bnxt_en: Improve RX doorbell sequence.

When both RX buffers and RX aggregation buffers have to be
replenished at the end of NAPI, post the RX aggregation buffers first
before RX buffers.  Otherwise, we may run into a situation where
there are only RX buffers without RX aggregation buffers for a split
second.  This will cause the hardware to abort the RX packet and
report buffer errors, which will cause unnecessary cleanup by the
driver.

Ringing the Aggregation ring doorbell first before the RX ring doorbell
will prevent some of these buffer errors.  Use the same sequence during
ring initialization as well.

Fixes: 697197e5 ("bnxt_en: Re-structure doorbells.")
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/broadcom/bnxt/bnxt.c

@@ -2021,9 +2021,9 @@ static void __bnxt_poll_work_done(struct bnxt *bp, struct bnxt_napi *bnapi)
 	if (bnapi->events & BNXT_RX_EVENT) {
 		struct bnxt_rx_ring_info *rxr = bnapi->rx_ring;
 
-		bnxt_db_write(bp, &rxr->rx_db, rxr->rx_prod);
 		if (bnapi->events & BNXT_AGG_EVENT)
 			bnxt_db_write(bp, &rxr->rx_agg_db, rxr->rx_agg_prod);
+		bnxt_db_write(bp, &rxr->rx_db, rxr->rx_prod);
 	}
 	bnapi->events = 0;
 }
@@ -5064,6 +5064,7 @@ static void bnxt_set_db(struct bnxt *bp, struct bnxt_db_info *db, u32 ring_type,
 
 static int bnxt_hwrm_ring_alloc(struct bnxt *bp)
 {
+	bool agg_rings = !!(bp->flags & BNXT_FLAG_AGG_RINGS);
 	int i, rc = 0;
 	u32 type;
 
@@ -5139,7 +5140,9 @@ static int bnxt_hwrm_ring_alloc(struct bnxt *bp)
 		if (rc)
 			goto err_out;
 		bnxt_set_db(bp, &rxr->rx_db, type, map_idx, ring->fw_ring_id);
-		bnxt_db_write(bp, &rxr->rx_db, rxr->rx_prod);
+		/* If we have agg rings, post agg buffers first. */
+		if (!agg_rings)
+			bnxt_db_write(bp, &rxr->rx_db, rxr->rx_prod);
 		bp->grp_info[map_idx].rx_fw_ring_id = ring->fw_ring_id;
 		if (bp->flags & BNXT_FLAG_CHIP_P5) {
 			struct bnxt_cp_ring_info *cpr = &bnapi->cp_ring;
@@ -5158,7 +5161,7 @@ static int bnxt_hwrm_ring_alloc(struct bnxt *bp)
 		}
 	}
 
-	if (bp->flags & BNXT_FLAG_AGG_RINGS) {
+	if (agg_rings) {
 		type = HWRM_RING_ALLOC_AGG;
 		for (i = 0; i < bp->rx_nr_rings; i++) {
 			struct bnxt_rx_ring_info *rxr = &bp->rx_ring[i];
@@ -5174,6 +5177,7 @@ static int bnxt_hwrm_ring_alloc(struct bnxt *bp)
 			bnxt_set_db(bp, &rxr->rx_agg_db, type, map_idx,
 				    ring->fw_ring_id);
 			bnxt_db_write(bp, &rxr->rx_agg_db, rxr->rx_agg_prod);
+			bnxt_db_write(bp, &rxr->rx_db, rxr->rx_prod);
 			bp->grp_info[grp_idx].agg_fw_ring_id = ring->fw_ring_id;
 		}
 	}