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Date:	Tue, 07 Oct 2014 11:20:48 +0900
From:	jonghwa3.lee@...sung.com
To:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
Cc:	Sebastian Reichel <sre@...nel.org>,
	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Myungjoo Ham <myungjoo.ham@...sung.com>,
	Anton Vorontsov <anton@...msg.org>,
	Chanwoo Choi <cw00.choi@...sung.com>, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] power: charger-manager: Avoid recursive thermal get_temp
 call

Hi,
On 2014년 10월 07일 01:00, Krzysztof Kozlowski wrote:

> The charger manager supports POWER_SUPPLY_PROP_TEMP property and acts
> as a thermal zone if any of these conditions match:
> 1. Fuel gauge used by charger manager supports POWER_SUPPLY_PROP_TEMP.
> 2. 'cm-thermal-zone' property is present in DTS (then it will supersede
>    the fuel gauge temperature property).
> 
> However in case 1 (fuel gauge reports temperature and 'cm-thermal-zone'
> is not set) the charger manager forwards its get_temp calls to fuel
> gauge thermal zone.
> 
> This leads to reporting by lockdep a false positive deadlock for thermal
> zone's mutex because of nested calls to thermal_zone_get_temp(). This is
> false positive because these are different mutexes: one for charger
> manager thermal zone and second for fuel gauge thermal zone.
> 


Yes, this happens because power_supply_subsystem automatically creates
thermal_zone when POWER_SUPPLY_PROP_TEMP is available at the time of
power_supply registering. And as you point out, it makes duplicate thermal_zone
when some power_supply references other power_supply's. I hope it would become
to be a selectable option or change the manner of charger-manager itself (if the
charger-manager is only one who references other power_supply's temperature
sensing ability).

Anyway, the code looks fine to me.

Acked-by : Jonghwa Lee <jonghwa3.lee@...sung.com>

Thanks,
Jonghwa.

> Get rid of false lockdep alert and recursive call by accessing fuel gauge
> temperature through power supply property instead of thermal zone API.
> 

> Signed-off-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>
> ---
>  drivers/power/charger-manager.c       | 21 +++++++++++----------
>  include/linux/power/charger-manager.h |  2 --
>  2 files changed, 11 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/power/charger-manager.c b/drivers/power/charger-manager.c
> index c1ed3c99c059..871fb91429c8 100644
> --- a/drivers/power/charger-manager.c
> +++ b/drivers/power/charger-manager.c
> @@ -559,16 +559,18 @@ static int cm_get_battery_temperature(struct charger_manager *cm,
>  	if (!cm->desc->measure_battery_temp)
>  		return -ENODEV;
>  
> -#ifdef CONFIG_THERMAL
> -	ret = thermal_zone_get_temp(cm->tzd_batt, (unsigned long *)temp);
> -	if (!ret)
> -		/* Calibrate temperature unit */
> -		*temp /= 100;
> -#else
> -	ret = cm->fuel_gauge->get_property(cm->fuel_gauge,
> +	if (IS_ENABLED(CONFIG_THERMAL) && cm->tzd_batt) {
> +		ret = thermal_zone_get_temp(cm->tzd_batt, (unsigned long *)temp);
> +		if (!ret)
> +			/* Calibrate temperature unit */
> +			*temp /= 100;
> +	} else {
> +		/* No external thermometer or no CONFIG_THERMAL */
> +		ret = cm->fuel_gauge->get_property(cm->fuel_gauge,
>  				POWER_SUPPLY_PROP_TEMP,
>  				(union power_supply_propval *)temp);
> -#endif
> +	}
> +
>  	return ret;
>  }
>  
> @@ -1501,9 +1503,8 @@ static int cm_init_thermal_data(struct charger_manager *cm)
>  		cm->charger_psy.num_properties++;
>  		cm->desc->measure_battery_temp = true;
>  	}
> -#ifdef CONFIG_THERMAL
> -	cm->tzd_batt = cm->fuel_gauge->tzd;
>  
> +#ifdef CONFIG_THERMAL
>  	if (ret && desc->thermal_zone) {
>  		cm->tzd_batt =
>  			thermal_zone_get_zone_by_name(desc->thermal_zone);
> diff --git a/include/linux/power/charger-manager.h b/include/linux/power/charger-manager.h
> index 07e7945a1ff2..743ed6d472c6 100644
> --- a/include/linux/power/charger-manager.h
> +++ b/include/linux/power/charger-manager.h
> @@ -256,9 +256,7 @@ struct charger_manager {
>  	struct power_supply *fuel_gauge;
>  	struct power_supply **charger_stat;
>  
> -#ifdef CONFIG_THERMAL
>  	struct thermal_zone_device *tzd_batt;
> -#endif
>  	bool charger_enabled;
>  
>  	unsigned long fullbatt_vchk_jiffies_at;


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