No siga sync here, as a PCI or we after a thin interrupt
-	 * already sync'ed the queues.
-	 */
+	if (qdio_need_siga_sync(q->irq_ptr))
+		qdio_sync_input_queue(q);
+
 	count = get_buf_states(q, start, &state, count, 1);
 	if (!count)
 		return 0;
@@ -498,7 +507,7 @@ static inline int qdio_inbound_q_done(struct qdio_q *q, unsigned int start)
 		return 1;
 
 	if (qdio_need_siga_sync(q->irq_ptr))
-		qdio_siga_sync_q(q);
+		qdio_sync_input_queue(q);
 	get_buf_state(q, start, &state, 0);
 
 	if (state == SLSB_P_INPUT_PRIMED || state == SLSB_P_INPUT_ERROR)
@@ -520,6 +529,9 @@ static int get_outbound_buffer_frontier(struct qdio_q *q, unsigned int start,
 	if (!count)
 		return 0;
 
+	if (qdio_need_siga_sync(q->irq_ptr))
+		qdio_sync_output_queue(q);
+
 	count = get_buf_states(q, start, &state, count, 0);
 	if (!count)
 		return 0;
@@ -1160,7 +1172,7 @@ static int handle_outbound(struct qdio_q *q, unsigned int bufnr, unsigned int co
 		WARN_ON_ONCE(!IS_ALIGNED(phys_aob, 256));
 		rc = qdio_kick_outbound_q(q, count, phys_aob);
 	} else if (qdio_need_siga_sync(q->irq_ptr)) {
-		rc = qdio_siga_sync_q(q);
+		rc = qdio_sync_output_queue(q);
 	} else if (count < QDIO_MAX_BUFFERS_PER_Q &&
 		   get_buf_state(q, prev_buf(bufnr), &state, 0) > 0 &&
 		   state == SLSB_CU_OUTPUT_PRIMED) {
@@ -1283,9 +1295,6 @@ int qdio_inspect_queue(struct ccw_device *cdev, unsigned int nr, bool is_input,
 		return -ENODEV;
 	q = is_input ? irq_ptr->input_qs[nr] : irq_ptr->output_qs[nr];
 
-	if (qdio_need_siga_sync(irq_ptr))
-		qdio_siga_sync_q(q);
-
 	return __qdio_inspect_queue(q, bufnr, error);
 }
 EXPORT_SYMBOL_GPL(qdio_inspect_queue);