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Date:   Wed, 20 Feb 2019 11:14:41 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Artur Rojek <contact@...ur-rojek.eu>
Cc:     Sebastian Reichel <sre@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>, linux-pm@...r.kernel.org,
        linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, Paul Cercueil <paul@...pouillou.net>
Subject: Re: [PATCH 5/7] power: supply: add Ingenic JZ47xx battery driver.

On Sun, 17 Feb 2019 15:29:14 +0100
Artur Rojek <contact@...ur-rojek.eu> wrote:

> Add a driver for battery present on Ingenic JZ47xx SoCs.
> 
> Signed-off-by: Artur Rojek <contact@...ur-rojek.eu>
A few things inline.

thanks,

Jonathan

> ---
>  drivers/power/supply/Kconfig           |  11 ++
>  drivers/power/supply/Makefile          |   1 +
>  drivers/power/supply/ingenic-battery.c | 182 +++++++++++++++++++++++++
>  3 files changed, 194 insertions(+)
>  create mode 100644 drivers/power/supply/ingenic-battery.c
> 
> diff --git a/drivers/power/supply/Kconfig b/drivers/power/supply/Kconfig
> index e901b9879e7e..9bfb1637ec28 100644
> --- a/drivers/power/supply/Kconfig
> +++ b/drivers/power/supply/Kconfig
> @@ -169,6 +169,17 @@ config BATTERY_COLLIE
>  	  Say Y to enable support for the battery on the Sharp Zaurus
>  	  SL-5500 (collie) models.
>  
> +config BATTERY_INGENIC
> +	tristate "Ingenic JZ47xx SoCs battery driver"
> +	depends on MIPS || COMPILE_TEST
> +	depends on INGENIC_ADC
> +	help
> +	  Choose this option if you want to monitor battery status on
> +	  Ingenic JZ47xx SoC based devices.
> +
> +	  This driver can also be built as a module. If so, the module will be
> +	  called ingenic-battery.
> +
>  config BATTERY_IPAQ_MICRO
>  	tristate "iPAQ Atmel Micro ASIC battery driver"
>  	depends on MFD_IPAQ_MICRO
> diff --git a/drivers/power/supply/Makefile b/drivers/power/supply/Makefile
> index b731c2a9b695..9e2c481d0187 100644
> --- a/drivers/power/supply/Makefile
> +++ b/drivers/power/supply/Makefile
> @@ -34,6 +34,7 @@ obj-$(CONFIG_BATTERY_PMU)	+= pmu_battery.o
>  obj-$(CONFIG_BATTERY_OLPC)	+= olpc_battery.o
>  obj-$(CONFIG_BATTERY_TOSA)	+= tosa_battery.o
>  obj-$(CONFIG_BATTERY_COLLIE)	+= collie_battery.o
> +obj-$(CONFIG_BATTERY_INGENIC)	+= ingenic-battery.o
>  obj-$(CONFIG_BATTERY_IPAQ_MICRO) += ipaq_micro_battery.o
>  obj-$(CONFIG_BATTERY_WM97XX)	+= wm97xx_battery.o
>  obj-$(CONFIG_BATTERY_SBS)	+= sbs-battery.o
> diff --git a/drivers/power/supply/ingenic-battery.c b/drivers/power/supply/ingenic-battery.c
> new file mode 100644
> index 000000000000..4ee75c1ac241
> --- /dev/null
> +++ b/drivers/power/supply/ingenic-battery.c
> @@ -0,0 +1,182 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Battery driver for the Ingenic JZ47xx SoCs
> + * Copyright (c) 2019 Artur Rojek <contact@...ur-rojek.eu>
> + *
> + * based on drivers/power/supply/jz4740-battery.c

What is the relationship between this driver and the older one?

> + */
> +
> +#include <linux/iio/consumer.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/power_supply.h>
> +#include <linux/property.h>
> +
> +struct ingenic_battery {
> +	struct device *dev;
> +	struct iio_channel *channel;
> +	struct power_supply_desc desc;
> +	struct power_supply *battery;
> +	struct power_supply_battery_info info;
> +};
> +
> +static int ingenic_battery_get_property(struct power_supply *psy,
> +					enum power_supply_property psp,
> +					union power_supply_propval *val)
> +{
> +	struct ingenic_battery *bat = power_supply_get_drvdata(psy);
> +	struct power_supply_battery_info *info = &bat->info;
> +	int ret = 0;
> +
> +	switch (psp) {
> +	case POWER_SUPPLY_PROP_HEALTH:
> +		ret = iio_read_channel_processed(bat->channel, &val->intval);
> +		val->intval *= 1000;
> +		if (val->intval < info->voltage_min_design_uv)
> +			val->intval = POWER_SUPPLY_HEALTH_DEAD;
> +		else if (val->intval > info->voltage_max_design_uv)
> +			val->intval = POWER_SUPPLY_HEALTH_OVERVOLTAGE;
> +		else
> +			val->intval = POWER_SUPPLY_HEALTH_GOOD;
> +	break;
> +	case POWER_SUPPLY_PROP_VOLTAGE_NOW:
> +		ret = iio_read_channel_processed(bat->channel, &val->intval);
> +		val->intval *= 1000;
> +	break;
> +	case POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN:
> +		val->intval = info->voltage_min_design_uv;
> +	break;
> +	case POWER_SUPPLY_PROP_VOLTAGE_MAX_DESIGN:
> +		val->intval = info->voltage_max_design_uv;
> +	break;
> +	default:
> +		return -EINVAL;
> +	};
> +
Can't get here, so drop.

> +	return ret;
> +}
> +
> +/* Set the most appropriate IIO channel voltage reference scale
> + * based on the battery's max voltage.
> + */
> +static int ingenic_battery_set_scale(struct ingenic_battery *bat)
> +{
> +	const int *scale_raw;
> +	int scale_len, scale_type, best_idx = -1, best_mV, max_raw, i, ret;
> +	u64 max_mV;
> +
> +	ret = iio_read_max_channel_raw(bat->channel, &max_raw);
> +	if (ret) {
> +		dev_err(bat->dev, "Unable to read max raw channel value\n");
> +		return ret;
> +	}
> +
> +	ret = iio_read_avail_channel_attribute(bat->channel, &scale_raw,
> +					       &scale_type, &scale_len,
> +					       IIO_CHAN_INFO_SCALE);
> +	if (ret < 0) {
> +		dev_err(bat->dev, "Unable to read channel avail scale\n");
> +		return ret;
> +	}
This works under the constraints of knowing what ADC we are talking to, but
this isn't generic.  The relationship between scale and the range isn't always
direct.  i.e. there are devices where you sample the same range at a lower
scale to be able to read it faster (can be thought of as oversampling, or
just not running the last stages of a pipelined ADC).
Anyhow, doesn't matter here as I assume this is fine on this part.

> +	if (ret != IIO_AVAIL_LIST || scale_type != IIO_VAL_FRACTIONAL_LOG2)
> +		return -EINVAL;
> +
> +	max_mV = bat->info.voltage_max_design_uv / 1000;
> +
> +	for (i = 1; i < scale_len; i += 2) {
> +		u64 scale_mV = (max_raw * scale_raw[i - 1]) >> scale_raw[i];
Not keen on the offset in the index being backwards.

This would be clearer I think as

for (i = 0; i < scale_len; i+= 2) {
	u64 scale_mv = (max_raw * scale_raw[i]) >> scale_raw[i + 1];
	...
	best_idx = i;
}

> +
> +		if (scale_mV < max_mV)
> +			continue;
> +
> +		if (best_idx >= 0 && scale_mV > best_mV)
> +			continue;
> +
> +		best_mV = scale_mV;
> +		best_idx = i - 1;
> +	}
> +
> +	if (best_idx < 0) {
> +		dev_err(bat->dev, "Unable to find matching voltage scale\n");
> +		return -EINVAL;
> +	}
> +
> +	return iio_write_channel_attribute(bat->channel,
> +					   scale_raw[best_idx],
> +					   scale_raw[best_idx+1],

Spacing around that +.

> +					   IIO_CHAN_INFO_SCALE);
> +}
> +
> +static enum power_supply_property ingenic_battery_properties[] = {
> +	POWER_SUPPLY_PROP_HEALTH,
> +	POWER_SUPPLY_PROP_VOLTAGE_NOW,
> +	POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN,
> +	POWER_SUPPLY_PROP_VOLTAGE_MAX_DESIGN,
> +};
> +
> +static int ingenic_battery_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct ingenic_battery *bat;
> +	struct power_supply_config psy_cfg = {};
> +	struct power_supply_desc *desc;
> +	int ret;
> +
> +	bat = devm_kzalloc(dev, sizeof(*bat), GFP_KERNEL);
> +	if (!bat)
> +		return -ENOMEM;
> +
> +	bat->dev = dev;
> +	bat->channel = devm_iio_channel_get(dev, "battery");
> +	if (IS_ERR(bat->channel))
> +		return PTR_ERR(bat->channel);
> +
> +	desc = &bat->desc;
> +	desc->name = "jz-battery";
> +	desc->type = POWER_SUPPLY_TYPE_BATTERY;
> +	desc->properties = ingenic_battery_properties;
> +	desc->num_properties = ARRAY_SIZE(ingenic_battery_properties);
> +	desc->get_property = ingenic_battery_get_property;
> +	psy_cfg.drv_data = bat;
> +	psy_cfg.of_node = dev->of_node;
> +
> +	bat->battery = devm_power_supply_register(dev, desc, &psy_cfg);
> +	if (IS_ERR(bat->battery)) {
> +		dev_err(dev, "Unable to register battery\n");
> +		return PTR_ERR(bat->battery);
> +	}
> +
> +	ret = power_supply_get_battery_info(bat->battery, &bat->info);
> +	if (ret) {
> +		dev_err(dev, "Unable to get battery info: %d\n", ret);
> +		return ret;
> +	}
> +	if (bat->info.voltage_min_design_uv < 0) {
> +		dev_err(dev, "Unable to get voltage min design\n");
> +		return bat->info.voltage_min_design_uv;
> +	}
> +	if (bat->info.voltage_max_design_uv < 0) {
> +		dev_err(dev, "Unable to get voltage max design\n");
> +		return bat->info.voltage_max_design_uv;
> +	}
> +
> +	return ingenic_battery_set_scale(bat);
> +}
> +
> +#ifdef CONFIG_OF
> +static const struct of_device_id ingenic_battery_of_match[] = {
> +	{ .compatible = "ingenic,jz4740-battery", },
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(of, ingenic_battery_of_match);
> +#endif
> +
> +static struct platform_driver ingenic_battery_driver = {
> +	.driver = {
> +		.name = "ingenic-battery",
> +		.of_match_table = of_match_ptr(ingenic_battery_of_match),
> +	},
> +	.probe = ingenic_battery_probe,
> +};
> +module_platform_driver(ingenic_battery_driver);

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