octeon_ep: implement xmit_more in transmit

Add xmit_more handling in tx datapath for octeon_ep pf.
Signed-off-by: Shinas Rasheed <srasheed@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/marvell/octeon_ep/octep_config.h

@@ -15,7 +15,7 @@
 /* Tx Queue: maximum descriptors per ring */
 #define OCTEP_IQ_MAX_DESCRIPTORS    1024
 /* Minimum input (Tx) requests to be enqueued to ring doorbell */
-#define OCTEP_DB_MIN                1
+#define OCTEP_DB_MIN                8
 /* Packet threshold for Tx queue interrupt */
 #define OCTEP_IQ_INTR_THRESHOLD     0x0
 

drivers/net/ethernet/marvell/octeon_ep/octep_main.c

@@ -784,6 +784,13 @@ static inline int octep_iq_full_check(struct octep_iq *iq)
 	/* Stop the queue if unable to send */
 	netif_stop_subqueue(iq->netdev, iq->q_no);
 
+	/* Allow for pending updates in write index
+	 * from iq_process_completion in other cpus
+	 * to reflect, in case queue gets free
+	 * entries.
+	 */
+	smp_mb();
+
 	/* check again and restart the queue, in case NAPI has just freed
 	 * enough Tx ring entries.
 	 */
@@ -818,6 +825,7 @@ static netdev_tx_t octep_start_xmit(struct sk_buff *skb,
 	struct octep_iq *iq;
 	skb_frag_t *frag;
 	u16 nr_frags, si;
+	int xmit_more;
 	u16 q_no, wi;
 
 	if (skb_put_padto(skb, ETH_ZLEN))
@@ -830,10 +838,6 @@ static netdev_tx_t octep_start_xmit(struct sk_buff *skb,
 	}
 
 	iq = oct->iq[q_no];
-	if (octep_iq_full_check(iq)) {
-		iq->stats.tx_busy++;
-		return NETDEV_TX_BUSY;
-	}
 
 	shinfo = skb_shinfo(skb);
 	nr_frags = shinfo->nr_frags;
@@ -894,19 +898,33 @@ static netdev_tx_t octep_start_xmit(struct sk_buff *skb,
 		hw_desc->dptr = tx_buffer->sglist_dma;
 	}
 
-	netdev_tx_sent_queue(iq->netdev_q, skb->len);
+	xmit_more = netdev_xmit_more();
+
+	__netdev_tx_sent_queue(iq->netdev_q, skb->len, xmit_more);
+
 	skb_tx_timestamp(skb);
 	atomic_inc(&iq->instr_pending);
+	iq->fill_cnt++;
 	wi++;
 	if (wi == iq->max_count)
 		wi = 0;
 	iq->host_write_index = wi;
+
+	/* octep_iq_full_check stops the queue and returns
+	 * true if so, in case the queue has become full
+	 * by inserting current packet. If so, we can
+	 * go ahead and ring doorbell.
+	 */
+	if (!octep_iq_full_check(iq) && xmit_more &&
+	    iq->fill_cnt < iq->fill_threshold)
+		return NETDEV_TX_OK;
+
 	/* Flush the hw descriptor before writing to doorbell */
 	wmb();
-
-	/* Ring Doorbell to notify the NIC there is a new packet */
-	writel(1, iq->doorbell_reg);
-	iq->stats.instr_posted++;
+	/* Ring Doorbell to notify the NIC of new packets */
+	writel(iq->fill_cnt, iq->doorbell_reg);
+	iq->stats.instr_posted += iq->fill_cnt;
+	iq->fill_cnt = 0;
 	return NETDEV_TX_OK;
 
 dma_map_sg_err: