sfc: Fix search for flush completion events

When flushing queues we disable normal interrupt and event handling and
poll event queue 0 looking for flush completions.  Unfortunately the
flush event polling loop fails to move past any other type of event.
This problem has not been observed in production hardware but appears to
be a possibility.
Signed-off-by: NBen Hutchings <bhutchings@solarflare.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/sfc/falcon.c

@@ -1187,31 +1187,29 @@ static void falcon_poll_flush_events(struct efx_nic *efx)
 	struct efx_channel *channel = &efx->channel[0];
 	struct efx_tx_queue *tx_queue;
 	struct efx_rx_queue *rx_queue;
-	unsigned int read_ptr, i;
+	unsigned int read_ptr = channel->eventq_read_ptr;
+	unsigned int end_ptr = (read_ptr - 1) & FALCON_EVQ_MASK;
 
-	read_ptr = channel->eventq_read_ptr;
-	for (i = 0; i < FALCON_EVQ_SIZE; ++i) {
+	do {
 		efx_qword_t *event = falcon_event(channel, read_ptr);
 		int ev_code, ev_sub_code, ev_queue;
 		bool ev_failed;
+
 		if (!falcon_event_present(event))
 			break;
 
 		ev_code = EFX_QWORD_FIELD(*event, EV_CODE);
-		if (ev_code != DRIVER_EV_DECODE)
-			continue;
-
 		ev_sub_code = EFX_QWORD_FIELD(*event, DRIVER_EV_SUB_CODE);
-		switch (ev_sub_code) {
-		case TX_DESCQ_FLS_DONE_EV_DECODE:
+		if (ev_code == DRIVER_EV_DECODE &&
+		    ev_sub_code == TX_DESCQ_FLS_DONE_EV_DECODE) {
 			ev_queue = EFX_QWORD_FIELD(*event,
 						   DRIVER_EV_TX_DESCQ_ID);
 			if (ev_queue < EFX_TX_QUEUE_COUNT) {
 				tx_queue = efx->tx_queue + ev_queue;
 				tx_queue->flushed = true;
 			}
-			break;
-		case RX_DESCQ_FLS_DONE_EV_DECODE:
+		} else if (ev_code == DRIVER_EV_DECODE &&
+			   ev_sub_code == RX_DESCQ_FLS_DONE_EV_DECODE) {
 			ev_queue = EFX_QWORD_FIELD(*event,
 						   DRIVER_EV_RX_DESCQ_ID);
 			ev_failed = EFX_QWORD_FIELD(*event,
@@ -1225,11 +1223,10 @@ static void falcon_poll_flush_events(struct efx_nic *efx)
 				else
 					rx_queue->flushed = true;
 			}
-			break;
 		}
 
 		read_ptr = (read_ptr + 1) & FALCON_EVQ_MASK;
-	}
+	} while (read_ptr != end_ptr);
 }
 
 /* Handle tx and rx flushes at the same time, since they run in