Message-ID: <20190426161039.GA6341@roeck-us.net>
Date:   Fri, 26 Apr 2019 09:10:39 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Andrey Smirnov <andrew.smirnov@...il.com>
Cc:     linux-pm@...r.kernel.org, Chris Health <cphealy@...il.com>,
        Lucas Stach <l.stach@...gutronix.de>,
        Fabio Estevam <fabio.estevam@....com>,
        Sebastian Reichel <sre@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] power: supply: Add driver for Microchip UCS1002

On Wed, Apr 17, 2019 at 01:44:56AM -0700, Andrey Smirnov wrote:
> Add driver for Microchip UCS1002 Programmable USB Port Power
> Controller with Charger Emulation. The driver exposed a power supply
> device to control/monitor various parameter of the device as well as a
> regulator to allow controlling VBUS line.
> 
> Signed-off-by: Andrey Smirnov <andrew.smirnov@...il.com>
> Cc: Chris Health <cphealy@...il.com>
> Cc: Lucas Stach <l.stach@...gutronix.de>
> Cc: Fabio Estevam <fabio.estevam@....com>
> Cc: Guenter Roeck <linux@...ck-us.net>
> Cc: Sebastian Reichel <sre@...nel.org>
> Cc: linux-kernel@...r.kernel.org
> Cc: linux-pm@...r.kernel.org
> ---
>  drivers/power/supply/Kconfig         |   9 +
>  drivers/power/supply/Makefile        |   1 +
>  drivers/power/supply/ucs1002_power.c | 639 +++++++++++++++++++++++++++
>  3 files changed, 649 insertions(+)
>  create mode 100644 drivers/power/supply/ucs1002_power.c
> 
> diff --git a/drivers/power/supply/Kconfig b/drivers/power/supply/Kconfig
> index e901b9879e7e..c614c8a196f3 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_UCS1002
> +        tristate "Microchip UCS1002 USB Port Power Controller"
> +	depends on I2C
> +	depends on OF
> +	select REGMAP_I2C
> +	help
> +	  Say Y to enable support for Microchip UCS1002 Programmable
> +	  USB Port Power Controller with Charger Emulation.
> +
>  endif # POWER_SUPPLY
> diff --git a/drivers/power/supply/Makefile b/drivers/power/supply/Makefile
> index b731c2a9b695..c56803a9e4fe 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_UCS1002)	+= ucs1002_power.o
> diff --git a/drivers/power/supply/ucs1002_power.c b/drivers/power/supply/ucs1002_power.c
> new file mode 100644
> index 000000000000..b0b81d62e003
> --- /dev/null
> +++ b/drivers/power/supply/ucs1002_power.c
> @@ -0,0 +1,639 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Driver for UCS1002 Programmable USB Port Power Controller
> + *
> + * Copyright (C) 2019 Zodiac Inflight Innovations
> + */
> +#include <linux/freezer.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/i2c.h>
> +#include <linux/interrupt.h>
> +#include <linux/kernel.h>
> +#include <linux/kthread.h>
> +#include <linux/device.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_irq.h>
> +#include <linux/power_supply.h>
> +#include <linux/regmap.h>
> +#include <linux/regulator/driver.h>
> +#include <linux/regulator/of_regulator.h>
> +
You probably want to include linux/bits.h as well.

> +/* UCS1002 Registers */
> +#define UCS1002_REG_CURRENT_MEASUREMENT	0x00
> +
> +/*
> + * The Total Accumulated Charge registers store the total accumulated
> + * charge delivered from the VS source to a portable device. The total
> + * value is calculated using four registers, from 01h to 04h. The bit
> + * weighting of the registers is given in mA/hrs.
> + */
> +#define UCS1002_REG_TOTAL_ACC_CHARGE	0x01
> +
> +/* Other Status Register */
> +#define UCS1002_REG_OTHER_STATUS	0x0f
> +#  define F_ADET_PIN			BIT(4)
> +#  define F_CHG_ACT			BIT(3)
> +
> +/* Interrupt Status */
> +#define UCS1002_REG_INTERRUPT_STATUS	0x10
> +#  define F_DISCHARGE_ERR		BIT(6)
> +#  define F_RESET			BIT(5)
> +#  define F_MIN_KEEP_OUT		BIT(4)
> +#  define F_TSD				BIT(3)
> +#  define F_OVER_VOLT			BIT(2)
> +#  define F_BACK_VOLT			BIT(1)
> +#  define F_OVER_ILIM			BIT(0)
> +
> +/* Pin Status Register */
> +#define UCS1002_REG_PIN_STATUS		0x14
> +#  define UCS1002_PWR_STATE_MASK	0x03
> +#  define F_PWR_EN_PIN			BIT(6)
> +#  define F_M2_PIN			BIT(5)
> +#  define F_M1_PIN			BIT(4)
> +#  define F_EM_EN_PIN			BIT(3)
> +#  define F_SEL_PIN			BIT(2)
> +#  define F_ACTIVE_MODE_MASK		GENMASK(5, 3)
> +#  define F_ACTIVE_MODE_PASSTHROUGH	F_M2_PIN
> +#  define F_ACTIVE_MODE_DEDICATED	F_EM_EN_PIN
> +#  define F_ACTIVE_MODE_BC12_DCP	(F_M2_PIN | F_EM_EN_PIN)
> +#  define F_ACTIVE_MODE_BC12_SDP	F_M1_PIN
> +#  define F_ACTIVE_MODE_BC12_CDP	(F_M1_PIN | F_M2_PIN | F_EM_EN_PIN)
> +
> +/* General Configuration Register */
> +#define UCS1002_REG_GENERAL_CFG		0x15
> +#  define F_RATION_EN			BIT(3)
> +
> +/* Emulation Configuration Register */
> +#define UCS1002_REG_EMU_CFG		0x16
> +
> +/* Switch Configuration Register */
> +#define UCS1002_REG_SWITCH_CFG		0x17
> +#  define F_PIN_IGNORE			BIT(7)
> +#  define F_EM_EN_SET			BIT(5)
> +#  define F_M2_SET			BIT(4)
> +#  define F_M1_SET			BIT(3)
> +#  define F_S0_SET			BIT(2)
> +#  define F_PWR_EN_SET			BIT(1)
> +#  define F_LATCH_SET			BIT(0)
> +#  define V_SET_ACTIVE_MODE_MASK	GENMASK(5, 3)
> +#  define V_SET_ACTIVE_MODE_PASSTHROUGH	F_M2_SET
> +#  define V_SET_ACTIVE_MODE_DEDICATED	F_EM_EN_SET
> +#  define V_SET_ACTIVE_MODE_BC12_DCP	(F_M2_SET | F_EM_EN_SET)
> +#  define V_SET_ACTIVE_MODE_BC12_SDP	F_M1_SET
> +#  define V_SET_ACTIVE_MODE_BC12_CDP	(F_M1_SET | F_M2_SET | F_EM_EN_SET)
> +
> +/* Current Limit Register */
> +#define UCS1002_REG_ILIMIT		0x19
> +#  define UCS1002_ILIM_SW_MASK		GENMASK(3, 0)
> +
> +/* Product ID */
> +#define UCS1002_REG_PRODUCT_ID		0xfd
> +#  define UCS1002_PRODUCT_ID		0x4e
> +
> +/* Manufacture name */
> +#define UCS1002_MANUFACTURER		"SMSC"
> +
> +struct ucs1002_info {
> +	struct power_supply *charger;
> +	struct i2c_client *client;
> +	struct regmap *regmap;
> +	struct regulator_desc *regulator_descriptor;
> +	bool present;
> +};
> +
> +static enum power_supply_property ucs1002_props[] = {
> +	POWER_SUPPLY_PROP_ONLINE,
> +	POWER_SUPPLY_PROP_CHARGE_NOW,
> +	POWER_SUPPLY_PROP_CURRENT_NOW,
> +	POWER_SUPPLY_PROP_CURRENT_MAX,
> +	POWER_SUPPLY_PROP_PRESENT, /* the presence of PED */
> +	POWER_SUPPLY_PROP_MANUFACTURER,
> +	POWER_SUPPLY_PROP_USB_TYPE,
> +	POWER_SUPPLY_PROP_HEALTH,
> +};
> +
> +static int ucs1002_get_online(struct ucs1002_info *info,
> +			      union power_supply_propval *val)
> +{
> +	unsigned int reg;
> +	int ret;
> +
> +	ret = regmap_read(info->regmap, UCS1002_REG_OTHER_STATUS, &reg);
> +	if (ret)
> +		return ret;
> +
> +	val->intval = !!(reg & F_CHG_ACT);
> +
> +	return 0;
> +}
> +
> +static int ucs1002_get_charge(struct ucs1002_info *info,
> +			      union power_supply_propval *val)
> +{
> +	/*
> +	 * To fit within 32 bits some values are rounded (uA/h)
> +	 *
> +	 * For Total Accumulated Charge Middle Low Byte register, addr
> +	 * 03h, byte 2
> +	 *
> +	 *   B0: 0.01084 mA/h rounded to 11 uA/h
> +	 *   B1: 0.02169 mA/h rounded to 22 uA/h
> +	 *   B2: 0.04340 mA/h rounded to 43 uA/h
> +	 *   B3: 0.08676 mA/h rounded to 87 uA/h
> +	 *   B4: 0.17350 mA/h rounded to 173 uÁ/h
> +	 *
> +	 * For Total Accumulated Charge Low Byte register, addr 04h,
> +	 * byte 3
> +	 *
> +	 *   B6: 0.00271 mA/h rounded to 3 uA/h
> +	 *   B7: 0.005422 mA/h rounded to 5 uA/h
> +	 */
> +	static const int bit_weights_uAh[BITS_PER_TYPE(u32)] = {
> +		0, 0, 0, 0, 0, 0, 3, 5,
> +
> +		11, 22, 43, 87, 173, 347, 694, 1388,
> +
> +		2776, 5552, 11105, 22210, 44420, 88840, 177700, 355400,
> +
> +		710700, 1421000, 2843000, 5685000, 11371000, 22742000,
> +		45484000, 90968000,
> +	};
> +	unsigned long total_acc_charger;
> +	unsigned int reg;
> +	int i, ret;
> +
> +	ret = regmap_bulk_read(info->regmap, UCS1002_REG_TOTAL_ACC_CHARGE,
> +			       &reg, sizeof(u32));
> +	if (ret)
> +		return ret;
> +
> +	total_acc_charger = be32_to_cpu(reg);
> +	val->intval = 0;
> +
> +	for_each_set_bit(i, &total_acc_charger, ARRAY_SIZE(bit_weights_uAh))
> +		val->intval += bit_weights_uAh[i];
> +
> +	return 0;
> +}
> +
> +static int ucs1002_get_current(struct ucs1002_info *info,
> +			       union power_supply_propval *val)
> +{
> +	/*
> +	 * The Current Measurement register stores the measured
> +	 * current value delivered to the portable device. The range
> +	 * is from 9.76 mA to 2.5 A.
> +	 */
> +	static const int bit_weights_uA[BITS_PER_TYPE(u8)] = {
> +		9760, 19500, 39000, 78100, 156200, 312300, 624600, 1249300,
> +	};
> +	unsigned long current_measurement;
> +	unsigned int reg;
> +	int i, ret;
> +
> +	ret = regmap_read(info->regmap, UCS1002_REG_CURRENT_MEASUREMENT, &reg);
> +	if (ret)
> +		return ret;
> +
> +	current_measurement = reg;
> +	val->intval = 0;
> +
> +	for_each_set_bit(i, &current_measurement, ARRAY_SIZE(bit_weights_uA))
> +		val->intval += bit_weights_uA[i];
> +
> +	return 0;
> +}
> +
> +/*
> + * The Current Limit register stores the maximum current used by the
> + * port switch. The range is from 500mA to 2.5 A.
> + */
> +static const u32 ucs1002_current_limit_uA[] = {
> +	500000, 900000, 1000000, 1200000, 1500000, 1800000, 2000000, 2500000,
> +};
> +
> +static int ucs1002_get_max_current(struct ucs1002_info *info,
> +				   union power_supply_propval *val)
> +{
> +	unsigned int reg;
> +	int ret;
> +
> +	ret = regmap_read(info->regmap, UCS1002_REG_ILIMIT, &reg);
> +	if (ret)
> +		return ret;
> +
> +	val->intval = ucs1002_current_limit_uA[reg & UCS1002_ILIM_SW_MASK];
> +
> +	return 0;
> +}
> +
> +static int ucs1002_set_max_current(struct ucs1002_info *info, u32 val)
> +{
> +	unsigned int reg;
> +	int ret, idx;
> +
> +	for (idx = 0; idx < ARRAY_SIZE(ucs1002_current_limit_uA); idx++) {
> +		if (val == ucs1002_current_limit_uA[idx])
> +			break;
> +	}
> +
> +	if (idx == ARRAY_SIZE(ucs1002_current_limit_uA)) {
> +		dev_err(&info->client->dev,
> +			"%d is an invalid max current value\n", val);

Here the error message is displayed as result of an attempt to set the current
limit, which presumably can happen from userspace. This is inconsistent with
the error returns below. I am not sure I understand why this would warrant an
error log, but exceeding the limit set with the ILIM pin doesn't. I would
suggest to drop this error message.

> +		return -EINVAL;
> +	}
> +
> +	ret = regmap_write(info->regmap, UCS1002_REG_ILIMIT, idx);
> +	if (ret)
> +		return ret;
> +	/*
> +	 * Any current limit setting exceeding the one set via ILIM
> +	 * pin will be rejected, so we read out freshly changed limit
> +	 * to make sure that it took effect.
> +	 */
> +	ret = regmap_read(info->regmap, UCS1002_REG_ILIMIT, &reg);
> +	if (ret)
> +		return ret;
> +
> +	if (reg != idx)
> +		return -EINVAL;
> +
> +	return 0;
> +}
> +
> +static enum power_supply_usb_type ucs1002_usb_types[] = {
> +	POWER_SUPPLY_USB_TYPE_PD,
> +	POWER_SUPPLY_USB_TYPE_SDP,
> +	POWER_SUPPLY_USB_TYPE_DCP,
> +	POWER_SUPPLY_USB_TYPE_CDP,
> +	POWER_SUPPLY_USB_TYPE_UNKNOWN,
> +};
> +
> +static int ucs1002_set_usb_type(struct ucs1002_info *info, int val)
> +{
> +	unsigned int mode;
> +
> +	if (val >= ARRAY_SIZE(ucs1002_usb_types))
> +		return -EINVAL;
> +
> +	switch (ucs1002_usb_types[val]) {
> +	case POWER_SUPPLY_USB_TYPE_PD:
> +		mode = V_SET_ACTIVE_MODE_DEDICATED;
> +		break;
> +	case POWER_SUPPLY_USB_TYPE_SDP:
> +		mode = V_SET_ACTIVE_MODE_BC12_SDP;
> +		break;
> +	case POWER_SUPPLY_USB_TYPE_DCP:
> +		mode = V_SET_ACTIVE_MODE_BC12_DCP;
> +		break;
> +	case POWER_SUPPLY_USB_TYPE_CDP:
> +		mode = V_SET_ACTIVE_MODE_BC12_CDP;
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	return regmap_update_bits(info->regmap, UCS1002_REG_SWITCH_CFG,
> +				  V_SET_ACTIVE_MODE_MASK, mode);
> +}
> +
> +static int ucs1002_get_usb_type(struct ucs1002_info *info,
> +				union power_supply_propval *val)
> +{
> +	enum power_supply_usb_type type;
> +	unsigned int reg;
> +	int ret;
> +
> +	ret = regmap_read(info->regmap, UCS1002_REG_PIN_STATUS, &reg);
> +	if (ret)
> +		return ret;
> +
> +	switch (reg & F_ACTIVE_MODE_MASK) {
> +	default:
> +		type = POWER_SUPPLY_USB_TYPE_UNKNOWN;
> +		break;
> +	case F_ACTIVE_MODE_DEDICATED:
> +		type = POWER_SUPPLY_USB_TYPE_PD;
> +		break;
> +	case F_ACTIVE_MODE_BC12_SDP:
> +		type = POWER_SUPPLY_USB_TYPE_SDP;
> +		break;
> +	case F_ACTIVE_MODE_BC12_DCP:
> +		type = POWER_SUPPLY_USB_TYPE_DCP;
> +		break;
> +	case F_ACTIVE_MODE_BC12_CDP:
> +		type = POWER_SUPPLY_USB_TYPE_CDP;
> +		break;
> +	};
> +
> +	val->intval = type;
> +
> +	return 0;
> +}
> +
> +static int ucs1002_get_health(struct ucs1002_info *info,
> +			      union power_supply_propval *val)
> +{
> +	unsigned int reg;
> +	int ret, health;
> +
> +	ret = regmap_read(info->regmap, UCS1002_REG_INTERRUPT_STATUS, &reg);
> +	if (ret)
> +		return ret;
> +
> +	if (reg & F_TSD)
> +		health = POWER_SUPPLY_HEALTH_OVERHEAT;
> +	else if (reg & (F_OVER_VOLT | F_BACK_VOLT))
> +		health = POWER_SUPPLY_HEALTH_OVERVOLTAGE;
> +	else if (reg & F_OVER_ILIM)
> +		health = POWER_SUPPLY_HEALTH_OVERCURRENT;
> +	else if (reg & (F_DISCHARGE_ERR | F_MIN_KEEP_OUT))
> +		health = POWER_SUPPLY_HEALTH_UNSPEC_FAILURE;
> +	else
> +		health = POWER_SUPPLY_HEALTH_GOOD;
> +
> +	val->intval = health;
> +
> +	return 0;
> +}
> +
> +static int ucs1002_get_property(struct power_supply *psy,
> +				enum power_supply_property psp,
> +				union power_supply_propval *val)
> +{
> +	struct ucs1002_info *info = power_supply_get_drvdata(psy);
> +
> +	switch (psp) {
> +	case POWER_SUPPLY_PROP_ONLINE:
> +		return ucs1002_get_online(info, val);
> +	case POWER_SUPPLY_PROP_CHARGE_NOW:
> +		return ucs1002_get_charge(info, val);
> +	case POWER_SUPPLY_PROP_CURRENT_NOW:
> +		return ucs1002_get_current(info, val);
> +	case POWER_SUPPLY_PROP_CURRENT_MAX:
> +		return ucs1002_get_max_current(info, val);
> +	case POWER_SUPPLY_PROP_USB_TYPE:
> +		return ucs1002_get_usb_type(info, val);
> +	case POWER_SUPPLY_PROP_HEALTH:
> +		return ucs1002_get_health(info, val);
> +	case POWER_SUPPLY_PROP_PRESENT:
> +		val->intval = info->present;
> +		return 0;
> +	case POWER_SUPPLY_PROP_MANUFACTURER:
> +		val->strval = UCS1002_MANUFACTURER;
> +		return 0;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static int ucs1002_set_property(struct power_supply *psy,
> +				enum power_supply_property psp,
> +				const union power_supply_propval *val)
> +{
> +	struct ucs1002_info *info = power_supply_get_drvdata(psy);
> +
> +	switch (psp) {
> +	case POWER_SUPPLY_PROP_CURRENT_MAX:
> +		return ucs1002_set_max_current(info, val->intval);
> +	case POWER_SUPPLY_PROP_USB_TYPE:
> +		return ucs1002_set_usb_type(info, val->intval);
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static int ucs1002_property_is_writeable(struct power_supply *psy,
> +					 enum power_supply_property psp)
> +{
> +	switch (psp) {
> +	case POWER_SUPPLY_PROP_CURRENT_MAX:
> +	case POWER_SUPPLY_PROP_USB_TYPE:
> +		return true;
> +	default:
> +		return false;
> +	}
> +}
> +
> +static const struct power_supply_desc ucs1002_charger_desc = {
> +	.name			= "ucs1002",
> +	.type			= POWER_SUPPLY_TYPE_USB,
> +	.usb_types		= ucs1002_usb_types,
> +	.num_usb_types		= ARRAY_SIZE(ucs1002_usb_types),
> +	.get_property		= ucs1002_get_property,
> +	.set_property		= ucs1002_set_property,
> +	.property_is_writeable	= ucs1002_property_is_writeable,
> +	.properties		= ucs1002_props,
> +	.num_properties		= ARRAY_SIZE(ucs1002_props),
> +};
> +
> +static irqreturn_t ucs1002_charger_irq(int irq, void *data)
> +{
> +	int ret, regval;
> +	bool present;
> +	struct ucs1002_info *info = data;
> +
> +	present = info->present;
> +
> +	ret = regmap_read(info->regmap, UCS1002_REG_OTHER_STATUS, &regval);
> +	if (ret)
> +		return IRQ_HANDLED;
> +
> +	/* update attached status */
> +	info->present = (regval & F_ADET_PIN) ? true : false;

			!!(regval & F_ADET_PIN);

would do.

> +
> +	/* notify the change */
> +	if (present != info->present)
> +		power_supply_changed(info->charger);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static irqreturn_t ucs1002_alert_irq(int irq, void *data)
> +{
> +	struct ucs1002_info *info = data;
> +
> +	power_supply_changed(info->charger);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static const struct regulator_ops ucs1002_regulator_ops = {
> +	.is_enabled	= regulator_is_enabled_regmap,
> +	.enable		= regulator_enable_regmap,
> +	.disable	= regulator_disable_regmap,
> +};
> +
> +static const struct regulator_desc ucs1002_regulator_descriptor = {
> +	.name		= "ucs1002-vbus",
> +	.ops		= &ucs1002_regulator_ops,
> +	.type		= REGULATOR_VOLTAGE,
> +	.owner		= THIS_MODULE,
> +	.enable_reg	= UCS1002_REG_SWITCH_CFG,
> +	.enable_mask	= F_PWR_EN_SET,
> +	.enable_val	= F_PWR_EN_SET,
> +	.fixed_uV	= 5000000,
> +	.n_voltages	= 1,
> +};
> +
> +static int ucs1002_probe(struct i2c_client *client,
> +			 const struct i2c_device_id *dev_id)
> +{
> +	struct device *dev = &client->dev;
> +	struct power_supply_config charger_config = {};
> +	const struct regmap_config regmap_config = {
> +		.reg_bits = 8,
> +		.val_bits = 8,
> +	};
> +	struct regulator_config regulator_config = {};
> +	int irq_a_det, irq_alert, ret;
> +	struct regulator_dev *rdev;
> +	struct ucs1002_info *info;
> +	unsigned int regval;
> +
> +	info = devm_kzalloc(dev, sizeof(*info), GFP_KERNEL);
> +	if (!info)
> +		return -ENOMEM;
> +
> +	info->regmap = devm_regmap_init_i2c(client, &regmap_config);
> +	if (IS_ERR(info->regmap)) {
> +		ret = PTR_ERR(info->regmap);
> +		dev_err(dev, "regmap initialization failed: %d\n", ret);
> +		return ret;
> +	}
> +
> +	info->client = client;
> +
> +	irq_a_det = of_irq_get_byname(dev->of_node, "a_det");
> +	irq_alert = of_irq_get_byname(dev->of_node, "alert");
> +
> +	charger_config.of_node = dev->of_node;
> +	charger_config.drv_data = info;
> +
> +	ret = regmap_read(info->regmap, UCS1002_REG_PRODUCT_ID, &regval);
> +	if (ret)
> +		return ret;

Silent error ?

> +
> +	if (regval != UCS1002_PRODUCT_ID) {
> +		dev_err(dev,
> +			"Product ID does not match (0x%02x != 0x%02x)\n",
> +			regval, UCS1002_PRODUCT_ID);
> +		return -ENODEV;
> +	}
> +
> +	dev_info(dev, "registered with product id 0x%02x\n", regval);
> +
Does that add any value ? After all, the displayed value is known to be
UCS1002_PRODUCT_ID. It is also not really registered yet at this point.

> +	/* Enable charge rationing by default */
> +	ret = regmap_update_bits(info->regmap, UCS1002_REG_GENERAL_CFG,
> +				 F_RATION_EN, F_RATION_EN);
> +	if (ret)
> +		return ret;

Another silent error ? Seems odd, especially since we just above
already claimed that the device was registered.

> +
> +	dev_dbg(dev, "set active mode selection through i2c\n");
> +	/*
> +	 * Ignore the M1, M2, PWR_EN, and EM_EN pin states. Set active
> +	 * mode selection to Dedicated Charger Emulation Cycle.
> +	 *
> +	 * #M1    #M2    EM_EN
> +	 *  0      0       1   - Dedicated Charger Emulation Cycle
> +	 *
> +	 */
> +	ret = regmap_update_bits(info->regmap, UCS1002_REG_SWITCH_CFG,
> +				 F_PIN_IGNORE | F_EM_EN_SET | F_M2_SET |
> +				 F_M1_SET, F_PIN_IGNORE | F_EM_EN_SET);
> +	if (ret)
> +		return ret;

And another one.

> +	/*
> +	 * Be safe and set initial current limit to 500mA
> +	 */
> +	ret = ucs1002_set_max_current(info, 500000);
> +	if (ret) {
> +		dev_err(dev, "Failed to read max current default\n");

read ?

> +		return ret;
> +	}
> +
> +	info->charger = devm_power_supply_register(dev, &ucs1002_charger_desc,
> +						   &charger_config);
> +	if (IS_ERR(info->charger)) {
> +		dev_err(dev, "failed to register power supply\n");
> +		return PTR_ERR(info->charger);
> +	}
> +
> +	ret = regmap_read(info->regmap, UCS1002_REG_PIN_STATUS, &regval);
> +	if (ret)
> +		return ret;
> +
> +	info->regulator_descriptor =
> +		devm_kmemdup(dev, &ucs1002_regulator_descriptor,
> +			     sizeof(ucs1002_regulator_descriptor),
> +			     GFP_KERNEL);

What if devm_kmemdup() returns NULL ?

> +	info->regulator_descriptor->enable_is_inverted = !(regval & F_SEL_PIN);
> +
> +	regulator_config.dev = dev;
> +	regulator_config.of_node = dev->of_node;
> +	regulator_config.regmap = info->regmap;
> +
> +	rdev = devm_regulator_register(dev, info->regulator_descriptor,
> +				       &regulator_config);
> +	if (IS_ERR(rdev)) {
> +		dev_err(dev, "failed to register VBUS regulator\n");
> +		return PTR_ERR(rdev);
> +	}
> +
> +	if (irq_a_det > 0) {
> +		ret = devm_request_threaded_irq(dev, irq_a_det, NULL,
> +						ucs1002_charger_irq,
> +						IRQF_TRIGGER_FALLING |
> +						IRQF_TRIGGER_RISING |
> +						IRQF_ONESHOT,
> +						"ucs1002-a_det", info);
> +		if (ret) {
> +			dev_err(dev, "failed to request A_DET threaded irq\n");
> +			return ret;
> +		}
> +	}
> +
> +	if (irq_alert > 0) {
> +		ret = devm_request_threaded_irq(dev, irq_alert, NULL,
> +						ucs1002_alert_irq,
> +						IRQF_TRIGGER_FALLING |
> +						IRQF_TRIGGER_RISING |
> +						IRQF_ONESHOT,
> +						"ucs1002-alert", info);
> +		if (ret) {
> +			dev_err(dev, "failed to request ALERT threaded irq\n");
> +			return ret;
> +		}
> +	}
> +
> +	return 0;
> +}
> +
> +#if IS_ENABLED(CONFIG_OF)
> +static const struct of_device_id ucs1002_of_match[] = {
> +	{ .compatible = "microchip,ucs1002", },
> +	{ /* sentinel */ },
> +};
> +MODULE_DEVICE_TABLE(of, ucs1002_of_match);
> +#endif
> +
> +static const struct i2c_device_id ucs1002_ids[] = {
> +	{"ucs1002", 0},
> +	{ /* sentinel */ },
> +};
> +MODULE_DEVICE_TABLE(i2c, ucs1002_ids);
> +
> +static struct i2c_driver ucs1002_driver = {
> +	.driver = {
> +		   .name = "ucs1002",
> +		   .of_match_table = of_match_ptr(ucs1002_of_match),
> +	},
> +	.probe = ucs1002_probe,
> +};
> +module_i2c_driver(ucs1002_driver);
> +
> +MODULE_DESCRIPTION("Microchip UCS1002 Programmable USB Port Power Controller");
> +MODULE_AUTHOR("Enric Balletbo Serra <enric.balletbo@...labora.com>");
> +MODULE_AUTHOR("Andrey Smirnov <andrew.smirnov@...il.com>");
> +MODULE_LICENSE("GPL v2");
> -- 
> 2.20.1
> 

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