sfc: Add TX queues for high-priority traffic

Implement the ndo_setup_tc() operation with 2 traffic classes.

Current Solarstorm controllers do not implement TX queue priority, but
they do allow queues to be 'paced' with an enforced delay between
packets.  Paced and unpaced queues are scheduled in round-robin within
two separate hardware bins (paced queues with a large delay may be
placed into a third bin temporarily, but we won't use that).  If there
are queues in both bins, the TX scheduler will alternate between them.

If we make high-priority queues unpaced and best-effort queues paced,
and high-priority queues are mostly empty, a single high-priority queue
can then instantly take 50% of the packet rate regardless of how many
of the best-effort queues have descriptors outstanding.

We do not actually want an enforced delay between packets on best-
effort queues, so we set the pace value to a reserved value that
actually results in a delay of 0.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

1 files changed, 23 insertions, 6 deletions

diff --git a/drivers/net/sfc/net_driver.h b/drivers/net/sfc/net_driver.h
index 77b7ce451519..96e22ad34970 100644
--- a/drivers/net/sfc/net_driver.h
+++ b/drivers/net/sfc/net_driver.h
@@ -63,10 +63,12 @@
 /* Checksum generation is a per-queue option in hardware, so each
  * queue visible to the networking core is backed by two hardware TX
  * queues. */
-#define EFX_MAX_CORE_TX_QUEUES	EFX_MAX_CHANNELS
-#define EFX_TXQ_TYPE_OFFLOAD	1
-#define EFX_TXQ_TYPES		2
-#define EFX_MAX_TX_QUEUES	(EFX_TXQ_TYPES * EFX_MAX_CORE_TX_QUEUES)
+#define EFX_MAX_TX_TC		2
+#define EFX_MAX_CORE_TX_QUEUES	(EFX_MAX_TX_TC * EFX_MAX_CHANNELS)
+#define EFX_TXQ_TYPE_OFFLOAD	1	/* flag */
+#define EFX_TXQ_TYPE_HIGHPRI	2	/* flag */
+#define EFX_TXQ_TYPES		4
+#define EFX_MAX_TX_QUEUES	(EFX_TXQ_TYPES * EFX_MAX_CHANNELS)
 
 /**
  * struct efx_special_buffer - An Efx special buffer
@@ -140,6 +142,7 @@ struct efx_tx_buffer {
  * @buffer: The software buffer ring
  * @txd: The hardware descriptor ring
  * @ptr_mask: The size of the ring minus 1.
+ * @initialised: Has hardware queue been initialised?
  * @flushed: Used when handling queue flushing
  * @read_count: Current read pointer.
  *	This is the number of buffers that have been removed from both rings.
@@ -182,6 +185,7 @@ struct efx_tx_queue {
 	struct efx_tx_buffer *buffer;
 	struct efx_special_buffer txd;
 	unsigned int ptr_mask;
+	bool initialised;
 	enum efx_flush_state flushed;
 
 	/* Members used mainly on the completion path */
@@ -377,7 +381,7 @@ struct efx_channel {
 	bool rx_pkt_csummed;
 
 	struct efx_rx_queue rx_queue;
-	struct efx_tx_queue tx_queue[2];
+	struct efx_tx_queue tx_queue[EFX_TXQ_TYPES];
 };
 
 enum efx_led_mode {
@@ -952,15 +956,28 @@ efx_channel_get_tx_queue(struct efx_channel *channel, unsigned type)
 	return &channel->tx_queue[type];
 }
 
+static inline bool efx_tx_queue_used(struct efx_tx_queue *tx_queue)
+{
+	return !(tx_queue->efx->net_dev->num_tc < 2 &&
+		 tx_queue->queue & EFX_TXQ_TYPE_HIGHPRI);
+}
+
 /* Iterate over all TX queues belonging to a channel */
 #define efx_for_each_channel_tx_queue(_tx_queue, _channel)		\
 	if (!efx_channel_has_tx_queues(_channel))			\
 		;							\
 	else								\
 		for (_tx_queue = (_channel)->tx_queue;			\
-		     _tx_queue < (_channel)->tx_queue + EFX_TXQ_TYPES;	\
+		     _tx_queue < (_channel)->tx_queue + EFX_TXQ_TYPES && \
+			     efx_tx_queue_used(_tx_queue);		\
 		     _tx_queue++)
 
+/* Iterate over all possible TX queues belonging to a channel */
+#define efx_for_each_possible_channel_tx_queue(_tx_queue, _channel)	\
+	for (_tx_queue = (_channel)->tx_queue;				\
+	     _tx_queue < (_channel)->tx_queue + EFX_TXQ_TYPES;		\
+	     _tx_queue++)
+
 static inline struct efx_rx_queue *
 efx_get_rx_queue(struct efx_nic *efx, unsigned index)
 {