linux-kernel - RE: [PATCH v2 1/2] power: supply: add input voltage limit property.

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Date:   Thu, 22 Nov 2018 16:54:43 +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>,
        Adam Thomson <Adam.Thomson.Opensource@...semi.com>,
        "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 v2 1/2] power: supply: add input voltage limit property.

On 22 November 2018 10:11, 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.
> 
> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@...labora.com>
> Reviewed-by: Guenter Roeck <groeck@...omium.org>

Acked-by: Adam Thomson <Adam.Thomson.Opensource@...semi.com>

> ---
> 
> Changes in v2:
> - Document the new property in ABI/testing/sysfs-class-power.
> - Add the Reviewed-by Guenter Roeck tag.
> 
>  Documentation/ABI/testing/sysfs-class-power | 11 +++++++++++
> Documentation/power/power_supply_class.txt  |  2 ++
>  drivers/power/supply/power_supply_sysfs.c   |  1 +
>  include/linux/power_supply.h                |  1 +
>  4 files changed, 15 insertions(+)
> 
> diff --git a/Documentation/ABI/testing/sysfs-class-power
> b/Documentation/ABI/testing/sysfs-class-power
> index 5e23e22dce1b..4fb24b0a28df 100644
> --- a/Documentation/ABI/testing/sysfs-class-power
> +++ b/Documentation/ABI/testing/sysfs-class-power
> @@ -335,6 +335,17 @@ Description:
>  		Access: Read, Write
>  		Valid values: Represented in microamps
> 
> +What:		/sys/class/power_supply/<supply_name>/input_voltage_limit
> +Date:		Nov 2018
> +Contact:	linux-pm@...r.kernel.org
> +Description:
> +		Details the incoming VBUS voltage limit currently set in the
> +		supply. Normally this is configured based on the type of
> +		connection made.
> +
> +		Access: Read, Write
> +		Valid values: Represented in microvolts
> +
>  What:		/sys/class/power_supply/<supply_name>/online,
>  Date:		May 2007
>  Contact:	linux-pm@...r.kernel.org
> 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