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, 11 insertions, 17 deletions

diff --git a/drivers/net/ethernet/amazon/ena/ena_eth_com.c b/drivers/net/ethernet/amazon/ena/ena_eth_com.c
index f6c2d3855be8..cad2b572808e 100644
--- a/drivers/net/ethernet/amazon/ena/ena_eth_com.c
+++ b/drivers/net/ethernet/amazon/ena/ena_eth_com.c
@@ -82,6 +82,17 @@ static inline int ena_com_write_bounce_buffer_to_dev(struct ena_com_io_sq *io_sq
 	dst_tail_mask = io_sq->tail & (io_sq->q_depth - 1);
 	dst_offset = dst_tail_mask * llq_info->desc_list_entry_size;
 
+	if (is_llq_max_tx_burst_exists(io_sq)) {
+		if (unlikely(!io_sq->entries_in_tx_burst_left)) {
+			pr_err("Error: trying to send more packets than tx burst allows\n");
+			return -ENOSPC;
+		}
+
+		io_sq->entries_in_tx_burst_left--;
+		pr_debug("decreasing entries_in_tx_burst_left of queue %d to %d\n",
+			 io_sq->qid, io_sq->entries_in_tx_burst_left);
+	}
+
 	/* Make sure everything was written into the bounce buffer before
 	 * writing the bounce buffer to the device
 	 */
@@ -274,23 +285,6 @@ static inline u16 ena_com_cdesc_rx_pkt_get(struct ena_com_io_cq *io_cq,
 	return count;
 }
 
-static inline bool ena_com_meta_desc_changed(struct ena_com_io_sq *io_sq,
-					     struct ena_com_tx_ctx *ena_tx_ctx)
-{
-	int rc;
-
-	if (ena_tx_ctx->meta_valid) {
-		rc = memcmp(&io_sq->cached_tx_meta,
-			    &ena_tx_ctx->ena_meta,
-			    sizeof(struct ena_com_tx_meta));
-
-		if (unlikely(rc != 0))
-			return true;
-	}
-
-	return false;
-}
-
 static inline int ena_com_create_and_store_tx_meta_desc(struct ena_com_io_sq *io_sq,
 							struct ena_com_tx_ctx *ena_tx_ctx)
 {