Re: [PATCH v2 3/3] hwmon: ltc2990: support all measurement modes

[Guenter Roeck <linux@roeck-us.net>]

On 11/17/2016 04:10 AM, Tom Levens wrote:
> Updated version of the ltc2990 driver which supports all measurement
> modes available in the chip. The mode can be set through a devicetree
> attribute.

property

>
> Signed-off-by: Tom Levens <tom.levens@cern.ch>
> ---
>
> Changes since v1:
>   * Refactored value conversion (patch 1/3)
>   * Split the devicetree binding into separate patch (patch 2/3)
>   * Specifying an invalid mode now returns -EINVAL, previously this
>     only issued a warning and used the default value
>   * Removed the "mode" sysfs attribute, as the mode of the chip is
>     hardware specific and should not be user configurable. This allows much
>     simpler code as a result.
>
>  Documentation/hwmon/ltc2990 |   24 ++++---
>  drivers/hwmon/Kconfig       |    7 +--
>  drivers/hwmon/ltc2990.c     |  167 ++++++++++++++++++++++++++++++++++++-------
>  3 files changed, 159 insertions(+), 39 deletions(-)
>
> diff --git a/Documentation/hwmon/ltc2990 b/Documentation/hwmon/ltc2990
> index c25211e..3ed68f6 100644
> --- a/Documentation/hwmon/ltc2990
> +++ b/Documentation/hwmon/ltc2990
> @@ -8,6 +8,7 @@ Supported chips:
>      Datasheet: http://www.linear.com/product/ltc2990
>
>  Author: Mike Looijmans <mike.looijmans@topic.nl>
> +        Tom Levens <tom.levens@cern.ch>
>
>
>  Description
> @@ -16,10 +17,8 @@ Description
>  LTC2990 is a Quad I2C Voltage, Current and Temperature Monitor.
>  The chip's inputs can measure 4 voltages, or two inputs together (1+2 and 3+4)
>  can be combined to measure a differential voltage, which is typically used to
> -measure current through a series resistor, or a temperature.
> -
> -This driver currently uses the 2x differential mode only. In order to support
> -other modes, the driver will need to be expanded.
> +measure current through a series resistor, or a temperature with an external
> +diode.
>
>
>  Usage Notes
> @@ -32,12 +31,19 @@ devices explicitly.
>  Sysfs attributes
>  ----------------
>
> +in0_input     Voltage at Vcc pin in millivolt (range 2.5V to 5V)
> +temp1_input   Internal chip temperature in millidegrees Celcius
> +
> +A subset of the following attributes are visible, depending on the measurement
> +mode of the chip.
> +
> +in[1-4]_input Voltage at V[1-4] pin in millivolt
> +temp2_input   External temperature sensor TR1 in millidegrees Celcius
> +temp3_input   External temperature sensor TR2 in millidegrees Celcius
> +curr1_input   Current in mA across V1-V2 assuming a 1mOhm sense resistor
> +curr2_input   Current in mA across V3-V4 assuming a 1mOhm sense resistor
> +
>  The "curr*_input" measurements actually report the voltage drop across the
>  input pins in microvolts. This is equivalent to the current through a 1mOhm
>  sense resistor. Divide the reported value by the actual sense resistor value
>  in mOhm to get the actual value.
> -
> -in0_input     Voltage at Vcc pin in millivolt (range 2.5V to 5V)
> -temp1_input   Internal chip temperature in millidegrees Celcius
> -curr1_input   Current in mA across v1-v2 assuming a 1mOhm sense resistor.
> -curr2_input   Current in mA across v3-v4 assuming a 1mOhm sense resistor.
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index 45cef3d..f7096ca 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -699,15 +699,12 @@ config SENSORS_LTC2945
>  	  be called ltc2945.
>
>  config SENSORS_LTC2990
> -	tristate "Linear Technology LTC2990 (current monitoring mode only)"
> +	tristate "Linear Technology LTC2990"
>  	depends on I2C
>  	help
>  	  If you say yes here you get support for Linear Technology LTC2990
>  	  I2C System Monitor. The LTC2990 supports a combination of voltage,
> -	  current and temperature monitoring, but in addition to the Vcc supply
> -	  voltage and chip temperature, this driver currently only supports
> -	  reading two currents by measuring two differential voltages across
> -	  series resistors.
> +	  current and temperature monitoring.
>
>  	  This driver can also be built as a module. If so, the module will
>  	  be called ltc2990.
> diff --git a/drivers/hwmon/ltc2990.c b/drivers/hwmon/ltc2990.c
> index 0ec4102..e8d36f5 100644
> --- a/drivers/hwmon/ltc2990.c
> +++ b/drivers/hwmon/ltc2990.c
> @@ -6,11 +6,7 @@
>   *
>   * License: GPLv2
>   *
> - * This driver assumes the chip is wired as a dual current monitor, and
> - * reports the voltage drop across two series resistors. It also reports
> - * the chip's internal temperature and Vcc power supply voltage.
> - *
> - * Value conversion refactored
> + * Value conversion refactored and support for all measurement modes added
>   * by Tom Levens <tom.levens@cern.ch>
>   */
>
> @@ -21,6 +17,7 @@
>  #include <linux/i2c.h>
>  #include <linux/kernel.h>
>  #include <linux/module.h>
> +#include <linux/of.h>
>
>  #define LTC2990_STATUS	0x00
>  #define LTC2990_CONTROL	0x01
> @@ -35,32 +32,96 @@
>  #define LTC2990_CONTROL_KELVIN		BIT(7)
>  #define LTC2990_CONTROL_SINGLE		BIT(6)
>  #define LTC2990_CONTROL_MEASURE_ALL	(0x3 << 3)
> -#define LTC2990_CONTROL_MODE_CURRENT	0x06
> -#define LTC2990_CONTROL_MODE_VOLTAGE	0x07
> +#define LTC2990_CONTROL_MODE_DEFAULT	0x06

I think LTC2990_CONTROL_MODE_CURRENT was better - it describes the actual mode.
Changing the define to _DEFAULT does not really improve code readability.

> +#define LTC2990_CONTROL_MODE_MAX	0x07
> +
> +#define LTC2990_IN0	BIT(0)
> +#define LTC2990_IN1	BIT(1)
> +#define LTC2990_IN2	BIT(2)
> +#define LTC2990_IN3	BIT(3)
> +#define LTC2990_IN4	BIT(4)
> +#define LTC2990_CURR1	BIT(5)
> +#define LTC2990_CURR2	BIT(6)
> +#define LTC2990_TEMP1	BIT(7)
> +#define LTC2990_TEMP2	BIT(8)
> +#define LTC2990_TEMP3	BIT(9)
> +
> +static const int ltc2990_attrs_ena[] = {
> +	LTC2990_IN1 | LTC2990_IN2 | LTC2990_TEMP3,
> +	LTC2990_CURR1 | LTC2990_TEMP3,
> +	LTC2990_CURR1 | LTC2990_IN3 | LTC2990_IN4,
> +	LTC2990_TEMP2 | LTC2990_IN3 | LTC2990_IN4,
> +	LTC2990_TEMP2 | LTC2990_CURR2,
> +	LTC2990_TEMP2 | LTC2990_TEMP3,
> +	LTC2990_CURR1 | LTC2990_CURR2,
> +	LTC2990_IN1 | LTC2990_IN2 | LTC2990_IN3 | LTC2990_IN4
> +};
> +
> +struct ltc2990_data {
> +	struct i2c_client *i2c;
> +	u32 mode;
> +};
>
>  /* Return the converted value from the given register in uV or mC */
> -static int ltc2990_get_value(struct i2c_client *i2c, u8 reg, s32 *result)
> +static int ltc2990_get_value(struct i2c_client *i2c, int index, s32 *result)
>  {
>  	s32 val;
> +	u8 reg;
> +
> +	switch (index) {
> +	case LTC2990_IN0:
> +		reg = LTC2990_VCC_MSB;
> +		break;
> +	case LTC2990_IN1:
> +	case LTC2990_CURR1:
> +	case LTC2990_TEMP2:
> +		reg = LTC2990_V1_MSB;
> +		break;
> +	case LTC2990_IN2:
> +		reg = LTC2990_V2_MSB;
> +		break;
> +	case LTC2990_IN3:
> +	case LTC2990_CURR2:
> +	case LTC2990_TEMP3:
> +		reg = LTC2990_V3_MSB;
> +		break;
> +	case LTC2990_IN4:
> +		reg = LTC2990_V4_MSB;
> +		break;
> +	case LTC2990_TEMP1:
> +		reg = LTC2990_TINT_MSB;
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
>
>  	val = i2c_smbus_read_word_swapped(i2c, reg);
>  	if (unlikely(val < 0))
>  		return val;
>
> -	switch (reg) {
> -	case LTC2990_TINT_MSB:
> -		/* internal temp, 0.0625 degrees/LSB, 13-bit  */
> +	switch (index) {
> +	case LTC2990_TEMP1:
> +	case LTC2990_TEMP2:
> +	case LTC2990_TEMP3:
> +		/* temp, 0.0625 degrees/LSB, 13-bit  */
>  		*result = sign_extend32(val, 12) * 1000 / 16;
>  		break;
> -	case LTC2990_V1_MSB:
> -	case LTC2990_V3_MSB:
> -		 /* Vx-Vy, 19.42uV/LSB. Depends on mode. */
> +	case LTC2990_CURR1:
> +	case LTC2990_CURR2:
> +		 /* Vx-Vy, 19.42uV/LSB */
>  		*result = sign_extend32(val, 14) * 1942 / 100;
>  		break;
> -	case LTC2990_VCC_MSB:
> -		/* Vcc, 305.18μV/LSB, 2.5V offset */
> +	case LTC2990_IN0:
> +		/* Vcc, 305.18uV/LSB, 2.5V offset */
>  		*result = sign_extend32(val, 14) * 30518 / (100 * 1000) + 2500;
>  		break;
> +	case LTC2990_IN1:
> +	case LTC2990_IN2:
> +	case LTC2990_IN3:
> +	case LTC2990_IN4:
> +		/* Vx: 305.18uV/LSB */
> +		*result = sign_extend32(val, 14) * 30518 / (100 * 1000);
> +		break;
>  	default:
>  		return -EINVAL; /* won't happen, keep compiler happy */
>  	}
> @@ -72,48 +133,104 @@ static ssize_t ltc2990_show_value(struct device *dev,
>  				  struct device_attribute *da, char *buf)
>  {
>  	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
> +	struct ltc2990_data *data = dev_get_drvdata(dev);
>  	s32 value;
>  	int ret;
>
> -	ret = ltc2990_get_value(dev_get_drvdata(dev), attr->index, &value);
> +	ret = ltc2990_get_value(data->i2c, attr->index, &value);
>  	if (unlikely(ret < 0))
>  		return ret;
>
>  	return snprintf(buf, PAGE_SIZE, "%d\n", value);
>  }
>
> +static umode_t ltc2990_attrs_visible(struct kobject *kobj,
> +				     struct attribute *a, int n)
> +{
> +	struct device *dev = container_of(kobj, struct device, kobj);
> +	struct ltc2990_data *data = dev_get_drvdata(dev);
> +	struct device_attribute *da =
> +			container_of(a, struct device_attribute, attr);
> +	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
> +
> +	if (attr->index == LTC2990_TEMP1 ||
> +	    attr->index == LTC2990_IN0 ||
> +	    attr->index & ltc2990_attrs_ena[data->mode])
> +		return a->mode;
> +	else

Unnecessary else

> +		return 0;
> +}
> +
>  static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, ltc2990_show_value, NULL,
> -			  LTC2990_TINT_MSB);
> +			  LTC2990_TEMP1);
> +static SENSOR_DEVICE_ATTR(temp2_input, S_IRUGO, ltc2990_show_value, NULL,
> +			  LTC2990_TEMP2);
> +static SENSOR_DEVICE_ATTR(temp3_input, S_IRUGO, ltc2990_show_value, NULL,
> +			  LTC2990_TEMP3);
>  static SENSOR_DEVICE_ATTR(curr1_input, S_IRUGO, ltc2990_show_value, NULL,
> -			  LTC2990_V1_MSB);
> +			  LTC2990_CURR1);
>  static SENSOR_DEVICE_ATTR(curr2_input, S_IRUGO, ltc2990_show_value, NULL,
> -			  LTC2990_V3_MSB);
> +			  LTC2990_CURR2);
>  static SENSOR_DEVICE_ATTR(in0_input, S_IRUGO, ltc2990_show_value, NULL,
> -			  LTC2990_VCC_MSB);
> +			  LTC2990_IN0);
> +static SENSOR_DEVICE_ATTR(in1_input, S_IRUGO, ltc2990_show_value, NULL,
> +			  LTC2990_IN1);
> +static SENSOR_DEVICE_ATTR(in2_input, S_IRUGO, ltc2990_show_value, NULL,
> +			  LTC2990_IN2);
> +static SENSOR_DEVICE_ATTR(in3_input, S_IRUGO, ltc2990_show_value, NULL,
> +			  LTC2990_IN3);
> +static SENSOR_DEVICE_ATTR(in4_input, S_IRUGO, ltc2990_show_value, NULL,
> +			  LTC2990_IN4);
>
>  static struct attribute *ltc2990_attrs[] = {
>  	&sensor_dev_attr_temp1_input.dev_attr.attr,
> +	&sensor_dev_attr_temp2_input.dev_attr.attr,
> +	&sensor_dev_attr_temp3_input.dev_attr.attr,
>  	&sensor_dev_attr_curr1_input.dev_attr.attr,
>  	&sensor_dev_attr_curr2_input.dev_attr.attr,
>  	&sensor_dev_attr_in0_input.dev_attr.attr,
> +	&sensor_dev_attr_in1_input.dev_attr.attr,
> +	&sensor_dev_attr_in2_input.dev_attr.attr,
> +	&sensor_dev_attr_in3_input.dev_attr.attr,
> +	&sensor_dev_attr_in4_input.dev_attr.attr,
>  	NULL,
>  };
> -ATTRIBUTE_GROUPS(ltc2990);
> +
> +static const struct attribute_group ltc2990_group = {
> +	.attrs = ltc2990_attrs,
> +	.is_visible = ltc2990_attrs_visible,
> +};
> +__ATTRIBUTE_GROUPS(ltc2990);
>
>  static int ltc2990_i2c_probe(struct i2c_client *i2c,
>  			     const struct i2c_device_id *id)
>  {
>  	int ret;
>  	struct device *hwmon_dev;
> +	struct ltc2990_data *data;
> +	struct device_node *of_node = i2c->dev.of_node;
>
>  	if (!i2c_check_functionality(i2c->adapter, I2C_FUNC_SMBUS_BYTE_DATA |
>  				     I2C_FUNC_SMBUS_WORD_DATA))
>  		return -ENODEV;
>
> -	/* Setup continuous mode, current monitor */
> +	data = devm_kzalloc(&i2c->dev, sizeof(struct ltc2990_data), GFP_KERNEL);
> +	if (unlikely(!data))
> +		return -ENOMEM;
> +	data->i2c = i2c;
> +
> +	if (!of_node || of_property_read_u32(of_node, "lltc,mode", &data->mode))
> +		data->mode = LTC2990_CONTROL_MODE_DEFAULT;

Iam arguing with myself if we should still do this or if we should read the mode
from the chip instead if it isn't provided (after all, it may have been initialized
by the BIOS/ROMMON).

Mike, would that break your application, or can you specify the mode in devicetree ?

Thanks,
Guenter

> +
> +	if (data->mode > LTC2990_CONTROL_MODE_MAX) {
> +		dev_err(&i2c->dev, "Error: Invalid mode %d.\n", data->mode);
> +		return -EINVAL;
> +	}
> +
> +	/* Setup continuous mode */
>  	ret = i2c_smbus_write_byte_data(i2c, LTC2990_CONTROL,
>  					LTC2990_CONTROL_MEASURE_ALL |
> -					LTC2990_CONTROL_MODE_CURRENT);
> +					data->mode);
>  	if (ret < 0) {
>  		dev_err(&i2c->dev, "Error: Failed to set control mode.\n");
>  		return ret;
> @@ -127,7 +244,7 @@ static int ltc2990_i2c_probe(struct i2c_client *i2c,
>
>  	hwmon_dev = devm_hwmon_device_register_with_groups(&i2c->dev,
>  							   i2c->name,
> -							   i2c,
> +							   data,
>  							   ltc2990_groups);
>
>  	return PTR_ERR_OR_ZERO(hwmon_dev);
>