sfc: add start and stop methods to channels

The TC extra channel needs to do extra work in efx_{start,stop}_channels()
 to start/stop MAE counter streaming from the hardware.  Add callbacks for
 it to implement.
Signed-off-by: Edward Cree <ecree.xilinx@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/sfc/efx_channels.c

@@ -1119,6 +1119,8 @@ void efx_start_channels(struct efx_nic *efx)
 	struct efx_channel *channel;
 
 	efx_for_each_channel_rev(channel, efx) {
+		if (channel->type->start)
+			channel->type->start(channel);
 		efx_for_each_channel_tx_queue(tx_queue, channel) {
 			efx_init_tx_queue(tx_queue);
 			atomic_inc(&efx->active_queues);
@@ -1143,8 +1145,13 @@ void efx_stop_channels(struct efx_nic *efx)
 	struct efx_channel *channel;
 	int rc = 0;
 
-	/* Stop RX refill */
+	/* Stop special channels and RX refill.
+	 * The channel's stop has to be called first, since it might wait
+	 * for a sentinel RX to indicate the channel has fully drained.
+	 */
 	efx_for_each_channel(channel, efx) {
+		if (channel->type->stop)
+			channel->type->stop(channel);
 		efx_for_each_channel_rx_queue(rx_queue, channel)
 			rx_queue->refill_enabled = false;
 	}

drivers/net/ethernet/sfc/net_driver.h

@@ -585,6 +585,8 @@ struct efx_msi_context {
  * struct efx_channel_type - distinguishes traffic and extra channels
  * @handle_no_channel: Handle failure to allocate an extra channel
  * @pre_probe: Set up extra state prior to initialisation
+ * @start: called early in efx_start_channels()
+ * @stop: called early in efx_stop_channels()
  * @post_remove: Tear down extra state after finalisation, if allocated.
  *	May be called on channels that have not been probed.
  * @get_name: Generate the channel's name (used for its IRQ handler)
@@ -601,6 +603,8 @@ struct efx_msi_context {
 struct efx_channel_type {
 	void (*handle_no_channel)(struct efx_nic *);
 	int (*pre_probe)(struct efx_channel *);
+	int (*start)(struct efx_channel *);
+	void (*stop)(struct efx_channel *);
 	void (*post_remove)(struct efx_channel *);
 	void (*get_name)(struct efx_channel *, char *buf, size_t len);
 	struct efx_channel *(*copy)(const struct efx_channel *);