Re: [PATCH 2/2] power: supply: Add Spreadtrum SC27XX fuel gauge unit driver

[Sebastian Reichel]

Hi,

Looks mostly good. I have a couple of comments in addition to the
ones from the binding about using battery_info for the OCV ->
capacity mapping.

On Wed, Sep 12, 2018 at 03:29:39PM +0800, Baolin Wang wrote:
> This patch adds the Spreadtrum SC27XX serial PMICs fuel gauge support,
> which is used to calculate the battery capacity.
> 
> Original-by: Yuanjiang Yu <yuanjiang.yu@xxxxxxxxxx>
> Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxx>
> ---
>  drivers/power/supply/Kconfig             |    7 +
>  drivers/power/supply/Makefile            |    1 +
>  drivers/power/supply/sc27xx_fuel_gauge.c |  705 ++++++++++++++++++++++++++++++
>  3 files changed, 713 insertions(+)
>  create mode 100644 drivers/power/supply/sc27xx_fuel_gauge.c
> 
> diff --git a/drivers/power/supply/Kconfig b/drivers/power/supply/Kconfig
> index f27cf07..917f4b7 100644
> --- a/drivers/power/supply/Kconfig
> +++ b/drivers/power/supply/Kconfig
> @@ -652,4 +652,11 @@ config CHARGER_SC2731
>  	 Say Y here to enable support for battery charging with SC2731
>  	 PMIC chips.
>  
> +config FUEL_GAUGE_SC27XX
> +	tristate "Spreadtrum SC27XX fuel gauge driver"
> +	depends on MFD_SC27XX_PMIC || COMPILE_TEST
> +	help
> +	 Say Y here to enable support for fuel gauge with SC27XX
> +	 PMIC chips.
> +
>  endif # POWER_SUPPLY
> diff --git a/drivers/power/supply/Makefile b/drivers/power/supply/Makefile
> index 767105b..b731c2a 100644
> --- a/drivers/power/supply/Makefile
> +++ b/drivers/power/supply/Makefile
> @@ -86,3 +86,4 @@ obj-$(CONFIG_AXP288_FUEL_GAUGE) += axp288_fuel_gauge.o
>  obj-$(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
> diff --git a/drivers/power/supply/sc27xx_fuel_gauge.c b/drivers/power/supply/sc27xx_fuel_gauge.c
> new file mode 100644
> index 0000000..4df0f47
> --- /dev/null
> +++ b/drivers/power/supply/sc27xx_fuel_gauge.c
> @@ -0,0 +1,705 @@
> +// SPDX-License-Identifier: GPL-2.0
> +// Copyright (C) 2018 Spreadtrum Communications Inc.
> +
> +#include <linux/gpio/consumer.h>
> +#include <linux/iio/consumer.h>
> +#include <linux/interrupt.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/power_supply.h>
> +#include <linux/regmap.h>
> +
> +/* PMIC global control registers definition */
> +#define SC27XX_MODULE_EN0		0xc08
> +#define SC27XX_CLK_EN0			0xc18
> +#define SC27XX_FGU_EN			BIT(7)
> +#define SC27XX_FGU_RTC_EN		BIT(6)
> +
> +/* FGU registers definition */
> +#define SC27XX_FGU_START		0x0
> +#define SC27XX_FGU_CONFIG		0x4
> +#define SC27XX_FGU_ADC_CONFIG		0x8
> +#define SC27XX_FGU_STATUS		0xc
> +#define SC27XX_FGU_INT_EN		0x10
> +#define SC27XX_FGU_INT_CLR		0x14
> +#define SC27XX_FGU_INT_STS		0x1c
> +#define SC27XX_FGU_VOLTAGE		0x20
> +#define SC27XX_FGU_OCV			0x24
> +#define SC27XX_FGU_POCV			0x28
> +#define SC27XX_FGU_CURRENT		0x2c
> +#define SC27XX_FGU_CLBCNT_SETH		0x50
> +#define SC27XX_FGU_CLBCNT_SETL		0x54
> +#define SC27XX_FGU_CLBCNT_VALH		0x68
> +#define SC27XX_FGU_CLBCNT_VALL		0x6c
> +#define SC27XX_FGU_CLBCNT_QMAXL		0x74
> +
> +#define SC27XX_WRITE_SELCLB_EN		BIT(0)
> +#define SC27XX_FGU_CLBCNT_MASK		GENMASK(15, 0)
> +#define SC27XX_FGU_CLBCNT_SHIFT		16
> +
> +#define SC27XX_FGU_1000MV_ADC		686
> +#define SC27XX_FGU_1000MA_ADC		1372
> +#define SC27XX_FGU_CUR_BASIC_ADC	8192
> +#define SC27XX_FGU_SAMPLE_HZ		2
> +
> +struct sc27xx_fgu_capacity_table {
> +	int ocv;
> +	int capacity;
> +};
> +
> +/*
> + * struct sc27xx_fgu_data: describe the FGU device
> + * @regmap: regmap for register access
> + * @dev: platform device
> + * @battery: battery power supply
> + * @base: the base offset for the controller
> + * @lock: protect the structure
> + * @gpiod: GPIO for battery detection
> + * @channel: IIO channel to get battery temperature
> + * @inner_resist: the battery inner resistance in mOhm
> + * @total_cap: the total capacity of the battery in mAh
> + * @init_cap: the initial capacity of the battery in mAh
> + * @init_clbcnt: the initial coulomb counter
> + * @max_volt: the maximum constant input voltage in millivolt
> + * @table_len: the capacity table length
> + * @cap_table: capacity table with corresponding ocv
> + */
> +struct sc27xx_fgu_data {
> +	struct regmap *regmap;
> +	struct device *dev;
> +	struct power_supply *battery;
> +	u32 base;
> +	struct mutex lock;
> +	struct gpio_desc *gpiod;
> +	struct iio_channel *channel;
> +	bool bat_present;
> +	int inner_resist;
> +	int total_cap;
> +	int init_cap;
> +	int init_clbcnt;
> +	int max_volt;
> +	int table_len;
> +	struct sc27xx_fgu_capacity_table *cap_table;
> +};
> +
> +static const char * const sc27xx_charger_supply_name[] = {
> +	"sc2731_charger",
> +	"sc2720_charger",
> +	"sc2721_charger",
> +	"sc2723_charger",
> +};
> +
> +static int sc27xx_fgu_adc_to_current(int adc)
> +{
> +	return (adc * 1000) / SC27XX_FGU_1000MA_ADC;
> +}
> +
> +static int sc27xx_fgu_adc_to_voltage(int adc)
> +{
> +	return (adc * 1000) / SC27XX_FGU_1000MV_ADC;
> +}
> +
> +static int sc27xx_fgu_ocv_to_capacity(struct sc27xx_fgu_data *data, int ocv)
> +{
> +	struct sc27xx_fgu_capacity_table *tab = data->cap_table;
> +	int n = data->table_len;
> +	int i, cap, tmp;
> +
> +	/*
> +	 * Find the position in the table for current battery OCV value,
> +	 * then use these two points to calculate battery capacity
> +	 * according to the linear method.
> +	 */
> +	for (i = 0; i < n; i++)
> +		if (ocv > tab[i].ocv)
> +			break;
> +
> +	if (i > 0 && i < n) {
> +		tmp = (tab[i - 1].capacity - tab[i].capacity) *
> +			(ocv - tab[i].ocv) * 2;
> +		tmp /= tab[i - 1].ocv - tab[i].ocv;
> +		tmp = (tmp + 1) / 2;
> +		cap = tmp + tab[i].capacity;
> +	} else if (i == 0) {
> +		cap = tab[0].capacity;
> +	} else {
> +		cap = tab[n - 1].capacity;
> +	}
> +
> +	return cap;
> +}
> +
> +/*
> + * When system boots on, we can not read battery capacity from coulomb
> + * registers, since now the coulomb registers are invalid. So we should
> + * calculate the battery open circuit voltage, and get current battery
> + * capacity according to the capacity table.
> + */
> +static int sc27xx_fgu_get_boot_capacity(struct sc27xx_fgu_data *data, int *cap)
> +{
> +	int volt, cur, oci, ocv, ret;
> +
> +	/*
> +	 * After system booting on, the SC27XX_FGU_CLBCNT_QMAXL register saved
> +	 * the first sampled open circuit current.
> +	 */
> +	ret = regmap_read(data->regmap, data->base + SC27XX_FGU_CLBCNT_QMAXL,
> +			  &cur);
> +	if (ret)
> +		return ret;
> +
> +	cur <<= 1;
> +	oci = sc27xx_fgu_adc_to_current(cur - SC27XX_FGU_CUR_BASIC_ADC);
> +
> +	/*
> +	 * Should get the OCV from SC27XX_FGU_POCV register at the system
> +	 * beginning. It is ADC values reading from registers which need to
> +	 * convert the corresponding voltage.
> +	 */
> +	ret = regmap_read(data->regmap, data->base + SC27XX_FGU_POCV, &volt);
> +	if (ret)
> +		return ret;
> +
> +	volt = sc27xx_fgu_adc_to_voltage(volt);
> +	ocv = volt - (oci * data->inner_resist) / 1000;
> +
> +	/*
> +	 * Parse the capacity table to look up the correct capacity percent
> +	 * according to current battery's corresponding OCV values.
> +	 */
> +	*cap = sc27xx_fgu_ocv_to_capacity(data, ocv);
> +
> +	return 0;
> +}
> +
> +static int sc27xx_fgu_set_clbcnt(struct sc27xx_fgu_data *data, int clbcnt)
> +{
> +	int ret;
> +
> +	clbcnt *= SC27XX_FGU_SAMPLE_HZ;
> +
> +	ret = regmap_update_bits(data->regmap,
> +				 data->base + SC27XX_FGU_CLBCNT_SETL,
> +				 SC27XX_FGU_CLBCNT_MASK, clbcnt);
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_update_bits(data->regmap,
> +				 data->base + SC27XX_FGU_CLBCNT_SETH,
> +				 SC27XX_FGU_CLBCNT_MASK,
> +				 clbcnt >> SC27XX_FGU_CLBCNT_SHIFT);
> +	if (ret)
> +		return ret;
> +
> +	return regmap_update_bits(data->regmap, data->base + SC27XX_FGU_START,
> +				 SC27XX_WRITE_SELCLB_EN,
> +				 SC27XX_WRITE_SELCLB_EN);
> +}
> +
> +static int sc27xx_fgu_get_clbcnt(struct sc27xx_fgu_data *data, int *clb_cnt)
> +{
> +	int ccl, cch, ret;
> +
> +	ret = regmap_read(data->regmap, data->base + SC27XX_FGU_CLBCNT_VALL,
> +			  &ccl);
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_read(data->regmap, data->base + SC27XX_FGU_CLBCNT_VALH,
> +			  &cch);
> +	if (ret)
> +		return ret;
> +
> +	*clb_cnt = ccl & SC27XX_FGU_CLBCNT_MASK;
> +	*clb_cnt |= (cch & SC27XX_FGU_CLBCNT_MASK) << SC27XX_FGU_CLBCNT_SHIFT;
> +	*clb_cnt /= SC27XX_FGU_SAMPLE_HZ;
> +
> +	return 0;
> +}
> +
> +static int sc27xx_fgu_get_capacity(struct sc27xx_fgu_data *data, int *cap)
> +{
> +	int ret, cur_clbcnt, delta_clbcnt, delta_cap, temp;
> +
> +	/* Get current coulomb counters firstly */
> +	ret = sc27xx_fgu_get_clbcnt(data, &cur_clbcnt);
> +	if (ret)
> +		return ret;
> +
> +	delta_clbcnt = cur_clbcnt - data->init_clbcnt;
> +
> +	/*
> +	 * Convert coulomb counter to delta capacity (mAh), and set multiplier
> +	 * as 100 to improve the precision.
> +	 */
> +	temp = DIV_ROUND_CLOSEST(delta_clbcnt, 360);
> +	temp = sc27xx_fgu_adc_to_current(temp);
> +
> +	/*
> +	 * Convert to capacity percent of the battery total capacity,
> +	 * and multiplier is 100 too.
> +	 */
> +	delta_cap = DIV_ROUND_CLOSEST(temp * 100, data->total_cap);
> +	*cap = delta_cap + data->init_cap;
> +
> +	return 0;
> +}
> +
> +static int sc27xx_fgu_get_vbat_vol(struct sc27xx_fgu_data *data, int *val)
> +{
> +	int ret, vol;
> +
> +	ret = regmap_read(data->regmap, data->base + SC27XX_FGU_VOLTAGE, &vol);
> +	if (ret)
> +		return ret;
> +
> +	/*
> +	 * It is ADC values reading from registers which need to convert to
> +	 * corresponding voltage values.
> +	 */
> +	*val = sc27xx_fgu_adc_to_voltage(vol);
> +
> +	return 0;
> +}
> +
> +static int sc27xx_fgu_get_current(struct sc27xx_fgu_data *data, int *val)
> +{
> +	int ret, cur;
> +
> +	ret = regmap_read(data->regmap, data->base + SC27XX_FGU_CURRENT, &cur);
> +	if (ret)
> +		return ret;
> +
> +	/*
> +	 * It is ADC values reading from registers which need to convert to
> +	 * corresponding current values.
> +	 */
> +	*val = sc27xx_fgu_adc_to_current(cur - SC27XX_FGU_CUR_BASIC_ADC);
> +
> +	return 0;
> +}
> +
> +static int sc27xx_fgu_get_vbat_ocv(struct sc27xx_fgu_data *data, int *val)
> +{
> +	int vol, cur, ret;
> +
> +	ret = sc27xx_fgu_get_vbat_vol(data, &vol);
> +	if (ret)
> +		return ret;
> +
> +	ret = sc27xx_fgu_get_current(data, &cur);
> +	if (ret)
> +		return ret;
> +
> +	*val = vol - (cur * data->inner_resist) / 1000;

You multiply this with 1000 directly after this function to get back
to uV. Just drop the division and the multiplication.

> +
> +	return 0;
> +}
> +
> +static int sc27xx_fgu_get_temp(struct sc27xx_fgu_data *data, int *temp)
> +{
> +	return iio_read_channel_processed(data->channel, temp);
> +}
> +
> +static int sc27xx_fgu_get_health(struct sc27xx_fgu_data *data, int *health)
> +{
> +	int ret, vol;
> +
> +	ret = sc27xx_fgu_get_vbat_vol(data, &vol);
> +	if (ret)
> +		return ret;
> +
> +	if (vol > data->max_volt)
> +		*health = POWER_SUPPLY_HEALTH_OVERVOLTAGE;
> +	else
> +		*health = POWER_SUPPLY_HEALTH_GOOD;
> +
> +	return 0;
> +}
> +
> +static int sc27xx_fgu_get_status(struct sc27xx_fgu_data *data, int *status)
> +{
> +	union power_supply_propval val;
> +	struct power_supply *psy;
> +	int i, ret = -EINVAL;
> +
> +	for (i = 0; i < ARRAY_SIZE(sc27xx_charger_supply_name); i++) {
> +		psy = power_supply_get_by_name(sc27xx_charger_supply_name[i]);
> +		if (!psy)
> +			continue;
> +
> +		ret = power_supply_get_property(psy, POWER_SUPPLY_PROP_STATUS,
> +						&val);
> +		power_supply_put(psy);
> +		if (ret)
> +			return ret;
> +
> +		*status = val.intval;
> +	}
> +
> +	return ret;
> +}
> +
> +static int sc27xx_fgu_get_property(struct power_supply *psy,
> +				   enum power_supply_property psp,
> +				   union power_supply_propval *val)
> +{
> +	struct sc27xx_fgu_data *data = power_supply_get_drvdata(psy);
> +	int ret = 0;
> +	int value;
> +
> +	mutex_lock(&data->lock);
> +
> +	switch (psp) {
> +	case POWER_SUPPLY_PROP_STATUS:
> +		ret = sc27xx_fgu_get_status(data, &value);
> +		if (ret)
> +			goto error;
> +
> +		val->intval = value;
> +		break;
> +
> +	case POWER_SUPPLY_PROP_HEALTH:
> +		ret = sc27xx_fgu_get_health(data, &value);
> +		if (ret)
> +			goto error;
> +
> +		val->intval = value;
> +		break;
> +
> +	case POWER_SUPPLY_PROP_PRESENT:
> +		val->intval = data->bat_present;
> +		break;
> +
> +	case POWER_SUPPLY_PROP_TEMP:
> +		ret = sc27xx_fgu_get_temp(data, &value);
> +		if (ret)
> +			goto error;
> +
> +		val->intval = value;
> +		break;
> +
> +	case POWER_SUPPLY_PROP_TECHNOLOGY:
> +		val->intval = POWER_SUPPLY_TECHNOLOGY_LION;
> +		break;
> +
> +	case POWER_SUPPLY_PROP_CAPACITY:
> +		ret = sc27xx_fgu_get_capacity(data, &value);
> +		if (ret)
> +			goto error;
> +
> +		val->intval = value;
> +		break;
> +
> +	case POWER_SUPPLY_PROP_VOLTAGE_NOW:
> +		ret = sc27xx_fgu_get_vbat_vol(data, &value);
> +		if (ret)
> +			goto error;
> +
> +		val->intval = value * 1000;
> +		break;
> +
> +	case POWER_SUPPLY_PROP_VOLTAGE_OCV:
> +		ret = sc27xx_fgu_get_vbat_ocv(data, &value);
> +		if (ret)
> +			goto error;
> +
> +		val->intval = value * 1000;
> +		break;
> +
> +	case POWER_SUPPLY_PROP_CURRENT_NOW:
> +	case POWER_SUPPLY_PROP_CURRENT_AVG:
> +		ret = sc27xx_fgu_get_current(data, &value);
> +		if (ret)
> +			goto error;
> +
> +		val->intval = value * 1000;
> +		break;
> +
> +	default:
> +		ret = -EINVAL;
> +		break;
> +	}
> +
> +error:
> +	mutex_unlock(&data->lock);
> +	return ret;
> +}
> +
> +static void sc27xx_fgu_external_power_changed(struct power_supply *psy)
> +{
> +	struct sc27xx_fgu_data *data = power_supply_get_drvdata(psy);
> +
> +	power_supply_changed(data->battery);
> +}
> +
> +static enum power_supply_property sc27xx_fgu_props[] = {
> +	POWER_SUPPLY_PROP_STATUS,
> +	POWER_SUPPLY_PROP_HEALTH,
> +	POWER_SUPPLY_PROP_PRESENT,
> +	POWER_SUPPLY_PROP_TEMP,
> +	POWER_SUPPLY_PROP_TECHNOLOGY,
> +	POWER_SUPPLY_PROP_CAPACITY,
> +	POWER_SUPPLY_PROP_VOLTAGE_NOW,
> +	POWER_SUPPLY_PROP_VOLTAGE_OCV,
> +	POWER_SUPPLY_PROP_CURRENT_NOW,
> +	POWER_SUPPLY_PROP_CURRENT_AVG,
> +};
> +
> +static const struct power_supply_desc sc27xx_fgu_desc = {
> +	.name			= "sc27xx-fgu",
> +	.type			= POWER_SUPPLY_TYPE_BATTERY,
> +	.properties		= sc27xx_fgu_props,
> +	.num_properties		= ARRAY_SIZE(sc27xx_fgu_props),
> +	.get_property		= sc27xx_fgu_get_property,
> +	.external_power_changed	= sc27xx_fgu_external_power_changed,
> +};
> +
> +static irqreturn_t sc27xx_fgu_bat_detection(int irq, void *dev_id)
> +{
> +	struct sc27xx_fgu_data *data = dev_id;
> +	int state;
> +
> +	mutex_lock(&data->lock);
> +
> +	state = gpiod_get_value_cansleep(data->gpiod);
> +	if (state < 0) {
> +		dev_err(data->dev, "failed to get gpio state\n");
> +		mutex_unlock(&data->lock);
> +		return IRQ_RETVAL(state);
> +	}
> +
> +	if (state)
> +		data->bat_present = true;
> +	else
> +		data->bat_present = false;
> +
> +	mutex_unlock(&data->lock);

You want to call power_supply_changed() here.

> +	return IRQ_HANDLED;
> +}
> +
> +static void sc27xx_fgu_disable(void *_data)
> +{
> +	struct sc27xx_fgu_data *data = _data;
> +
> +	regmap_update_bits(data->regmap, SC27XX_CLK_EN0, SC27XX_FGU_RTC_EN, 0);
> +	regmap_update_bits(data->regmap, SC27XX_MODULE_EN0, SC27XX_FGU_EN, 0);
> +}
> +
> +static int sc27xx_fgu_cap_to_clbcnt(struct sc27xx_fgu_data *data, int capacity)
> +{
> +	/*
> +	 * Get current capacity (mAh) = battery total capacity (mAh) *
> +	 * current capacity percent (capacity / 100).
> +	 */
> +	int cur_cap = DIV_ROUND_CLOSEST(data->total_cap * capacity, 100);
> +
> +	/*
> +	 * Convert current capacity (mAh) to coulomb counter according to the
> +	 * formula: 1 mAh =3.6 coulomb.
> +	 */
> +	return DIV_ROUND_CLOSEST(cur_cap * 36, 10);
> +}
> +
> +static int sc27xx_fgu_hw_init(struct sc27xx_fgu_data *data)
> +{
> +	struct power_supply_battery_info info = { };
> +	int ret;
> +
> +	ret = power_supply_get_battery_info(data->battery, &info);
> +	if (ret) {
> +		dev_err(data->dev, "failed to get battery information\n");
> +		return ret;
> +	}
> +
> +	data->total_cap = info.charge_full_design_uah / 1000;
> +	data->max_volt = info.constant_charge_voltage_max_uv / 1000;
> +
> +	/* Enable the FGU module */
> +	ret = regmap_update_bits(data->regmap, SC27XX_MODULE_EN0,
> +				 SC27XX_FGU_EN, SC27XX_FGU_EN);
> +	if (ret) {
> +		dev_err(data->dev, "failed to enable fgu\n");
> +		return ret;
> +	}
> +
> +	/* Enable the FGU RTC clock to make it work */
> +	ret = regmap_update_bits(data->regmap, SC27XX_CLK_EN0,
> +				 SC27XX_FGU_RTC_EN, SC27XX_FGU_RTC_EN);
> +	if (ret) {
> +		dev_err(data->dev, "failed to enable fgu RTC clock\n");
> +		goto disable_fgu;
> +	}
> +
> +	/*
> +	 * Get the boot battery capacity when system powers on, which is used to
> +	 * initialize the coulomb counter. After that, we can read the coulomb
> +	 * counter to measure the battery capacity.
> +	 */
> +	ret = sc27xx_fgu_get_boot_capacity(data, &data->init_cap);
> +	if (ret) {
> +		dev_err(data->dev, "failed to get boot capacity\n");
> +		goto disable_clk;
> +	}
> +
> +	/*
> +	 * Convert battery capacity to the corresponding initial coulomb counter
> +	 * and set into coulomb counter registers.
> +	 */
> +	data->init_clbcnt = sc27xx_fgu_cap_to_clbcnt(data, data->init_cap);
> +	ret = sc27xx_fgu_set_clbcnt(data, data->init_clbcnt);
> +	if (ret) {
> +		dev_err(data->dev, "failed to initialize coulomb counter\n");
> +		goto disable_clk;
> +	}
> +
> +	return 0;
> +
> +disable_clk:
> +	regmap_update_bits(data->regmap, SC27XX_CLK_EN0, SC27XX_FGU_RTC_EN, 0);
> +disable_fgu:
> +	regmap_update_bits(data->regmap, SC27XX_MODULE_EN0, SC27XX_FGU_EN, 0);
> +
> +	return ret;
> +}
> +
> +static int sc27xx_fgu_parse_dt(struct sc27xx_fgu_data *data,
> +			       struct device_node *np)
> +{
> +	const __be32 *list;
> +	int i, len, size, ret;
> +
> +	ret = of_property_read_u32(np, "reg", &data->base);
> +	if (ret) {
> +		dev_err(data->dev, "failed to get fgu address\n");
> +		return ret;
> +	}
> +
> +	data->gpiod = devm_gpiod_get_optional(data->dev, "bat-detect", GPIOD_IN);
> +	if (IS_ERR(data->gpiod)) {
> +		dev_err(data->dev, "failed to get battery detection GPIO\n");
> +		return PTR_ERR(data->gpiod);
> +	}

According to the binding (and the remaining code!) this gpio is not
optional.

-- Sebastian

> +	data->channel = devm_iio_channel_get(data->dev, "bat-temp");
> +	if (IS_ERR(data->channel)) {
> +		dev_err(data->dev, "failed to get IIO channel\n");
> +		return PTR_ERR(data->channel);
> +	}
> +
> +	/* Get the battery inner resistance */
> +	ret = of_property_read_u32(np, "sprd,inner-resist", &data->inner_resist);
> +	if (ret) {
> +		dev_err(data->dev, "failed to get battery inner resistance\n");
> +		return ret;
> +	}
> +
> +	/* Get battery ocv-capacity table */
> +	list = of_get_property(np, "sprd,ocv-cap-table", &size);
> +	if (!list || !size) {
> +		dev_err(data->dev, "failed to get ocv-capacity table\n");
> +		return -EINVAL;
> +	}
> +
> +	len = size / 8;
> +	data->table_len = len;
> +	data->cap_table = devm_kzalloc(data->dev,
> +				sizeof(struct sc27xx_fgu_capacity_table) * len,
> +				GFP_KERNEL);
> +	if (!data->cap_table)
> +		return -ENOMEM;
> +
> +	for (i = 0; i < len; i++) {
> +		data->cap_table[i].ocv = be32_to_cpu(*list++);
> +		data->cap_table[i].capacity = be32_to_cpu(*list++);
> +	}
> +
> +	return 0;
> +}
> +
> +static int sc27xx_fgu_probe(struct platform_device *pdev)
> +{
> +	struct device_node *np = pdev->dev.of_node;
> +	struct power_supply_config fgu_cfg = { };
> +	struct sc27xx_fgu_data *data;
> +	int ret, irq;
> +
> +	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +
> +	data->regmap = dev_get_regmap(pdev->dev.parent, NULL);
> +	if (!data->regmap) {
> +		dev_err(&pdev->dev, "failed to get regmap\n");
> +		return -ENODEV;
> +	}
> +
> +	mutex_init(&data->lock);
> +	data->dev = &pdev->dev;
> +	data->bat_present = true;
> +
> +	ret = sc27xx_fgu_parse_dt(data, np);
> +	if (ret)
> +		return ret;
> +
> +	fgu_cfg.drv_data = data;
> +	fgu_cfg.of_node = np;
> +	data->battery = devm_power_supply_register(&pdev->dev, &sc27xx_fgu_desc,
> +						   &fgu_cfg);
> +	if (IS_ERR(data->battery)) {
> +		dev_err(&pdev->dev, "failed to register power supply\n");
> +		return PTR_ERR(data->battery);
> +	}
> +
> +	ret = sc27xx_fgu_hw_init(data);
> +	if (ret) {
> +		dev_err(&pdev->dev, "failed to initialize fgu hardware\n");
> +		return ret;
> +	}
> +
> +	ret = devm_add_action(&pdev->dev, sc27xx_fgu_disable, data);
> +	if (ret) {
> +		sc27xx_fgu_disable(data);
> +		dev_err(&pdev->dev, "failed to add fgu disable action\n");
> +		return ret;
> +	}
> +
> +	irq = gpiod_to_irq(data->gpiod);
> +	if (irq < 0) {
> +		dev_err(&pdev->dev, "failed to translate GPIO to IRQ\n");
> +		return irq;
> +	}
> +
> +	ret = devm_request_threaded_irq(&pdev->dev, irq, NULL,
> +					sc27xx_fgu_bat_detection,
> +					IRQF_ONESHOT | IRQF_TRIGGER_RISING |
> +					IRQF_TRIGGER_FALLING,
> +					pdev->name, data);
> +	if (ret) {
> +		dev_err(&pdev->dev, "failed to request IRQ\n");
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id sc27xx_fgu_of_match[] = {
> +	{ .compatible = "sprd,sc2731-fgu", },
> +	{ }
> +};
> +
> +static struct platform_driver sc27xx_fgu_driver = {
> +	.probe = sc27xx_fgu_probe,
> +	.driver = {
> +		.name = "sc27xx-fgu",
> +		.of_match_table = sc27xx_fgu_of_match,
> +	}
> +};
> +
> +module_platform_driver(sc27xx_fgu_driver);
> +
> +MODULE_DESCRIPTION("Spreadtrum SC27XX PMICs Fual Gauge Unit Driver");
> +MODULE_LICENSE("GPL v2");
> -- 
> 1.7.9.5
>

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