net: ena: allow queue allocation backoff when low on memory

If there is not enough memory to allocate io queues the driver will
try to allocate smaller queues.

The backoff algorithm is as follows:

1. Try to allocate TX and RX and if successful.
1.1. return success

2. Divide by 2 the size of the larger of RX and TX queues (or both if their size is the same).

3. If TX or RX is smaller than 256
3.1. return failure.
4. else
4.1. go back to 1.

Also change the tx_queue_size, rx_queue_size field names in struct
adapter to requested_tx_queue_size and requested_rx_queue_size, and
use RX and TX queue 0 for actual queue sizes.
Explanation:
The original fields were useless as they were simply used to assign
values once from them to each of the queues in the adapter in ena_probe().
They could simply be deleted. However now that we have a backoff
feature, we have use for them. In case of backoff there is a difference
between the requested queue sizes and the actual sizes. Therefore there
is a need to save the requested queue size for future retries of queue
allocation (for example if allocation failed and then ifdown + ifup was
called we want to start the allocation from the original requested size of
the queues).

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, 4 insertions, 2 deletions

diff --git a/drivers/net/ethernet/amazon/ena/ena_netdev.h b/drivers/net/ethernet/amazon/ena/ena_netdev.h
index afd2769f1e6b..e8fe08cb7ecb 100644
--- a/drivers/net/ethernet/amazon/ena/ena_netdev.h
+++ b/drivers/net/ethernet/amazon/ena/ena_netdev.h
@@ -79,6 +79,8 @@
 #define ENA_BAR_MASK (BIT(ENA_REG_BAR) | BIT(ENA_MEM_BAR))
 
 #define ENA_DEFAULT_RING_SIZE	(1024)
+#define ENA_MIN_RING_SIZE	(256)
+
 
 #define ENA_TX_WAKEUP_THRESH		(MAX_SKB_FRAGS + 2)
 #define ENA_DEFAULT_RX_COPYBREAK	(256 - NET_IP_ALIGN)
@@ -331,8 +333,8 @@ struct ena_adapter {
 	u32 tx_usecs, rx_usecs; /* interrupt moderation */
 	u32 tx_frames, rx_frames; /* interrupt moderation */
 
-	u32 tx_ring_size;
-	u32 rx_ring_size;
+	u32 requested_tx_ring_size;
+	u32 requested_rx_ring_size;
 
 	u32 max_tx_ring_size;
 	u32 max_rx_ring_size;