[S390] qdio: remove enhanced SIGA

HiperSocket devices only use one SBAL per qdio call without the enhanced SIGA
feature. Since that feature is currently not used remove it from the qdio code
so the compiler can generate better code for the HiperSocket outbound path.
While at it mark the SIGA error conditions as unlikely.

Signed-off-by: Jan Glauber <jang@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/cio/qdio.h

@@ -252,8 +252,6 @@ struct qdio_input_q {
 struct qdio_output_q {
 	/* PCIs are enabled for the queue */
 	int pci_out_enabled;
-	/* IQDIO: output multiple buffers (enhanced SIGA) */
-	int use_enh_siga;
 	/* timer to check for more outbound work */
 	struct timer_list timer;
 	/* used SBALs before tasklet schedule */

drivers/s390/cio/qdio_main.c

@@ -298,7 +298,7 @@ static inline int qdio_siga_sync(struct qdio_q *q, unsigned int output,
 	}
 
 	cc = do_siga_sync(schid, output, input, fc);
-	if (cc)
+	if (unlikely(cc))
 		DBF_ERROR("%4x SIGA-S:%2d", SCH_NO(q), cc);
 	return cc;
 }
@@ -328,9 +328,6 @@ static int qdio_siga_output(struct qdio_q *q, unsigned int *busy_bit)
 	u64 start_time = 0;
 	int cc;
 
-	if (q->u.out.use_enh_siga)
-		fc = 3;
-
 	if (is_qebsm(q)) {
 		schid = q->irq_ptr->sch_token;
 		fc |= QDIO_SIGA_QEBSM_FLAG;
@@ -339,7 +336,7 @@ again:
 	cc = do_siga_output(schid, q->mask, busy_bit, fc);
 
 	/* hipersocket busy condition */
-	if (*busy_bit) {
+	if (unlikely(*busy_bit)) {
 		WARN_ON(queue_type(q) != QDIO_IQDIO_QFMT || cc != 2);
 
 		if (!start_time) {
@@ -367,7 +364,7 @@ static inline int qdio_siga_input(struct qdio_q *q)
 	}
 
 	cc = do_siga_input(schid, q->mask, fc);
-	if (cc)
+	if (unlikely(cc))
 		DBF_ERROR("%4x SIGA-R:%2d", SCH_NO(q), cc);
 	return cc;
 }
@@ -1288,7 +1285,6 @@ int qdio_establish(struct qdio_initialize *init_data)
 	}
 
 	qdio_setup_ssqd_info(irq_ptr);
-	DBF_EVENT("qDmmwc:%2x", irq_ptr->ssqd_desc.mmwc);
 	DBF_EVENT("qib ac:%4x", irq_ptr->qib.ac);
 
 	/* qebsm is now setup if available, initialize buffer states */
@@ -1466,48 +1462,25 @@ static int handle_outbound(struct qdio_q *q, unsigned int callflags,
 	if (callflags & QDIO_FLAG_PCI_OUT) {
 		q->u.out.pci_out_enabled = 1;
 		qperf_inc(q, pci_request_int);
-	}
-	else
+	} else
 		q->u.out.pci_out_enabled = 0;
 
 	if (queue_type(q) == QDIO_IQDIO_QFMT) {
-		if (multicast_outbound(q))
+		/* One SIGA-W per buffer required for unicast HiperSockets. */
+		WARN_ON_ONCE(count > 1 && !multicast_outbound(q));
+
+		rc = qdio_kick_outbound_q(q);
+	} else if (unlikely(need_siga_sync(q))) {
+		rc = qdio_siga_sync_q(q);
+	} else {
+		/* try to fast requeue buffers */
+		get_buf_state(q, prev_buf(bufnr), &state, 0);
+		if (state != SLSB_CU_OUTPUT_PRIMED)
 			rc = qdio_kick_outbound_q(q);
 		else
-			if ((q->irq_ptr->ssqd_desc.mmwc > 1) &&
-			    (count > 1) &&
-			    (count <= q->irq_ptr->ssqd_desc.mmwc)) {
-				/* exploit enhanced SIGA */
-				q->u.out.use_enh_siga = 1;
-				rc = qdio_kick_outbound_q(q);
-			} else {
-				/*
-				* One siga-w per buffer required for unicast
-				* HiperSockets.
-				*/
-				q->u.out.use_enh_siga = 0;
-				while (count--) {
-					rc = qdio_kick_outbound_q(q);
-					if (rc)
-						goto out;
-				}
-			}
-		goto out;
+			qperf_inc(q, fast_requeue);
 	}
 
-	if (need_siga_sync(q)) {
-		qdio_siga_sync_q(q);
-		goto out;
-	}
-
-	/* try to fast requeue buffers */
-	get_buf_state(q, prev_buf(bufnr), &state, 0);
-	if (state != SLSB_CU_OUTPUT_PRIMED)
-		rc = qdio_kick_outbound_q(q);
-	else
-		qperf_inc(q, fast_requeue);
-
-out:
 	/* in case of SIGA errors we must process the error immediately */
 	if (used >= q->u.out.scan_threshold || rc)
 		tasklet_schedule(&q->tasklet);