Adding ring size to index calculation is pointless, since index
will be masked with ring size - 1.
Suggested-by: David Laight <David.Laight@ACULAB.COM>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
        if (qcp_rd_p == tx_ring->qcp_rd_p)
                return;
 
-       todo = D_IDX(tx_ring, qcp_rd_p + tx_ring->cnt - tx_ring->qcp_rd_p);
+       todo = D_IDX(tx_ring, qcp_rd_p - tx_ring->qcp_rd_p);
 
        while (todo--) {
                idx = D_IDX(tx_ring, tx_ring->rd_p++);
        if (qcp_rd_p == tx_ring->qcp_rd_p)
                return true;
 
-       todo = D_IDX(tx_ring, qcp_rd_p + tx_ring->cnt - tx_ring->qcp_rd_p);
+       todo = D_IDX(tx_ring, qcp_rd_p - tx_ring->qcp_rd_p);
 
        done_all = todo <= NFP_NET_XDP_MAX_COMPLETE;
        todo = min(todo, NFP_NET_XDP_MAX_COMPLETE);