Date:   Thu, 27 Jun 2019 20:36:42 +0200
From:   Sebastian Reichel <sre@...nel.org>
To:     Nick Crews <ncrews@...omium.org>
Cc:     enric.balletbo@...labora.com, bleung@...omium.org,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        dlaurie@...omium.org, lamzin@...gle.com, bartfab@...gle.com,
        derat@...gle.com, dtor@...gle.com, sjg@...omium.org,
        jchwong@...omium.org, tbroch@...omium.org
Subject: Re: [PATCH v9 1/2] power_supply: wilco_ec: Add charging config driver

Hi,

On Wed, May 08, 2019 at 02:38:25PM -0600, Nick Crews wrote:
> Add a driver to control the charging algorithm used on Wilco
> devices. See Documentation/ABI/testing/sysfs-class-power-wilco
> for the userspace interface and other info.
> 
> Signed-off-by: Nick Crews <ncrews@...omium.org>
> Reviewed-by: Enric Balletbo i Serra <enric.balletbo@...labora.com>

Thanks, queued.

-- Sebastian

> ---
> v9 changes:
> -Split up adding the driver and adding the device.
> v8 changes:
> -Several documentation and comment fixups.
> v6 changes:
> -Remove CHARGE_MODE_ILLEGAL from enum charge_mode. It's not a
>  public type, and error checking could be performed in other ways.
> -Split up the commit so properties are added in a first commit
> -Move CONFIG_CHARGER_WILCO to the power/supply Kconfig
> -Use PTR_ERR_OR_ZERO() macro in probe()
> v5 changes:
> -Remove OP_SYNC, it has no immediate use case.
> -Merge properties.h into wilco-ec.h
> -Remove enum get_set_sync_op from the public interface,
>  since without OP_SYNC they are irrelevant.
> -Fix Kconfigs and Makefiles so they actually work
>  with the v4 changes
> -Tweak some formatting, spacing, and comments
> -Fix validation of charge_type so illegal values
>  can't be set. Before negative error codes were
>  accidentally getting casted to positive numbers
> -Remove more unneeded parentheses.
> v4 changes:
> -Use put_unaligned_le32() to store PID in request.
> -Move implementation from
>  drivers/platform/chrome/wilco_ec/charge_config.c to
>  drivers/power/supply/wilco_charger.c
> -Move drivers/platform/chrome/wilco_ec/properties.h to
>  include/linux/platform_data/wilco-ec-properties.h
> -Remove parentheses in switch statement in psp_val_to_charge_mode()
> -Check for any negatvie return code from psp_val_to_charge_mode()
>  instead of just -EINVAL so its less brittle
> -Tweak comments in wilco-ec-properties.h
> v3 changes:
> -Add this changelog
> -Fix commit message tags
> v2 changes:
> -Update Documentation to say KernelVersion 5.2
> -Update Documentation to explain Trickle mode better.
> -rename things from using *PCC* to *CHARGE*
> -Split up conversions between POWER_SUPPLY_PROP_CHARGE_TYPE values
> and Wilco EC codes
> -Use devm_ flavor of power_supply_register(), which simplifies things
> -Add extra error checking on property messages received from the EC
> -Fix bug in memcpy() calls in properties.c
> -Refactor fill_property_id()
> -Add valid input checks to charge_type
> -Properly convert charge_type when get()ting
> 
>  .../ABI/testing/sysfs-class-power-wilco       |  30 +++
>  drivers/power/supply/Kconfig                  |   9 +
>  drivers/power/supply/Makefile                 |   1 +
>  drivers/power/supply/wilco-charger.c          | 187 ++++++++++++++++++
>  4 files changed, 227 insertions(+)
>  create mode 100644 Documentation/ABI/testing/sysfs-class-power-wilco
>  create mode 100644 drivers/power/supply/wilco-charger.c
> 
> diff --git a/Documentation/ABI/testing/sysfs-class-power-wilco b/Documentation/ABI/testing/sysfs-class-power-wilco
> new file mode 100644
> index 000000000000..da1d6ffe5e3c
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-class-power-wilco
> @@ -0,0 +1,30 @@
> +What:		/sys/class/power_supply/wilco-charger/charge_type
> +Date:		April 2019
> +KernelVersion:	5.2
> +Description:
> +		What charging algorithm to use:
> +
> +		Standard: Fully charges battery at a standard rate.
> +		Adaptive: Battery settings adaptively optimized based on
> +			typical battery usage pattern.
> +		Fast: Battery charges over a shorter period.
> +		Trickle: Extends battery lifespan, intended for users who
> +			primarily use their Chromebook while connected to AC.
> +		Custom: A low and high threshold percentage is specified.
> +			Charging begins when level drops below
> +			charge_control_start_threshold, and ceases when
> +			level is above charge_control_end_threshold.
> +
> +What:		/sys/class/power_supply/wilco-charger/charge_control_start_threshold
> +Date:		April 2019
> +KernelVersion:	5.2
> +Description:
> +		Used when charge_type="Custom", as described above. Measured in
> +		percentages. The valid range is [50, 95].
> +
> +What:		/sys/class/power_supply/wilco-charger/charge_control_end_threshold
> +Date:		April 2019
> +KernelVersion:	5.2
> +Description:
> +		Used when charge_type="Custom", as described above. Measured in
> +		percentages. The valid range is [55, 100].
> diff --git a/drivers/power/supply/Kconfig b/drivers/power/supply/Kconfig
> index e901b9879e7e..0c67eff871c8 100644
> --- a/drivers/power/supply/Kconfig
> +++ b/drivers/power/supply/Kconfig
> @@ -660,4 +660,13 @@ config FUEL_GAUGE_SC27XX
>  	 Say Y here to enable support for fuel gauge with SC27XX
>  	 PMIC chips.
>  
> +config CHARGER_WILCO
> +	tristate "Wilco EC based charger for ChromeOS"
> +	depends on WILCO_EC
> +	help
> +	  Say Y here to enable control of the charging routines performed
> +	  by the Embedded Controller on the Chromebook named Wilco. Further
> +	  information can be found in
> +	  Documentation/ABI/testing/sysfs-class-power-wilco
> +
>  endif # POWER_SUPPLY
> diff --git a/drivers/power/supply/Makefile b/drivers/power/supply/Makefile
> index b731c2a9b695..2b603a142701 100644
> --- a/drivers/power/supply/Makefile
> +++ b/drivers/power/supply/Makefile
> @@ -87,3 +87,4 @@ obj-$(CONFIG_AXP288_CHARGER)	+= axp288_charger.o
>  obj-$(CONFIG_CHARGER_CROS_USBPD)	+= cros_usbpd-charger.o
>  obj-$(CONFIG_CHARGER_SC2731)	+= sc2731_charger.o
>  obj-$(CONFIG_FUEL_GAUGE_SC27XX)	+= sc27xx_fuel_gauge.o
> +obj-$(CONFIG_CHARGER_WILCO)	+= wilco-charger.o
> diff --git a/drivers/power/supply/wilco-charger.c b/drivers/power/supply/wilco-charger.c
> new file mode 100644
> index 000000000000..b3c6d7cdd731
> --- /dev/null
> +++ b/drivers/power/supply/wilco-charger.c
> @@ -0,0 +1,187 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Charging control driver for the Wilco EC
> + *
> + * Copyright 2019 Google LLC
> + *
> + * See Documentation/ABI/testing/sysfs-class-power and
> + * Documentation/ABI/testing/sysfs-class-power-wilco for userspace interface
> + * and other info.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/platform_data/wilco-ec.h>
> +#include <linux/power_supply.h>
> +
> +#define DRV_NAME "wilco-charger"
> +
> +/* Property IDs and related EC constants */
> +#define PID_CHARGE_MODE		0x0710
> +#define PID_CHARGE_LOWER_LIMIT	0x0711
> +#define PID_CHARGE_UPPER_LIMIT	0x0712
> +
> +enum charge_mode {
> +	CHARGE_MODE_STD = 1,	/* Used for Standard */
> +	CHARGE_MODE_EXP = 2,	/* Express Charge, used for Fast */
> +	CHARGE_MODE_AC = 3,	/* Mostly AC use, used for Trickle */
> +	CHARGE_MODE_AUTO = 4,	/* Used for Adaptive */
> +	CHARGE_MODE_CUSTOM = 5,	/* Used for Custom */
> +};
> +
> +#define CHARGE_LOWER_LIMIT_MIN	50
> +#define CHARGE_LOWER_LIMIT_MAX	95
> +#define CHARGE_UPPER_LIMIT_MIN	55
> +#define CHARGE_UPPER_LIMIT_MAX	100
> +
> +/* Convert from POWER_SUPPLY_PROP_CHARGE_TYPE value to the EC's charge mode */
> +static int psp_val_to_charge_mode(int psp_val)
> +{
> +	switch (psp_val) {
> +	case POWER_SUPPLY_CHARGE_TYPE_TRICKLE:
> +		return CHARGE_MODE_AC;
> +	case POWER_SUPPLY_CHARGE_TYPE_FAST:
> +		return CHARGE_MODE_EXP;
> +	case POWER_SUPPLY_CHARGE_TYPE_STANDARD:
> +		return CHARGE_MODE_STD;
> +	case POWER_SUPPLY_CHARGE_TYPE_ADAPTIVE:
> +		return CHARGE_MODE_AUTO;
> +	case POWER_SUPPLY_CHARGE_TYPE_CUSTOM:
> +		return CHARGE_MODE_CUSTOM;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +/* Convert from EC's charge mode to POWER_SUPPLY_PROP_CHARGE_TYPE value */
> +static int charge_mode_to_psp_val(enum charge_mode mode)
> +{
> +	switch (mode) {
> +	case CHARGE_MODE_AC:
> +		return POWER_SUPPLY_CHARGE_TYPE_TRICKLE;
> +	case CHARGE_MODE_EXP:
> +		return POWER_SUPPLY_CHARGE_TYPE_FAST;
> +	case CHARGE_MODE_STD:
> +		return POWER_SUPPLY_CHARGE_TYPE_STANDARD;
> +	case CHARGE_MODE_AUTO:
> +		return POWER_SUPPLY_CHARGE_TYPE_ADAPTIVE;
> +	case CHARGE_MODE_CUSTOM:
> +		return POWER_SUPPLY_CHARGE_TYPE_CUSTOM;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static enum power_supply_property wilco_charge_props[] = {
> +	POWER_SUPPLY_PROP_CHARGE_TYPE,
> +	POWER_SUPPLY_PROP_CHARGE_CONTROL_START_THRESHOLD,
> +	POWER_SUPPLY_PROP_CHARGE_CONTROL_END_THRESHOLD,
> +};
> +
> +static int wilco_charge_get_property(struct power_supply *psy,
> +				     enum power_supply_property psp,
> +				     union power_supply_propval *val)
> +{
> +	struct wilco_ec_device *ec = power_supply_get_drvdata(psy);
> +	u32 property_id;
> +	int ret;
> +	u8 raw;
> +
> +	switch (psp) {
> +	case POWER_SUPPLY_PROP_CHARGE_TYPE:
> +		property_id = PID_CHARGE_MODE;
> +		break;
> +	case POWER_SUPPLY_PROP_CHARGE_CONTROL_START_THRESHOLD:
> +		property_id = PID_CHARGE_LOWER_LIMIT;
> +		break;
> +	case POWER_SUPPLY_PROP_CHARGE_CONTROL_END_THRESHOLD:
> +		property_id = PID_CHARGE_UPPER_LIMIT;
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	ret = wilco_ec_get_byte_property(ec, property_id, &raw);
> +	if (ret < 0)
> +		return ret;
> +	if (property_id == PID_CHARGE_MODE) {
> +		ret = charge_mode_to_psp_val(raw);
> +		if (ret < 0)
> +			return -EBADMSG;
> +		raw = ret;
> +	}
> +	val->intval = raw;
> +
> +	return 0;
> +}
> +
> +static int wilco_charge_set_property(struct power_supply *psy,
> +				     enum power_supply_property psp,
> +				     const union power_supply_propval *val)
> +{
> +	struct wilco_ec_device *ec = power_supply_get_drvdata(psy);
> +	int mode;
> +
> +	switch (psp) {
> +	case POWER_SUPPLY_PROP_CHARGE_TYPE:
> +		mode = psp_val_to_charge_mode(val->intval);
> +		if (mode < 0)
> +			return -EINVAL;
> +		return wilco_ec_set_byte_property(ec, PID_CHARGE_MODE, mode);
> +	case POWER_SUPPLY_PROP_CHARGE_CONTROL_START_THRESHOLD:
> +		if (val->intval < CHARGE_LOWER_LIMIT_MIN ||
> +		    val->intval > CHARGE_LOWER_LIMIT_MAX)
> +			return -EINVAL;
> +		return wilco_ec_set_byte_property(ec, PID_CHARGE_LOWER_LIMIT,
> +						  val->intval);
> +	case POWER_SUPPLY_PROP_CHARGE_CONTROL_END_THRESHOLD:
> +		if (val->intval < CHARGE_UPPER_LIMIT_MIN ||
> +		    val->intval > CHARGE_UPPER_LIMIT_MAX)
> +			return -EINVAL;
> +		return wilco_ec_set_byte_property(ec, PID_CHARGE_UPPER_LIMIT,
> +						  val->intval);
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static int wilco_charge_property_is_writeable(struct power_supply *psy,
> +					      enum power_supply_property psp)
> +{
> +	return 1;
> +}
> +
> +static const struct power_supply_desc wilco_ps_desc = {
> +	.properties		= wilco_charge_props,
> +	.num_properties		= ARRAY_SIZE(wilco_charge_props),
> +	.get_property		= wilco_charge_get_property,
> +	.set_property		= wilco_charge_set_property,
> +	.property_is_writeable	= wilco_charge_property_is_writeable,
> +	.name			= DRV_NAME,
> +	.type			= POWER_SUPPLY_TYPE_MAINS,
> +};
> +
> +static int wilco_charge_probe(struct platform_device *pdev)
> +{
> +	struct wilco_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
> +	struct power_supply_config psy_cfg = {};
> +	struct power_supply *psy;
> +
> +	psy_cfg.drv_data = ec;
> +	psy = devm_power_supply_register(&pdev->dev, &wilco_ps_desc, &psy_cfg);
> +
> +	return PTR_ERR_OR_ZERO(psy);
> +}
> +
> +static struct platform_driver wilco_charge_driver = {
> +	.probe	= wilco_charge_probe,
> +	.driver = {
> +		.name = DRV_NAME,
> +	}
> +};
> +module_platform_driver(wilco_charge_driver);
> +
> +MODULE_ALIAS("platform:" DRV_NAME);
> +MODULE_AUTHOR("Nick Crews <ncrews@...omium.org>");
> +MODULE_LICENSE("GPL v2");
> +MODULE_DESCRIPTION("Wilco EC charge control driver");
> -- 
> 2.20.1
> 

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