net: ena: add handling of llq max tx burst size

There is a maximum TX burst size that the ENA device can handle.
It is exposed by the device to the driver and the driver
needs to comply with it to avoid bugs.

In this commit we:
1. Add ena_com_is_doorbell_needed(), which calculates the number of
   llq entries that will be used to hold a packet, and will return
   true if they exceed the number of allowed entries in a burst.
   If the function returns true, a doorbell needs to be invoked
   to send this packet in the next burst.

2. Follow the available entries in the current burst:
   - Every doorbell a new burst begins
   - With each write of an llq entry, the available entries in the
     current burst are decreased by 1.

Signed-off-by: Arthur Kiyanovski <akiyano@amazon.com>
Signed-off-by: Sameeh Jubran <sameehj@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 0 deletions

diff --git a/drivers/net/ethernet/amazon/ena/ena_netdev.c b/drivers/net/ethernet/amazon/ena/ena_netdev.c
index 9c83642922c7..d2b82f917d3f 100644
--- a/drivers/net/ethernet/amazon/ena/ena_netdev.c
+++ b/drivers/net/ethernet/amazon/ena/ena_netdev.c
@@ -2172,6 +2172,13 @@ static netdev_tx_t ena_start_xmit(struct sk_buff *skb, struct net_device *dev)
 	/* set flags and meta data */
 	ena_tx_csum(&ena_tx_ctx, skb);
 
+	if (unlikely(ena_com_is_doorbell_needed(tx_ring->ena_com_io_sq, &ena_tx_ctx))) {
+		netif_dbg(adapter, tx_queued, dev,
+			  "llq tx max burst size of queue %d achieved, writing doorbell to send burst\n",
+			  qid);
+		ena_com_write_sq_doorbell(tx_ring->ena_com_io_sq);
+	}
+
 	/* prepare the packet's descriptors to dma engine */
 	rc = ena_com_prepare_tx(tx_ring->ena_com_io_sq, &ena_tx_ctx,
 				&nb_hw_desc);