linux-kernel - RE: [PATCH 1/2] power: supply: add input voltage limit property.

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Date:   Wed, 21 Nov 2018 22:11:47 +0000
From:   Adam Thomson <Adam.Thomson.Opensource@...semi.com>
To:     Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "sre@...nel.org" <sre@...nel.org>
CC:     Sameer Nanda <snanda@...omium.org>,
        "gwendal@...omium.org" <gwendal@...omium.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "groeck@...omium.org" <groeck@...omium.org>,
        "kernel@...labora.com" <kernel@...labora.com>,
        "bleung@...omium.org" <bleung@...omium.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>
Subject: RE: [PATCH 1/2] power: supply: add input voltage limit property.

On 21 November 2018 15:35, Enric Balletbo i Serra wrote:

> We have a problem with USBPD chargers which under certain conditions 
> can result in system overheating if the voltage provided by the USBPD 
> port is too high. While the preferred means to control this would be 
> through devicetree or ACPI settings, this is not always possible, and 
> we need to have a means to set a voltage limit.
> 
> This patch exposes a new property, similar to input current limit, to 
> re-configure the maximum voltage from the external supply at runtime 
> based on system-level knowledge or user input.

I think we should be adding new documentation to the following file for any property changes:

Documentation/ABI/testing/sysfs-class-power

Sebastian can maybe comment further though. 
 
> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@...labora.com>
> ---
> 
>  Documentation/power/power_supply_class.txt | 2 ++ 
> drivers/power/supply/power_supply_sysfs.c  | 1 +
>  include/linux/power_supply.h               | 1 +
>  3 files changed, 4 insertions(+)
> 
> diff --git a/Documentation/power/power_supply_class.txt
> b/Documentation/power/power_supply_class.txt
> index 300d37896e51..7b4be615b4f8 100644
> --- a/Documentation/power/power_supply_class.txt
> +++ b/Documentation/power/power_supply_class.txt
> @@ -137,6 +137,8 @@ power supply object.
> 
>  INPUT_CURRENT_LIMIT - input current limit programmed by charger. 
> Indicates the current drawn from a charging source.
> +INPUT_VOLTAGE_LIMIT - input voltage limit programmed by charger.
> +Indicates the voltage limit from a charging source.
> 
>  CHARGE_CONTROL_LIMIT - current charge control limit setting 
> CHARGE_CONTROL_LIMIT_MAX - maximum charge control limit setting diff 
> --git a/drivers/power/supply/power_supply_sysfs.c
> b/drivers/power/supply/power_supply_sysfs.c
> index dce24f596160..5848742ebb59 100644
> --- a/drivers/power/supply/power_supply_sysfs.c
> +++ b/drivers/power/supply/power_supply_sysfs.c
> @@ -275,6 +275,7 @@ static struct device_attribute power_supply_attrs[] = {
>  	POWER_SUPPLY_ATTR(charge_control_limit),
>  	POWER_SUPPLY_ATTR(charge_control_limit_max),
>  	POWER_SUPPLY_ATTR(input_current_limit),
> +	POWER_SUPPLY_ATTR(input_voltage_limit),
>  	POWER_SUPPLY_ATTR(energy_full_design),
>  	POWER_SUPPLY_ATTR(energy_empty_design),
>  	POWER_SUPPLY_ATTR(energy_full),
> diff --git a/include/linux/power_supply.h 
> b/include/linux/power_supply.h index f80769175c56..608ba88e32ee 100644
> --- a/include/linux/power_supply.h
> +++ b/include/linux/power_supply.h
> @@ -122,6 +122,7 @@ enum power_supply_property {
>  	POWER_SUPPLY_PROP_CHARGE_CONTROL_LIMIT,
>  	POWER_SUPPLY_PROP_CHARGE_CONTROL_LIMIT_MAX,
>  	POWER_SUPPLY_PROP_INPUT_CURRENT_LIMIT,
> +	POWER_SUPPLY_PROP_INPUT_VOLTAGE_LIMIT,
>  	POWER_SUPPLY_PROP_ENERGY_FULL_DESIGN,
>  	POWER_SUPPLY_PROP_ENERGY_EMPTY_DESIGN,
>  	POWER_SUPPLY_PROP_ENERGY_FULL,
> --
> 2.19.1