sfc: complete the next packet when we receive a timestamp

We now ignore the "completion" event when using tx queue timestamping,
and only pay attention to the two (high and low) timestamp events. The
NIC will send a pair of timestamp events for every packet transmitted.
The current firmware may merge the completion events, and it is possible
that future versions may reorder the completion and timestamp events.
As such the completion event is not useful.

Without this patch in place a merged completion event on a queue with
timestamping will cause a "spurious TX completion" error. This affects
SFN8000-series adapters.

Signed-off-by: Tom Zhao <tzhao@solarflare.com>
Acked-by: Martin Habets <mhabets@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 17 insertions, 15 deletions

diff --git a/drivers/net/ethernet/sfc/ef10.c b/drivers/net/ethernet/sfc/ef10.c
index 52113b7529d6..3f16bd807c6e 100644
--- a/drivers/net/ethernet/sfc/ef10.c
+++ b/drivers/net/ethernet/sfc/ef10.c
@@ -2853,11 +2853,24 @@ efx_ef10_handle_tx_event(struct efx_channel *channel, efx_qword_t *event)
 	}
 
 	/* Transmit timestamps are only available for 8XXX series. They result
-	 * in three events per packet. These occur in order, and are:
-	 *  - the normal completion event
+	 * in up to three events per packet. These occur in order, and are:
+	 *  - the normal completion event (may be omitted)
 	 *  - the low part of the timestamp
 	 *  - the high part of the timestamp
 	 *
+	 * It's possible for multiple completion events to appear before the
+	 * corresponding timestamps. So we can for example get:
+	 *  COMP N
+	 *  COMP N+1
+	 *  TS_LO N
+	 *  TS_HI N
+	 *  TS_LO N+1
+	 *  TS_HI N+1
+	 *
+	 * In addition it's also possible for the adjacent completions to be
+	 * merged, so we may not see COMP N above. As such, the completion
+	 * events are not very useful here.
+	 *
 	 * Each part of the timestamp is itself split across two 16 bit
 	 * fields in the event.
 	 */
@@ -2865,17 +2878,7 @@ efx_ef10_handle_tx_event(struct efx_channel *channel, efx_qword_t *event)
 
 	switch (tx_ev_type) {
 	case TX_TIMESTAMP_EVENT_TX_EV_COMPLETION:
-		/* In case of Queue flush or FLR, we might have received
-		 * the previous TX completion event but not the Timestamp
-		 * events.
-		 */
-		if (tx_queue->completed_desc_ptr != tx_queue->ptr_mask)
-			efx_xmit_done(tx_queue, tx_queue->completed_desc_ptr);
-
-		tx_ev_desc_ptr = EFX_QWORD_FIELD(*event,
-						 ESF_DZ_TX_DESCR_INDX);
-		tx_queue->completed_desc_ptr =
-					tx_ev_desc_ptr & tx_queue->ptr_mask;
+		/* Ignore this event - see above. */
 		break;
 
 	case TX_TIMESTAMP_EVENT_TX_EV_TSTAMP_LO:
@@ -2887,8 +2890,7 @@ efx_ef10_handle_tx_event(struct efx_channel *channel, efx_qword_t *event)
 		ts_part = efx_ef10_extract_event_ts(event);
 		tx_queue->completed_timestamp_major = ts_part;
 
-		efx_xmit_done(tx_queue, tx_queue->completed_desc_ptr);
-		tx_queue->completed_desc_ptr = tx_queue->ptr_mask;
+		efx_xmit_done_single(tx_queue);
 		break;
 
 	default: