linux-kernel - Re: [PATCH v2 2/2] power: charger-manager: Avoid recursive thermal get

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Date:	Mon, 13 Oct 2014 06:01:18 +0000 (GMT)
From:	MyungJoo Ham <myungjoo.ham@...sung.com>
To:	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Sebastian Reichel <sre@...nel.org>,
	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Anton Vorontsov <anton@...msg.org>,
	이종화 <jonghwa3.lee@...sung.com>,
	최찬우 <cw00.choi@...sung.com>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:	박경민 <kyungmin.park@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [PATCH v2 2/2] power: charger-manager: Avoid recursive thermal
 get_temp call

>   
>  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@...sung.com>

Do we really need to add another variable in the psy struct?
In the previous thread, I thought that wasn't needed, though.


Cheers,
MyungJoo

> 
> ---
> 
> Changes since v1:
> 1. New patch (new idea).
> ---
>  drivers/power/power_supply_core.c | 3 +++
>  include/linux/power_supply.h      | 6 ++++++
>  2 files changed, 9 insertions(+)
> 
> diff --git a/drivers/power/power_supply_core.c b/drivers/power/power_supply_core.c
> index 6cb7fe5c022d..694e8cddd5c1 100644
> --- a/drivers/power/power_supply_core.c
> +++ b/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) {
> diff --git a/include/linux/power_supply.h b/include/linux/power_supply.h
> index 3ed049673022..096dbced02ac 100644
> --- a/include/linux/power_supply.h
> +++ b/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;
>  
> -- 
> 1.9.1
>