s390/qdio: extend polling support to multiple queues

When the support for polling drivers was initially added, it only
considered Input Queue 0. But as QDIO interrupts are actually for the
full device and not a single queue, this doesn't really fit for
configurations where multiple Input Queues are used.

Rework the qdio code so that interrupts for a polling driver are not
split up into actions for each queue. Instead deliver the interrupt as
a single event, and let the driver decide which queue needs what action.

When re-enabling the QDIO interrupt via qdio_start_irq(), this means
that the qdio code needs to
(1) put _all_ eligible queues back into a state where they raise IRQs,
(2) and afterwards check _all_ eligible queues for new work to bridge
    the race window.

On the qeth side of things (as the only qdio polling driver), we can now
add CQ polling support to the main NAPI poll routine. It doesn't consume
NAPI budget, and to avoid hogging the CPU we yield control after
completing one full queue worth of buffers.
The subsequent qdio_start_irq() will check for any additional work, and
have us re-schedule the NAPI instance accordingly.

Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 17 insertions, 21 deletions

diff --git a/drivers/s390/cio/qdio_thinint.c b/drivers/s390/cio/qdio_thinint.c
index 7c4e4ec08a12..8f315c53de23 100644
--- a/drivers/s390/cio/qdio_thinint.c
+++ b/drivers/s390/cio/qdio_thinint.c
@@ -135,28 +135,24 @@ static inline void tiqdio_call_inq_handlers(struct qdio_irq *irq)
 	    has_multiple_inq_on_dsci(irq))
 		xchg(irq->dsci, 0);
 
+	if (irq->irq_poll) {
+		if (!test_and_set_bit(QDIO_IRQ_DISABLED, &irq->poll_state))
+			irq->irq_poll(irq->cdev, irq->int_parm);
+		else
+			QDIO_PERF_STAT_INC(irq, int_discarded);
+
+		return;
+	}
+
 	for_each_input_queue(irq, q, i) {
-		if (q->u.in.queue_start_poll) {
-			/* skip if polling is enabled or already in work */
-			if (test_and_set_bit(QDIO_QUEUE_IRQS_DISABLED,
-					     &q->u.in.queue_irq_state)) {
-				QDIO_PERF_STAT_INC(irq, int_discarded);
-				continue;
-			}
-
-			/* avoid dsci clear here, done after processing */
-			q->u.in.queue_start_poll(irq->cdev, q->nr,
-						 irq->int_parm);
-		} else {
-			if (!shared_ind(irq))
-				xchg(irq->dsci, 0);
-
-			/*
-			 * Call inbound processing but not directly
-			 * since that could starve other thinint queues.
-			 */
-			tasklet_schedule(&q->tasklet);
-		}
+		if (!shared_ind(irq))
+			xchg(irq->dsci, 0);
+
+		/*
+		 * Call inbound processing but not directly
+		 * since that could starve other thinint queues.
+		 */
+		tasklet_schedule(&q->tasklet);
 	}
 }