[v4,2/2] drivers: hwmon: ltc2991: add driver support

  Add support for LTC2991 Octal I2C Voltage, Current, and Temperature
Monitor.

The LTC2991 is used to monitor system temperatures, voltages and
currents. Through the I2C serial interface, the eight monitors can
individually measure supply voltages and can be paired for
differential measurements of current sense resistors or temperature
sensing transistors. Additional measurements include internal
temperature and internal VCC.

Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
---
changes in v4:
 - rework ltc2991_read_reg
 - remove labels
 - rework channel exposure according to datasheet part typical apllications
 - avoid division by 0 by checking property value
 Documentation/hwmon/index.rst   |   1 +
 Documentation/hwmon/ltc2991.rst |  43 ++++
 MAINTAINERS                     |   8 +
 drivers/hwmon/Kconfig           |  11 +
 drivers/hwmon/Makefile          |   1 +
 drivers/hwmon/ltc2991.c         | 437 ++++++++++++++++++++++++++++++++
 6 files changed, 501 insertions(+)
 create mode 100644 Documentation/hwmon/ltc2991.rst
 create mode 100644 drivers/hwmon/ltc2991.c
  

On Thu, Oct 12, 2023 at 01:29:36PM +0300, Antoniu Miclaus wrote:
> Add support for LTC2991 Octal I2C Voltage, Current, and Temperature
> Monitor.
> 
> The LTC2991 is used to monitor system temperatures, voltages and
> currents. Through the I2C serial interface, the eight monitors can
> individually measure supply voltages and can be paired for
> differential measurements of current sense resistors or temperature
> sensing transistors. Additional measurements include internal
> temperature and internal VCC.
> 
> Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
> ---
> changes in v4:
>  - rework ltc2991_read_reg
>  - remove labels
>  - rework channel exposure according to datasheet part typical apllications
>  - avoid division by 0 by checking property value
>  Documentation/hwmon/index.rst   |   1 +
>  Documentation/hwmon/ltc2991.rst |  43 ++++
>  MAINTAINERS                     |   8 +
>  drivers/hwmon/Kconfig           |  11 +
>  drivers/hwmon/Makefile          |   1 +
>  drivers/hwmon/ltc2991.c         | 437 ++++++++++++++++++++++++++++++++
>  6 files changed, 501 insertions(+)
>  create mode 100644 Documentation/hwmon/ltc2991.rst
>  create mode 100644 drivers/hwmon/ltc2991.c
> 
> diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
> index 88dadea85cfc..0ec96abe3f7d 100644
> --- a/Documentation/hwmon/index.rst
> +++ b/Documentation/hwmon/index.rst
> @@ -121,6 +121,7 @@ Hardware Monitoring Kernel Drivers
>     ltc2947
>     ltc2978
>     ltc2990
> +   ltc2991
>     ltc3815
>     ltc4151
>     ltc4215
> diff --git a/Documentation/hwmon/ltc2991.rst b/Documentation/hwmon/ltc2991.rst
> new file mode 100644
> index 000000000000..9ab29dd85012
> --- /dev/null
> +++ b/Documentation/hwmon/ltc2991.rst
> @@ -0,0 +1,43 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +Kernel driver ltc2991
> +=====================
> +
> +Supported chips:
> +
> +  * Analog Devices LTC2991
> +
> +    Prefix: 'ltc2991'
> +
> +    Addresses scanned: I2C 0x48 - 0x4f
> +
> +    Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/2991ff.pdf
> +
> +Authors:
> +
> +  - Antoniu Miclaus <antoniu.miclaus@analog.com>
> +
> +
> +Description
> +-----------
> +
> +This driver supports hardware monitoring for Analog Devices LTC2991 Octal I2C
> +Voltage, Current and Temperature Monitor.
> +
> +The LTC2991 is used to monitor system temperatures, voltages and currents.
> +Through the I2C serial interface, the eight monitors can individually measure
> +supply voltages and can be paired for differential measurements of current sense
> +resistors or temperature sensing transistors. Additional measurements include
> +internal temperatureand internal VCC.
> +
> +
> +sysfs-Interface
> +-------------
> +
> +The following attributes are supported. Limits are read-only.
> +
> +=============== =================
> +inX_input:      voltage input
> +currX_input:    current input
> +tempX_input:    temperature input
> +=============== =================
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 6c4cce45a09d..edfa49c42848 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -12449,6 +12449,14 @@ F:	drivers/hwmon/ltc2947-i2c.c
>  F:	drivers/hwmon/ltc2947-spi.c
>  F:	drivers/hwmon/ltc2947.h
>  
> +LTC2991 HARDWARE MONITOR DRIVER
> +M:	Antoniu Miclaus <antoniu.miclaus@analog.com>
> +L:	linux-hwmon@vger.kernel.org
> +S:	Supported
> +W:	https://ez.analog.com/linux-software-drivers
> +F:	Documentation/devicetree/bindings/hwmon/adi,ltc2991.yaml
> +F:	drivers/hwmon/ltc2991.c
> +
>  LTC2983 IIO TEMPERATURE DRIVER
>  M:	Nuno Sá <nuno.sa@analog.com>
>  L:	linux-iio@vger.kernel.org
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index ec38c8892158..818a67328fcd 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -932,6 +932,17 @@ config SENSORS_LTC2990
>  	  This driver can also be built as a module. If so, the module will
>  	  be called ltc2990.
>  
> +config SENSORS_LTC2991
> +	tristate "Analog Devices LTC2991"
> +	depends on I2C
> +	help
> +	  If you say yes here you get support for Analog Devices LTC2991
> +	  Octal I2C Voltage, Current, and Temperature Monitor. The LTC2991
> +	  supports a combination of voltage, current and temperature monitoring.
> +
> +	  This driver can also be built as a module. If so, the module will
> +	  be called ltc2991.
> +
>  config SENSORS_LTC2992
>  	tristate "Linear Technology LTC2992"
>  	depends on I2C
> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> index 4ac9452b5430..f324d057535a 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -127,6 +127,7 @@ obj-$(CONFIG_SENSORS_LTC2947)	+= ltc2947-core.o
>  obj-$(CONFIG_SENSORS_LTC2947_I2C) += ltc2947-i2c.o
>  obj-$(CONFIG_SENSORS_LTC2947_SPI) += ltc2947-spi.o
>  obj-$(CONFIG_SENSORS_LTC2990)	+= ltc2990.o
> +obj-$(CONFIG_SENSORS_LTC2991)	+= ltc2991.o
>  obj-$(CONFIG_SENSORS_LTC2992)	+= ltc2992.o
>  obj-$(CONFIG_SENSORS_LTC4151)	+= ltc4151.o
>  obj-$(CONFIG_SENSORS_LTC4215)	+= ltc4215.o
> diff --git a/drivers/hwmon/ltc2991.c b/drivers/hwmon/ltc2991.c
> new file mode 100644
> index 000000000000..4f3d73bc494a
> --- /dev/null
> +++ b/drivers/hwmon/ltc2991.c
> @@ -0,0 +1,437 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2023 Analog Devices, Inc.
> + * Author: Antoniu Miclaus <antoniu.miclaus@analog.com>
> + */
> +
> +#include <linux/bitops.h>
> +#include <linux/err.h>
> +#include <linux/hwmon.h>
> +#include <linux/hwmon-sysfs.h>

I don't see why this include file would be needed.

> +#include <linux/i2c.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/property.h>
> +#include <linux/regmap.h>
> +#include <linux/regulator/consumer.h>
> +
> +#include <asm/unaligned.h>

There are no unaligned accesses, so it appears
that this include is not needed either.

> +
> +#define LTC2991_STATUS_LOW		0x00
> +#define LTC2991_CH_EN_TRIGGER		0x01
> +#define LTC2991_V1_V4_CTRL		0x06
> +#define LTC2991_V5_V8_CTRL		0x07
> +#define LTC2991_PWM_TH_LSB_T_INT	0x08
> +#define LTC2991_PWM_TH_MSB		0x09
> +#define LTC2991_CHANNEL_V_MSB(x)	(0x0A + ((x) * 2))
> +#define LTC2991_CHANNEL_T_MSB(x)	(0x0A + ((x) * 4))
> +#define LTC2991_CHANNEL_C_MSB(x)	(0x0C + ((x) * 4))
> +#define LTC2991_T_INT_MSB		0x1A
> +#define LTC2991_VCC_MSB			0x1C
> +
> +#define LTC2991_V7_V8_EN		BIT(7)
> +#define LTC2991_V5_V6_EN		BIT(6)
> +#define LTC2991_V3_V4_EN		BIT(5)
> +#define LTC2991_V1_V2_EN		BIT(4)
> +#define LTC2991_T_INT_VCC_EN		BIT(3)
> +
> +#define LTC2991_V3_V4_FILT_EN		BIT(7)
> +#define LTC2991_V3_V4_TEMP_EN		BIT(5)
> +#define LTC2991_V3_V4_DIFF_EN		BIT(4)
> +#define LTC2991_V1_V2_FILT_EN		BIT(3)
> +#define LTC2991_V1_V2_TEMP_EN		BIT(1)
> +#define LTC2991_V1_V2_DIFF_EN		BIT(0)
> +
> +#define LTC2991_V7_V8_FILT_EN		BIT(7)
> +#define LTC2991_V7_V8_TEMP_EN		BIT(5)
> +#define LTC2991_V7_V8_DIFF_EN		BIT(4)
> +#define LTC2991_V5_V6_FILT_EN		BIT(7)
> +#define LTC2991_V5_V6_TEMP_EN		BIT(5)
> +#define LTC2991_V5_V6_DIFF_EN		BIT(4)
> +
> +#define LTC2991_REPEAT_ACQ_EN		BIT(4)
> +#define LTC2991_T_INT_FILT_EN		BIT(3)
> +
> +#define LTC2991_MAX_CHANNEL		4
> +#define LTC2991_T_INT_CH_NR		4
> +#define LTC2991_VCC_CH_NR		0
> +
> +struct ltc2991_state {
> +	struct i2c_client	*client;

This is only used in the init function, and each time it is used
it is derefernced as &st->client->dev. Just pass dev as parameter
and be done with it.

> +	struct regmap		*regmap;
> +	u32			r_sense_uohm[LTC2991_MAX_CHANNEL];
> +	bool			temp_en[LTC2991_MAX_CHANNEL];
> +};
> +
> +static int ltc2991_read_reg(struct ltc2991_state *st, u8 addr, u8 reg_len,
> +			    int *val)
> +{
> +	__be16 regvals;
> +	int ret;
> +
> +	if (reg_len < 2)
> +		return regmap_read(st->regmap, addr, val);
> +
> +	ret = regmap_bulk_read(st->regmap, addr, &regvals, reg_len);
> +	if (ret)
> +		return ret;
> +
> +	*val = be16_to_cpu(regvals);
> +
> +	return 0;
> +}
> +
> +static int ltc2991_get_voltage(struct ltc2991_state *st, u32 reg, long *val)
> +{
> +	int reg_val, ret, offset = 0;
> +
> +	ret = ltc2991_read_reg(st, reg, 2, &reg_val);
> +	if (ret)
> +		return ret;
> +
> +	if (reg == LTC2991_VCC_MSB)
> +		/* Vcc 2.5V offset */
> +		offset = 2500;
> +
> +	/* Vx, 305.18uV/LSB */
> +	*val = DIV_ROUND_CLOSEST(sign_extend32(reg_val, 14) * 30518,
> +				 1000 * 100) + offset;
> +
> +	return 0;
> +}
> +
> +static int ltc2991_read_in(struct device *dev, u32 attr, int channel, long *val)
> +{
> +	struct ltc2991_state *st = dev_get_drvdata(dev);
> +	u32 reg;
> +
> +	switch (attr) {
> +	case hwmon_in_input:
> +		if (channel == LTC2991_VCC_CH_NR)
> +			reg = LTC2991_VCC_MSB;
> +		else
> +			reg = LTC2991_CHANNEL_V_MSB(channel - 1);
> +
> +		return ltc2991_get_voltage(st, reg, val);
> +	default:
> +		return -EOPNOTSUPP;
> +	}
> +}
> +
> +static int ltc2991_get_curr(struct ltc2991_state *st, u32 reg, int channel,
> +			    long *val)
> +{
> +	int reg_val, ret;
> +
> +	ret = ltc2991_read_reg(st, reg, 2, &reg_val);
> +	if (ret)
> +		return ret;
> +
> +	/* Vx-Vy, 19.075uV/LSB */
> +	*val = DIV_ROUND_CLOSEST(sign_extend32(reg_val, 14) * 19075, 1000)
> +				 / (st->r_sense_uohm[channel] / 1000);

If st->r_sense_uohm[channel] < 1000, the divide operation will
result in a division by zero error. Also, there is a loss of
accuracy because the sense resistor is rounded to mOhm before
being used.

> +
> +	return 0;
> +}
> +
> +static int ltc2991_read_curr(struct device *dev, u32 attr, int channel,
> +			     long *val)
> +{
> +	struct ltc2991_state *st = dev_get_drvdata(dev);
> +	u32 reg;
> +
> +	switch (attr) {
> +	case hwmon_curr_input:
> +		reg = LTC2991_CHANNEL_C_MSB(channel);
> +		return ltc2991_get_curr(st, reg, channel, val);
> +	default:
> +		return -EOPNOTSUPP;
> +	}
> +}
> +
> +static int ltc2991_get_temp(struct ltc2991_state *st, u32 reg, int channel,
> +			    long *val)
> +{
> +	int reg_val, ret;
> +
> +	ret = ltc2991_read_reg(st, reg, 2, &reg_val);
> +	if (ret)
> +		return ret;
> +
> +	/* Temp LSB = 0.0625 Degrees */
> +	*val = DIV_ROUND_CLOSEST(sign_extend32(reg_val, 12) * 1000, 16);
> +
> +	return 0;
> +}
> +
> +static int ltc2991_read_temp(struct device *dev, u32 attr, int channel,
> +			     long *val)
> +{
> +	struct ltc2991_state *st = dev_get_drvdata(dev);
> +	u32 reg;
> +
> +	switch (attr) {
> +	case hwmon_temp_input:
> +		if (channel == LTC2991_T_INT_CH_NR)
> +			reg = LTC2991_T_INT_MSB;
> +		else
> +			reg = LTC2991_CHANNEL_T_MSB(channel);
> +
> +		return ltc2991_get_temp(st, reg, channel, val);
> +	default:
> +		return -EOPNOTSUPP;
> +	}
> +}
> +
> +static int ltc2991_read(struct device *dev, enum hwmon_sensor_types type,
> +			u32 attr, int channel, long *val)
> +{
> +	switch (type) {
> +	case hwmon_in:
> +		return ltc2991_read_in(dev, attr, channel, val);
> +	case hwmon_curr:
> +		return ltc2991_read_curr(dev, attr, channel, val);
> +	case hwmon_temp:
> +		return ltc2991_read_temp(dev, attr, channel, val);
> +	default:
> +		return -EOPNOTSUPP;
> +	}
> +}
> +
> +static umode_t ltc2991_is_visible(const void *data,
> +				  enum hwmon_sensor_types type, u32 attr,
> +				  int channel)
> +{
> +	const struct ltc2991_state *st = data;
> +
> +	switch (type) {
> +	case hwmon_in:
> +		switch (attr) {
> +		case hwmon_in_input:
> +			if (channel == LTC2991_VCC_CH_NR)
> +				return 0444;
> +			if (st->temp_en[(channel - 1) / 2])
> +				break;
> +			if (channel % 2)
> +				return 0444;
> +			if (!st->r_sense_uohm[(channel - 1) / 2])
> +				return 0444;
> +		}
> +		break;
> +	case hwmon_curr:
> +		switch (attr) {
> +		case hwmon_curr_input:
> +			if (st->r_sense_uohm[channel])
> +				return 0444;
> +			break;
> +		}
> +		break;
> +	case hwmon_temp:
> +		switch (attr) {
> +		case hwmon_temp_input:
> +			if (st->temp_en[channel] ||
> +			    channel == LTC2991_T_INT_CH_NR)
> +				return 0444;
> +			break;
> +		}
> +		break;
> +	default:
> +		break;
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct hwmon_ops ltc2991_hwmon_ops = {
> +	.is_visible = ltc2991_is_visible,
> +	.read = ltc2991_read,
> +};
> +
> +static const struct hwmon_channel_info *ltc2991_info[] = {
> +	HWMON_CHANNEL_INFO(temp,
> +			   HWMON_T_INPUT,
> +			   HWMON_T_INPUT,
> +			   HWMON_T_INPUT,
> +			   HWMON_T_INPUT,
> +			   HWMON_T_INPUT
> +			   ),
> +	HWMON_CHANNEL_INFO(curr,
> +			   HWMON_C_INPUT,
> +			   HWMON_C_INPUT,
> +			   HWMON_C_INPUT,
> +			   HWMON_C_INPUT
> +			   ),
> +	HWMON_CHANNEL_INFO(in,
> +			   HWMON_I_INPUT,
> +			   HWMON_I_INPUT,
> +			   HWMON_I_INPUT,
> +			   HWMON_I_INPUT,
> +			   HWMON_I_INPUT,
> +			   HWMON_I_INPUT,
> +			   HWMON_I_INPUT,
> +			   HWMON_I_INPUT,
> +			   HWMON_I_INPUT
> +			   ),
> +	NULL
> +};
> +
> +static const struct hwmon_chip_info ltc2991_chip_info = {
> +	.ops = &ltc2991_hwmon_ops,
> +	.info = ltc2991_info,
> +};
> +
> +static const struct regmap_config ltc2991_regmap_config = {
> +	.reg_bits = 8,
> +	.val_bits = 8,
> +	.max_register = 0x1D,
> +};
> +
> +static int ltc2991_init(struct ltc2991_state *st)
> +{
> +	struct fwnode_handle *child;
> +	int ret;
> +	u32 val, addr;
> +	u8 v5_v8_reg_data = 0, v1_v4_reg_data = 0;
> +
> +	ret = devm_regulator_get_enable(&st->client->dev, "vcc");
> +	if (ret)
> +		return dev_err_probe(&st->client->dev, ret,
> +				     "failed to enable regulator\n");
> +
> +	device_for_each_child_node(&st->client->dev, child) {
> +		ret = fwnode_property_read_u32(child, "reg", &addr);
> +		if (ret < 0) {
> +			fwnode_handle_put(child);
> +			return ret;
> +		}
> +
> +		if (addr > 3) {
> +			fwnode_handle_put(child);
> +			return -EINVAL;
> +		}
> +
> +		ret = fwnode_property_read_u32(child, "shunt-resistor-micro-ohms", &val);
> +		if (!ret) {
> +			if (!val)
> +				return dev_err_probe(&st->client->dev, -EINVAL,
> +						     "shunt resistor value cannot be zero\n");
> +
> +			st->r_sense_uohm[addr] = val;
> +
> +			switch (addr) {
> +			case 0:
> +				v1_v4_reg_data |= LTC2991_V1_V2_DIFF_EN;
> +				break;
> +			case 1:
> +				v1_v4_reg_data |= LTC2991_V3_V4_DIFF_EN;
> +				break;
> +			case 2:
> +				v5_v8_reg_data |= LTC2991_V5_V6_DIFF_EN;
> +				break;
> +			case 3:
> +				v5_v8_reg_data |= LTC2991_V7_V8_DIFF_EN;
> +				break;
> +			default:
> +				break;
> +			}
> +		}
> +
> +		ret = fwnode_property_read_bool(child, "adi,temperature-enable");
> +		if (ret) {
> +			st->temp_en[addr] = ret;
> +
> +			switch (addr) {
> +			case 0:
> +				v1_v4_reg_data |= LTC2991_V1_V2_TEMP_EN;
> +				break;
> +			case 1:
> +				v1_v4_reg_data |= LTC2991_V3_V4_TEMP_EN;
> +				break;
> +			case 2:
> +				v5_v8_reg_data |= LTC2991_V5_V6_TEMP_EN;
> +				break;
> +			case 3:
> +				v5_v8_reg_data |= LTC2991_V7_V8_TEMP_EN;
> +				break;
> +			default:
> +				break;
> +			}
> +		}
> +	}
> +
> +	ret = regmap_write(st->regmap, LTC2991_V5_V8_CTRL, v5_v8_reg_data);
> +	if (ret)
> +		return dev_err_probe(&st->client->dev, ret,
> +				     "Error: Failed to set V5-V8 CTRL reg.\n");
> +
> +	ret = regmap_write(st->regmap, LTC2991_V1_V4_CTRL, v1_v4_reg_data);
> +	if (ret)
> +		return dev_err_probe(&st->client->dev, ret,
> +				     "Error: Failed to set V1-V4 CTRL reg.\n");
> +
> +	ret = regmap_write(st->regmap, LTC2991_PWM_TH_LSB_T_INT,
> +			   LTC2991_REPEAT_ACQ_EN);
> +	if (ret)
> +		return dev_err_probe(&st->client->dev, ret,
> +				     "Error: Failed to set contiuous mode.\n");
> +
> +	/* Enable all channels and trigger conversions */
> +	return regmap_write(st->regmap, LTC2991_CH_EN_TRIGGER,
> +			    LTC2991_V7_V8_EN | LTC2991_V5_V6_EN |
> +			    LTC2991_V3_V4_EN | LTC2991_V1_V2_EN |
> +			    LTC2991_T_INT_VCC_EN);
> +}
> +
> +static int ltc2991_i2c_probe(struct i2c_client *client)
> +{
> +	int ret;
> +	struct device *hwmon_dev;
> +	struct ltc2991_state *st;
> +
> +	st = devm_kzalloc(&client->dev, sizeof(*st), GFP_KERNEL);
> +	if (!st)
> +		return -ENOMEM;
> +
> +	st->client = client;
> +	st->regmap = devm_regmap_init_i2c(client, &ltc2991_regmap_config);
> +	if (IS_ERR(st->regmap))
> +		return PTR_ERR(st->regmap);
> +
> +	ret = ltc2991_init(st);
> +	if (ret)
> +		return ret;
> +
> +	hwmon_dev = devm_hwmon_device_register_with_info(&client->dev,
> +							 client->name, st,
> +							 &ltc2991_chip_info,
> +							 NULL);
> +
> +	return PTR_ERR_OR_ZERO(hwmon_dev);
> +}
> +
> +static const struct of_device_id ltc2991_of_match[] = {
> +	{ .compatible = "adi,ltc2991" },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, ltc2991_of_match);
> +
> +static const struct i2c_device_id ltc2991_i2c_id[] = {
> +	{ "ltc2991", 0 },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(i2c, ltc2991_i2c_id);
> +
> +static struct i2c_driver ltc2991_i2c_driver = {
> +	.driver = {
> +		.name = "ltc2991",
> +		.of_match_table = ltc2991_of_match,
> +	},
> +	.probe = ltc2991_i2c_probe,
> +	.id_table = ltc2991_i2c_id,
> +};
> +
> +module_i2c_driver(ltc2991_i2c_driver);
> +
> +MODULE_AUTHOR("Antoniu Miclaus <antoniu.miclaus@analog.com>");
> +MODULE_DESCRIPTION("Analog Devices LTC2991 HWMON Driver");
> +MODULE_LICENSE("GPL");