sfc: add ability for an RXQ to grant credits on refill

EF100 hardware streams MAE counter updates to the driver over a dedicated
 RX queue; however, the MCPU is not able to detect when RX buffers have
 been posted to the ring.  Thus, the driver must call
 MC_CMD_MAE_COUNTERS_STREAM_GIVE_CREDITS; this patch adds the
 infrastructure to support that to the core RXQ handling code.
Signed-off-by: Edward Cree <ecree.xilinx@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/sfc/ef100_rx.c

@@ -183,24 +183,32 @@ void efx_ef100_ev_rx(struct efx_channel *channel, const efx_qword_t *p_event)
 
 void ef100_rx_write(struct efx_rx_queue *rx_queue)
 {
+	unsigned int notified_count = rx_queue->notified_count;
 	struct efx_rx_buffer *rx_buf;
 	unsigned int idx;
 	efx_qword_t *rxd;
 	efx_dword_t rxdb;
 
-	while (rx_queue->notified_count != rx_queue->added_count) {
-		idx = rx_queue->notified_count & rx_queue->ptr_mask;
+	while (notified_count != rx_queue->added_count) {
+		idx = notified_count & rx_queue->ptr_mask;
 		rx_buf = efx_rx_buffer(rx_queue, idx);
 		rxd = efx_rx_desc(rx_queue, idx);
 
 		EFX_POPULATE_QWORD_1(*rxd, ESF_GZ_RX_BUF_ADDR, rx_buf->dma_addr);
 
-		++rx_queue->notified_count;
+		++notified_count;
 	}
+	if (notified_count == rx_queue->notified_count)
+		return;
 
 	wmb();
 	EFX_POPULATE_DWORD_1(rxdb, ERF_GZ_RX_RING_PIDX,
 			     rx_queue->added_count & rx_queue->ptr_mask);
 	efx_writed_page(rx_queue->efx, &rxdb,
 			ER_GZ_RX_RING_DOORBELL, efx_rx_queue_index(rx_queue));
+	if (rx_queue->grant_credits)
+		wmb();
+	rx_queue->notified_count = notified_count;
+	if (rx_queue->grant_credits)
+		schedule_work(&rx_queue->grant_work);
 }

drivers/net/ethernet/sfc/net_driver.h

@@ -363,8 +363,12 @@ struct efx_rx_page_state {
  * @refill_enabled: Enable refill whenever fill level is low
  * @flush_pending: Set when a RX flush is pending. Has the same lifetime as
  *	@rxq_flush_pending.
+ * @grant_credits: Posted RX descriptors need to be granted to the MAE with
+ *	%MC_CMD_MAE_COUNTERS_STREAM_GIVE_CREDITS.  For %EFX_EXTRA_CHANNEL_TC,
+ *	and only supported on EF100.
  * @added_count: Number of buffers added to the receive queue.
  * @notified_count: Number of buffers given to NIC (<= @added_count).
+ * @granted_count: Number of buffers granted to the MAE (<= @notified_count).
  * @removed_count: Number of buffers removed from the receive queue.
  * @scatter_n: Used by NIC specific receive code.
  * @scatter_len: Used by NIC specific receive code.
@@ -385,6 +389,7 @@ struct efx_rx_page_state {
  *	refill was triggered.
  * @recycle_count: RX buffer recycle counter.
  * @slow_fill: Timer used to defer efx_nic_generate_fill_event().
+ * @grant_work: workitem used to grant credits to the MAE if @grant_credits
  * @xdp_rxq_info: XDP specific RX queue information.
  * @xdp_rxq_info_valid: Is xdp_rxq_info valid data?.
  */
@@ -396,9 +401,11 @@ struct efx_rx_queue {
 	unsigned int ptr_mask;
 	bool refill_enabled;
 	bool flush_pending;
+	bool grant_credits;
 
 	unsigned int added_count;
 	unsigned int notified_count;
+	unsigned int granted_count;
 	unsigned int removed_count;
 	unsigned int scatter_n;
 	unsigned int scatter_len;
@@ -416,6 +423,7 @@ struct efx_rx_queue {
 	unsigned int recycle_count;
 	struct timer_list slow_fill;
 	unsigned int slow_fill_count;
+	struct work_struct grant_work;
 	/* Statistics to supplement MAC stats */
 	unsigned long rx_packets;
 	struct xdp_rxq_info xdp_rxq_info;

drivers/net/ethernet/sfc/rx_common.c

@@ -229,6 +229,7 @@ void efx_init_rx_queue(struct efx_rx_queue *rx_queue)
 	/* Initialise ptr fields */
 	rx_queue->added_count = 0;
 	rx_queue->notified_count = 0;
+	rx_queue->granted_count = 0;
 	rx_queue->removed_count = 0;
 	rx_queue->min_fill = -1U;
 	efx_init_rx_recycle_ring(rx_queue);
@@ -281,6 +282,8 @@ void efx_fini_rx_queue(struct efx_rx_queue *rx_queue)
 		  "shutting down RX queue %d\n", efx_rx_queue_index(rx_queue));
 
 	del_timer_sync(&rx_queue->slow_fill);
+	if (rx_queue->grant_credits)
+		flush_work(&rx_queue->grant_work);
 
 	/* Release RX buffers from the current read ptr to the write ptr */
 	if (rx_queue->buffer) {