sfc: Skip RX end-of-batch work on channels without an RX queue

The code in efx_process_channel() to update the RX queue after each
batch of RX completions works out as a no-op on a TX-only channel
where the RX queue structure is set to all-zeroes, but
(1) efx_channel_get_rx_queue() will BUG() if DEBUG is defined, and
(2) it's a waste of time.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

1 files changed, 11 insertions, 10 deletions

diff --git a/drivers/net/ethernet/sfc/efx.c b/drivers/net/ethernet/sfc/efx.c
index 952d0bf7695a..b7cf9f0108ed 100644
--- a/drivers/net/ethernet/sfc/efx.c
+++ b/drivers/net/ethernet/sfc/efx.c
@@ -224,19 +224,20 @@ static int efx_process_channel(struct efx_channel *channel, int budget)
                 return 0;
 
         spent = efx_nic_process_eventq(channel, budget);
-        if (spent == 0)
-                return 0;
+        if (spent && efx_channel_has_rx_queue(channel)) {
+                struct efx_rx_queue *rx_queue =
+                        efx_channel_get_rx_queue(channel);
+
+                /* Deliver last RX packet. */
+                if (channel->rx_pkt) {
+                        __efx_rx_packet(channel, channel->rx_pkt);
+                        channel->rx_pkt = NULL;
+                }
 
-        /* Deliver last RX packet. */
-        if (channel->rx_pkt) {
-                __efx_rx_packet(channel, channel->rx_pkt);
-                channel->rx_pkt = NULL;
+                efx_rx_strategy(channel);
+                efx_fast_push_rx_descriptors(rx_queue);
         }
 
-        efx_rx_strategy(channel);
-
-        efx_fast_push_rx_descriptors(efx_channel_get_rx_queue(channel));
-
         return spent;
 }