net/mlx5e: Fix a bug in turning off FEC policy in unsupported speeds

Some speeds don't support turning FEC policy off. In case a requested
FEC policy is not supported for a speed (including current speed), its new
FEC policy would be:
	no FEC - if disabling FEC is supported for that speed
	unchanged - else

Fixes: 2095b264 ("net/mlx5e: Add port FEC get/set functions")
Signed-off-by: Shay Agroskin <shayag@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

drivers/net/ethernet/mellanox/mlx5/core/en/port.c

@@ -394,12 +394,12 @@ int mlx5e_get_fec_mode(struct mlx5_core_dev *dev, u32 *fec_mode_active,
 
 int mlx5e_set_fec_mode(struct mlx5_core_dev *dev, u8 fec_policy)
 {
+	u8 fec_policy_nofec = BIT(MLX5E_FEC_NOFEC);
 	bool fec_mode_not_supp_in_speed = false;
-	u8 no_fec_policy = BIT(MLX5E_FEC_NOFEC);
 	u32 out[MLX5_ST_SZ_DW(pplm_reg)] = {};
 	u32 in[MLX5_ST_SZ_DW(pplm_reg)] = {};
 	int sz = MLX5_ST_SZ_BYTES(pplm_reg);
-	u32 current_fec_speed;
+	u8 fec_policy_auto = 0;
 	u8 fec_caps = 0;
 	int err;
 	int i;
@@ -415,23 +415,19 @@ int mlx5e_set_fec_mode(struct mlx5_core_dev *dev, u8 fec_policy)
 	if (err)
 		return err;
 
-	err = mlx5e_port_linkspeed(dev, &current_fec_speed);
-	if (err)
-		return err;
+	MLX5_SET(pplm_reg, out, local_port, 1);
 
-	memset(in, 0, sz);
-	MLX5_SET(pplm_reg, in, local_port, 1);
-	for (i = 0; i < MLX5E_FEC_SUPPORTED_SPEEDS && !!fec_policy; i++) {
+	for (i = 0; i < MLX5E_FEC_SUPPORTED_SPEEDS; i++) {
 		mlx5e_get_fec_cap_field(out, &fec_caps, fec_supported_speeds[i]);
-		/* policy supported for link speed */
-		if (!!(fec_caps & fec_policy)) {
-			mlx5e_fec_admin_field(in, &fec_policy, 1,
+		/* policy supported for link speed, or policy is auto */
+		if (fec_caps & fec_policy || fec_policy == fec_policy_auto) {
+			mlx5e_fec_admin_field(out, &fec_policy, 1,
 					      fec_supported_speeds[i]);
 		} else {
-			if (fec_supported_speeds[i] == current_fec_speed)
-				return -EOPNOTSUPP;
-			mlx5e_fec_admin_field(in, &no_fec_policy, 1,
-					      fec_supported_speeds[i]);
+			/* turn off FEC if supported. Else, leave it the same */
+			if (fec_caps & fec_policy_nofec)
+				mlx5e_fec_admin_field(out, &fec_policy_nofec, 1,
+						      fec_supported_speeds[i]);
 			fec_mode_not_supp_in_speed = true;
 		}
 	}
@@ -441,5 +437,5 @@ int mlx5e_set_fec_mode(struct mlx5_core_dev *dev, u8 fec_policy)
 			      "FEC policy 0x%x is not supported for some speeds",
 			      fec_policy);
 
-	return mlx5_core_access_reg(dev, in, sz, out, sz, MLX5_REG_PPLM, 0, 1);
+	return mlx5_core_access_reg(dev, out, sz, out, sz, MLX5_REG_PPLM, 0, 1);
 }