power_supply: Add no_thermal property to prevent recursive get_temp calls

Add a 'no_thermal' property to the power supply class. If true then
thermal zone won't be created for this power supply in
power_supply_register().

Power supply drivers may want to set it if they support
POWER_SUPPLY_PROP_TEMP and they are forwarding this get property call to
other thermal zone.

If they won't set it lockdep may report false positive deadlock for
thermal zone's mutex because of nested calls to thermal_zone_get_temp().
First is the call to thermal_zone_get_temp() of the driver's thermal
zone. Thermal core gets POWER_SUPPLY_PROP_TEMP property from this
driver. The driver then calls other thermal zone thermal_zone_get_temp()
and returns result.

Example of such driver is charger manager.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>

drivers/power/power_supply_core.c

@@ -417,6 +417,9 @@ static int psy_register_thermal(struct power_supply *psy)
 {
 	int i;
 
+	if (psy->no_thermal)
+		return 0;
+
 	/* Register battery zone device psy reports temperature */
 	for (i = 0; i < psy->num_properties; i++) {
 		if (psy->properties[i] == POWER_SUPPLY_PROP_TEMP) {

include/linux/power_supply.h

@@ -200,6 +200,12 @@ struct power_supply {
 	void (*external_power_changed)(struct power_supply *psy);
 	void (*set_charged)(struct power_supply *psy);
 
+	/*
+	 * Set if thermal zone should not be created for this power supply.
+	 * For example for virtual supplies forwarding calls to actual
+	 * sensors or other supplies.
+	 */
+	bool no_thermal;
 	/* For APM emulation, think legacy userspace. */
 	int use_for_apm;