mlxsw: spectrum_trap: Introduce dummy group with thin policer

For "source traps" it is not possible to change HPKT action to discard.
But there is still need to disallow packets arriving to CPU as much as
possible. Handle this by introduction of a "dummy group". It has a
"thin" policer, which passes as less packets to CPU as possible. The
rest is going to be discarded there. The "dummy group" is to be used
later on by ACL trap (which is a "source trap").

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

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

@@ -5526,6 +5526,7 @@ enum mlxsw_reg_htgt_trap_group {
 
 enum mlxsw_reg_htgt_discard_trap_group {
 	MLXSW_REG_HTGT_DISCARD_TRAP_GROUP_BASE = MLXSW_REG_HTGT_TRAP_GROUP_MAX,
+	MLXSW_REG_HTGT_TRAP_GROUP_SP_DUMMY,
 	MLXSW_REG_HTGT_TRAP_GROUP_SP_L2_DISCARDS,
 	MLXSW_REG_HTGT_TRAP_GROUP_SP_L3_DISCARDS,
 	MLXSW_REG_HTGT_TRAP_GROUP_SP_TUNNEL_DISCARDS,

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

@@ -239,16 +239,36 @@ static const u16 mlxsw_sp_listener_devlink_map[] = {
 };
 
 #define MLXSW_SP_DISCARD_POLICER_ID	(MLXSW_REG_HTGT_TRAP_GROUP_MAX + 1)
+#define MLXSW_SP_THIN_POLICER_ID	(MLXSW_SP_DISCARD_POLICER_ID + 1)
 
 static int mlxsw_sp_trap_cpu_policers_set(struct mlxsw_sp *mlxsw_sp)
 {
 	char qpcr_pl[MLXSW_REG_QPCR_LEN];
+	int err;
 
 	mlxsw_reg_qpcr_pack(qpcr_pl, MLXSW_SP_DISCARD_POLICER_ID,
 			    MLXSW_REG_QPCR_IR_UNITS_M, false, 10 * 1024, 7);
+	err = mlxsw_reg_write(mlxsw_sp->core, MLXSW_REG(qpcr), qpcr_pl);
+	if (err)
+		return err;
+
+	/* The purpose of "thin" policer is to drop as many packets
+	 * as possible. The dummy group is using it.
+	 */
+	mlxsw_reg_qpcr_pack(qpcr_pl, MLXSW_SP_THIN_POLICER_ID,
+			    MLXSW_REG_QPCR_IR_UNITS_M, false, 1, 4);
 	return mlxsw_reg_write(mlxsw_sp->core, MLXSW_REG(qpcr), qpcr_pl);
 }
 
+static int mlxsw_sp_trap_dummy_group_init(struct mlxsw_sp *mlxsw_sp)
+{
+	char htgt_pl[MLXSW_REG_HTGT_LEN];
+
+	mlxsw_reg_htgt_pack(htgt_pl, MLXSW_REG_HTGT_TRAP_GROUP_SP_DUMMY,
+			    MLXSW_SP_THIN_POLICER_ID, 0, 1);
+	return mlxsw_reg_write(mlxsw_sp->core, MLXSW_REG(htgt), htgt_pl);
+}
+
 int mlxsw_sp_devlink_traps_init(struct mlxsw_sp *mlxsw_sp)
 {
 	struct devlink *devlink = priv_to_devlink(mlxsw_sp->core);
@@ -258,6 +278,10 @@ int mlxsw_sp_devlink_traps_init(struct mlxsw_sp *mlxsw_sp)
 	if (err)
 		return err;
 
+	err = mlxsw_sp_trap_dummy_group_init(mlxsw_sp);
+	if (err)
+		return err;
+
 	if (WARN_ON(ARRAY_SIZE(mlxsw_sp_listener_devlink_map) !=
 		    ARRAY_SIZE(mlxsw_sp_listeners_arr)))
 		return -EINVAL;