sfc: Do not attempt to flush queues if DMA is disabled

efx_nic_fatal_interrupt() disables DMA before scheduling a reset.
After this, we need not and *cannot* flush queues.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

drivers/net/ethernet/sfc/efx.c

@@ -656,25 +656,30 @@ static void efx_stop_datapath(struct efx_nic *efx)
 	struct efx_channel *channel;
 	struct efx_tx_queue *tx_queue;
 	struct efx_rx_queue *rx_queue;
+	struct pci_dev *dev = efx->pci_dev;
 	int rc;
 
 	EFX_ASSERT_RESET_SERIALISED(efx);
 	BUG_ON(efx->port_enabled);
 
-	rc = efx_nic_flush_queues(efx);
-	if (rc && EFX_WORKAROUND_7803(efx)) {
-		/* Schedule a reset to recover from the flush failure. The
-		 * descriptor caches reference memory we're about to free,
-		 * but falcon_reconfigure_mac_wrapper() won't reconnect
-		 * the MACs because of the pending reset. */
-		netif_err(efx, drv, efx->net_dev,
-			  "Resetting to recover from flush failure\n");
-		efx_schedule_reset(efx, RESET_TYPE_ALL);
-	} else if (rc) {
-		netif_err(efx, drv, efx->net_dev, "failed to flush queues\n");
-	} else {
-		netif_dbg(efx, drv, efx->net_dev,
-			  "successfully flushed all queues\n");
+	/* Only perform flush if dma is enabled */
+	if (dev->is_busmaster) {
+		rc = efx_nic_flush_queues(efx);
+
+		if (rc && EFX_WORKAROUND_7803(efx)) {
+			/* Schedule a reset to recover from the flush failure. The
+			 * descriptor caches reference memory we're about to free,
+			 * but falcon_reconfigure_mac_wrapper() won't reconnect
+			 * the MACs because of the pending reset. */
+			netif_err(efx, drv, efx->net_dev,
+				  "Resetting to recover from flush failure\n");
+			efx_schedule_reset(efx, RESET_TYPE_ALL);
+		} else if (rc) {
+			netif_err(efx, drv, efx->net_dev, "failed to flush queues\n");
+		} else {
+			netif_dbg(efx, drv, efx->net_dev,
+				  "successfully flushed all queues\n");
+		}
 	}
 
 	efx_for_each_channel(channel, efx) {