mlxsw: spectrum_matchall: Implement sampling using mirroring

Spectrum-2 and later ASICs support sampling of packets by mirroring to
the CPU with probability. There are several advantages compared to the
legacy dedicated sampling mechanism:

* Extra metadata per-packet: Egress port, egress traffic class, traffic
  class occupancy and end-to-end latency
* Ability to sample packets on egress / per-flow

Convert Spectrum-2 and later ASICs to perform sampling by mirroring to
the CPU with probability.

Subsequent patches will add support for egress / per-flow sampling and
expose the extra metadata.

Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlxsw/spectrum.h

@@ -238,6 +238,7 @@ struct mlxsw_sp_port_sample {
 	u32 trunc_size;
 	u32 rate;
 	bool truncate;
+	int span_id;	/* Relevant for Spectrum-2 onwards. */
 };
 
 struct mlxsw_sp_bridge_port;

drivers/net/ethernet/mellanox/mlxsw/spectrum_matchall.c

@@ -378,7 +378,60 @@ const struct mlxsw_sp_mall_ops mlxsw_sp1_mall_ops = {
 	.sample_del = mlxsw_sp1_mall_sample_del,
 };
 
+static int mlxsw_sp2_mall_sample_add(struct mlxsw_sp *mlxsw_sp,
+				     struct mlxsw_sp_port *mlxsw_sp_port,
+				     u32 rate)
+{
+	struct mlxsw_sp_span_trigger_parms trigger_parms = {};
+	struct mlxsw_sp_span_agent_parms agent_parms = {
+		.to_dev = NULL,	/* Mirror to CPU. */
+		.session_id = MLXSW_SP_SPAN_SESSION_ID_SAMPLING,
+	};
+	struct mlxsw_sp_port_sample *sample;
+	int err;
+
+	sample = rtnl_dereference(mlxsw_sp_port->sample);
+
+	err = mlxsw_sp_span_agent_get(mlxsw_sp, &sample->span_id, &agent_parms);
+	if (err)
+		return err;
+
+	err = mlxsw_sp_span_analyzed_port_get(mlxsw_sp_port, true);
+	if (err)
+		goto err_analyzed_port_get;
+
+	trigger_parms.span_id = sample->span_id;
+	trigger_parms.probability_rate = rate;
+	err = mlxsw_sp_span_agent_bind(mlxsw_sp, MLXSW_SP_SPAN_TRIGGER_INGRESS,
+				       mlxsw_sp_port, &trigger_parms);
+	if (err)
+		goto err_agent_bind;
+
+	return 0;
+
+err_agent_bind:
+	mlxsw_sp_span_analyzed_port_put(mlxsw_sp_port, true);
+err_analyzed_port_get:
+	mlxsw_sp_span_agent_put(mlxsw_sp, sample->span_id);
+	return err;
+}
+
+static void mlxsw_sp2_mall_sample_del(struct mlxsw_sp *mlxsw_sp,
+				      struct mlxsw_sp_port *mlxsw_sp_port)
+{
+	struct mlxsw_sp_span_trigger_parms trigger_parms = {};
+	struct mlxsw_sp_port_sample *sample;
+
+	sample = rtnl_dereference(mlxsw_sp_port->sample);
+
+	trigger_parms.span_id = sample->span_id;
+	mlxsw_sp_span_agent_unbind(mlxsw_sp, MLXSW_SP_SPAN_TRIGGER_INGRESS,
+				   mlxsw_sp_port, &trigger_parms);
+	mlxsw_sp_span_analyzed_port_put(mlxsw_sp_port, true);
+	mlxsw_sp_span_agent_put(mlxsw_sp, sample->span_id);
+}
+
 const struct mlxsw_sp_mall_ops mlxsw_sp2_mall_ops = {
-	.sample_add = mlxsw_sp1_mall_sample_add,
-	.sample_del = mlxsw_sp1_mall_sample_del,
+	.sample_add = mlxsw_sp2_mall_sample_add,
+	.sample_del = mlxsw_sp2_mall_sample_del,
 };

drivers/net/ethernet/mellanox/mlxsw/spectrum_span.h

@@ -21,6 +21,7 @@ struct mlxsw_sp_port;
  */
 enum mlxsw_sp_span_session_id {
 	MLXSW_SP_SPAN_SESSION_ID_BUFFER,
+	MLXSW_SP_SPAN_SESSION_ID_SAMPLING,
 
 	__MLXSW_SP_SPAN_SESSION_ID_MAX = 8,
 };

drivers/net/ethernet/mellanox/mlxsw/spectrum_trap.c

@@ -49,6 +49,8 @@ enum {
 #define MLXSW_SP_TRAP_METADATA DEVLINK_TRAP_METADATA_TYPE_F_IN_PORT
 
 enum {
+	/* Packet was mirrored from ingress. */
+	MLXSW_SP_MIRROR_REASON_INGRESS = 1,
 	/* Packet was early dropped. */
 	MLXSW_SP_MIRROR_REASON_INGRESS_WRED = 9,
 };
@@ -1753,6 +1755,7 @@ mlxsw_sp2_trap_group_items_arr[] = {
 		.group = DEVLINK_TRAP_GROUP_GENERIC(ACL_SAMPLE, 0),
 		.hw_group_id = MLXSW_REG_HTGT_TRAP_GROUP_SP_PKT_SAMPLE,
 		.priority = 0,
+		.fixed_policer = true,
 	},
 };
 
@@ -1769,8 +1772,9 @@ mlxsw_sp2_trap_items_arr[] = {
 		.trap = MLXSW_SP_TRAP_CONTROL(FLOW_ACTION_SAMPLE, ACL_SAMPLE,
 					      MIRROR),
 		.listeners_arr = {
-			MLXSW_RXL(mlxsw_sp_rx_sample_listener, PKT_SAMPLE,
-				  MIRROR_TO_CPU, false, SP_PKT_SAMPLE, DISCARD),
+			MLXSW_RXL_MIRROR(mlxsw_sp_rx_sample_listener, 1,
+					 SP_PKT_SAMPLE,
+					 MLXSW_SP_MIRROR_REASON_INGRESS),
 		},
 	},
 };