usb: typec: tcpm: add get max power support

Traverse fixed pdos to calculate the maximum power that the charger
can provide, and it can be get by POWER_SUPPLY_PROP_INPUT_POWER_LIMIT
property.

Signed-off-by: Frank Wang <frank.wang@rock-chips.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20230616075241.27690-2-frank.wang@rock-chips.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Frank Wang

drivers/usb/typec/tcpm/tcpm.c

@@ -6340,6 +6340,27 @@ static int tcpm_psy_get_current_now(struct tcpm_port *port,
 	return 0;
 }
 
+static int tcpm_psy_get_input_power_limit(struct tcpm_port *port,
+					  union power_supply_propval *val)
+{
+	unsigned int src_mv, src_ma, max_src_uw = 0;
+	unsigned int i, tmp;
+
+	for (i = 0; i < port->nr_source_caps; i++) {
+		u32 pdo = port->source_caps[i];
+
+		if (pdo_type(pdo) == PDO_TYPE_FIXED) {
+			src_mv = pdo_fixed_voltage(pdo);
+			src_ma = pdo_max_current(pdo);
+			tmp = src_mv * src_ma;
+			max_src_uw = tmp > max_src_uw ? tmp : max_src_uw;
+		}
+	}
+
+	val->intval = max_src_uw;
+	return 0;
+}
+
 static int tcpm_psy_get_prop(struct power_supply *psy,
 			     enum power_supply_property psp,
 			     union power_supply_propval *val)
@@ -6369,6 +6390,9 @@ static int tcpm_psy_get_prop(struct power_supply *psy,
 	case POWER_SUPPLY_PROP_CURRENT_NOW:
 		ret = tcpm_psy_get_current_now(port, val);
 		break;
+	case POWER_SUPPLY_PROP_INPUT_POWER_LIMIT:
+		tcpm_psy_get_input_power_limit(port, val);
+		break;
 	default:
 		ret = -EINVAL;
 		break;