s390/qdio: remove internal polling in non-thinint path

For non-thinint devices in LPAR, qdio polls an idle Input Queue for a
little while to catch more work. But platform support for thinints has
been around practically _forever_ by now, so this micro-optimization is
seeing 0 actual use. Remove it to reduce the overall complexity of the
hot path.

In the meantime we also grew support for driver-level polling
(eg. NAPI in qeth), so it's quite questionable how useful this would
actually be on current kernels.

Signed-off-by: Julian Wiedmann <[email protected]>
Signed-off-by: Heiko Carstens <[email protected]>

Author: julianwiedmann

drivers/s390/cio/qdio.h

@@ -15,7 +15,6 @@
 #define QDIO_BUSY_BIT_PATIENCE		(100 << 12)	/* 100 microseconds */
 #define QDIO_BUSY_BIT_RETRY_DELAY	10		/* 10 milliseconds */
 #define QDIO_BUSY_BIT_RETRIES		1000		/* = 10s retry time */
-#define QDIO_INPUT_THRESHOLD		(500 << 12)	/* 500 microseconds */
 
 enum qdio_irq_states {
 	QDIO_IRQ_STATE_INACTIVE,
@@ -181,8 +180,6 @@ struct qdio_input_q {
 	/* Batch of SBALs that we processed while polling the queue: */
 	unsigned int batch_start;
 	unsigned int batch_count;
-	/* last time of noticing incoming data */
-	u64 timestamp;
 };
 
 struct qdio_output_q {

drivers/s390/cio/qdio_main.c

@@ -510,14 +510,7 @@ static int get_inbound_buffer_frontier(struct qdio_q *q, unsigned int start)
 
 static int qdio_inbound_q_moved(struct qdio_q *q, unsigned int start)
 {
-	int count;
-
-	count = get_inbound_buffer_frontier(q, start);
-
-	if (count && !is_thinint_irq(q->irq_ptr) && MACHINE_IS_LPAR)
-		q->u.in.timestamp = get_tod_clock();
-
-	return count;
+	return get_inbound_buffer_frontier(q, start);
 }
 
 static inline int qdio_inbound_q_done(struct qdio_q *q, unsigned int start)
@@ -535,22 +528,7 @@ static inline int qdio_inbound_q_done(struct qdio_q *q, unsigned int start)
 		/* more work coming */
 		return 0;
 
-	if (is_thinint_irq(q->irq_ptr))
-		return 1;
-
-	/* don't poll under z/VM */
-	if (MACHINE_IS_VM)
-		return 1;
-
-	/*
-	 * At this point we know, that inbound first_to_check
-	 * has (probably) not moved (see qdio_inbound_processing).
-	 */
-	if (get_tod_clock_fast() > q->u.in.timestamp + QDIO_INPUT_THRESHOLD) {
-		DBF_DEV_EVENT(DBF_INFO, q->irq_ptr, "in done:%02x", start);
-		return 1;
-	} else
-		return 0;
+	return 1;
 }
 
 static inline void qdio_handle_aobs(struct qdio_q *q, int start, int count)