[PATCH] hwmon: Add LTC2990 sensor driver

[Mike Looijmans]

This adds support for the Linear Technology LTC2990  I2C System Monitor.
The LTC2990 supports a combination of voltage, current and temperature
monitoring, but this driver currently only supports reading two currents
by measuring two differential voltages across series resistors.

This is sufficient to support the Topic Miami SOM which uses this chip
to monitor the currents flowing into the FPGA and the CPU parts.

Signed-off-by: Mike Looijmans <mike.looijmans@xxxxxxxx>
---
 drivers/hwmon/Kconfig   |  15 +++
 drivers/hwmon/Makefile  |   1 +
 drivers/hwmon/ltc2990.c | 273 ++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 289 insertions(+)
 create mode 100644 drivers/hwmon/ltc2990.c

diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 80a73bf..b3eef31 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -685,6 +685,21 @@ config SENSORS_LTC2945
 	  This driver can also be built as a module. If so, the module will
 	  be called ltc2945.
 
+config SENSORS_LTC2990
+	tristate "Linear Technology LTC2990 (current monitoring mode only)"
+	depends on I2C
+	select REGMAP_I2C
+	default n
+	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 this driver currently only
+	  supports reading two currents by measuring two differential voltages
+	  across series resistors.
+
+	  This driver can also be built as a module. If so, the module will
+	  be called ltc2990.
+
 config SENSORS_LTC4151
 	tristate "Linear Technology LTC4151"
 	depends on I2C
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index 12a3239..e4bd15b 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -101,6 +101,7 @@ obj-$(CONFIG_SENSORS_LM95234)	+= lm95234.o
 obj-$(CONFIG_SENSORS_LM95241)	+= lm95241.o
 obj-$(CONFIG_SENSORS_LM95245)	+= lm95245.o
 obj-$(CONFIG_SENSORS_LTC2945)	+= ltc2945.o
+obj-$(CONFIG_SENSORS_LTC2990)	+= ltc2990.o
 obj-$(CONFIG_SENSORS_LTC4151)	+= ltc4151.o
 obj-$(CONFIG_SENSORS_LTC4215)	+= ltc4215.o
 obj-$(CONFIG_SENSORS_LTC4222)	+= ltc4222.o
diff --git a/drivers/hwmon/ltc2990.c b/drivers/hwmon/ltc2990.c
new file mode 100644
index 0000000..161d995
--- /dev/null
+++ b/drivers/hwmon/ltc2990.c
@@ -0,0 +1,273 @@
+/*
+ * driver for Linear Technology LTC2990 power monitor
+ *
+ * Copyright (C) 2014 Topic Embedded Products
+ * Author: Mike Looijmans <mike.looijmans@xxxxxxxx>
+ *
+ * License: GPLv2
+ *
+ * This driver assumes the chip is wired as a dual current monitor, and
+ * reports the voltage drop across two series resistors.
+ */
+
+#include <linux/bug.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/i2c.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+
+#define LTC2990_STATUS	0x00
+#define LTC2990_CONTROL	0x01
+#define LTC2990_TRIGGER	0x02
+#define LTC2990_TINT_MSB	0x04
+#define LTC2990_TINT_LSB	0x05
+#define LTC2990_V1_MSB	0x06
+#define LTC2990_V1_LSB	0x07
+#define LTC2990_V2_MSB	0x08
+#define LTC2990_V2_LSB	0x09
+#define LTC2990_V3_MSB	0x0A
+#define LTC2990_V3_LSB	0x0B
+#define LTC2990_V4_MSB	0x0C
+#define LTC2990_V4_LSB	0x0D
+#define LTC2990_VCC_MSB	0x0E
+#define LTC2990_VCC_LSB	0x0F
+
+#define LTC2990_STATUS_BUSY	BIT(0)
+#define LTC2990_STATUS_TINT	BIT(1)
+#define LTC2990_STATUS_V1	BIT(2)
+#define LTC2990_STATUS_V2	BIT(3)
+#define LTC2990_STATUS_V3	BIT(4)
+#define LTC2990_STATUS_V4	BIT(5)
+#define LTC2990_STATUS_VCC	BIT(6)
+
+/* Only define control settings we actually use */
+#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
+
+struct ltc2990_data {
+	struct device *hwmon_dev;
+	struct mutex update_lock;
+	unsigned long last_updated;
+	short values[6];
+	bool valid;
+	u8 update_counter;
+};
+
+static int ltc2990_write(struct i2c_client *i2c, u8 reg, u8 value)
+{
+	return i2c_smbus_write_byte_data(i2c, reg, value);
+}
+
+static int ltc2990_read_byte(struct i2c_client *i2c, u8 reg)
+{
+	return i2c_smbus_read_byte_data(i2c, reg);
+}
+
+static int ltc2990_read_word(struct i2c_client *i2c, u8 reg)
+{
+	int result = i2c_smbus_read_word_data(i2c, reg);
+	/* Result is MSB first, but smbus specs say LSB first, so swap the
+	 * result */
+	return result < 0 ? result : swab16(result);
+}
+
+static struct ltc2990_data *ltc2990_update_device(struct device *dev)
+{
+	struct i2c_client *i2c = to_i2c_client(dev);
+	struct ltc2990_data *data = i2c_get_clientdata(i2c);
+	struct ltc2990_data *ret = data;
+	unsigned int timeout;
+
+	mutex_lock(&data->update_lock);
+
+	/* Update about 4 times per second max */
+	if (time_after(jiffies, data->last_updated + HZ / 4) || !data->valid) {
+		int val;
+		int i;
+
+		/* Trigger ADC, any value will do */
+		val = ltc2990_write(i2c, LTC2990_TRIGGER, 1);
+		if (unlikely(val < 0)) {
+			ret = ERR_PTR(val);
+			goto abort;
+		}
+
+		/* Wait for conversion complete */
+		timeout = 200;
+		for (;;) {
+			usleep_range(2000, 4000);
+			val = ltc2990_read_byte(i2c, LTC2990_STATUS);
+			if (unlikely(val < 0)) {
+				ret = ERR_PTR(val);
+				goto abort;
+			}
+			/* Single-shot mode, wait for conversion to complete */
+			if ((val & LTC2990_STATUS_BUSY) == 0)
+				break;
+			if (--timeout == 0) {
+				ret = ERR_PTR(-ETIMEDOUT);
+				goto abort;
+			}
+		}
+
+		/* Read all registers */
+		for (i = 0; i < ARRAY_SIZE(data->values); ++i) {
+			val = ltc2990_read_word(i2c, (i<<1) + LTC2990_TINT_MSB);
+			if (unlikely(val < 0)) {
+				dev_dbg(dev,
+					"Failed to read ADC value: error %d\n",
+					val);
+				ret = ERR_PTR(val);
+				goto abort;
+			}
+			data->values[i] = val & 0x7FFF; /* Strip 'new' bit */
+		}
+		data->last_updated = jiffies;
+		data->valid = 1;
+
+		/*
+		 *  Quirk: Second trigger is ignored? After this, the BUSY will
+		 * still be set to "0" and no conversion performed.
+		 */
+		val = ltc2990_write(i2c, LTC2990_TRIGGER, 0);
+	}
+abort:
+	mutex_unlock(&data->update_lock);
+	return ret;
+}
+
+/* Return the converted value from the given register in uV or mC */
+static int ltc2990_get_value(struct ltc2990_data *data, u8 index)
+{
+	s32 result;
+	s16 v;
+
+	if (index == 0) { /* internal temp, 0.0625 degrees/LSB, 12-bit  */
+		v = data->values[index] << 3;
+		result = (s32)v * 1000 >> 7;
+	} else if (index < 5) { /* Vx-Vy, 19.42uV/LSB, 14-bit */
+		v = data->values[index] << 2;
+		result = (s32)v * 1942 / (4 * 100);
+	} else { /* Vcc, 305.18ÎV/LSB, 2.5V offset, 14-bit */
+		v = data->values[index] << 2;
+		result = (s32)v * 30518 / (4 * 100);
+		result += 2500000;
+	}
+	return result;
+}
+
+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 = ltc2990_update_device(dev);
+	int value;
+
+	if (IS_ERR(data))
+		return PTR_ERR(data);
+
+	value = ltc2990_get_value(data, attr->index);
+	return snprintf(buf, PAGE_SIZE, "%d\n", value);
+}
+
+static SENSOR_DEVICE_ATTR(temp_int, S_IRUGO, ltc2990_show_value, NULL, 0);
+static SENSOR_DEVICE_ATTR(v1v2_diff, S_IRUGO, ltc2990_show_value, NULL, 1);
+static SENSOR_DEVICE_ATTR(v3v4_diff, S_IRUGO, ltc2990_show_value, NULL, 3);
+static SENSOR_DEVICE_ATTR(vcc, S_IRUGO, ltc2990_show_value, NULL, 5);
+
+static struct attribute *ltc2990_attributes[] = {
+	&sensor_dev_attr_temp_int.dev_attr.attr,
+	&sensor_dev_attr_v1v2_diff.dev_attr.attr,
+	&sensor_dev_attr_v3v4_diff.dev_attr.attr,
+	&sensor_dev_attr_vcc.dev_attr.attr,
+	NULL,
+};
+
+static const struct attribute_group ltc2990_group = {
+	.attrs = ltc2990_attributes,
+};
+
+static int ltc2990_i2c_probe(
+	struct i2c_client *i2c, const struct i2c_device_id *id)
+{
+	int ret;
+	struct ltc2990_data *ltc2990;
+
+	if (!i2c_check_functionality(i2c->adapter, I2C_FUNC_SMBUS_BYTE_DATA))
+		return -ENODEV;
+
+	ltc2990 = devm_kzalloc(&i2c->dev,
+		sizeof(struct ltc2990_data), GFP_KERNEL);
+	if (ltc2990 == NULL)
+		return -ENOMEM;
+
+	ret = ltc2990_read_byte(i2c, 0);
+	if (ret < 0) {
+		dev_err(&i2c->dev, "Could not read LTC2990 on i2c bus.\n");
+		return ret;
+	}
+	ret = ltc2990_write(i2c, LTC2990_CONTROL,
+		LTC2990_CONTROL_SINGLE | LTC2990_CONTROL_MEASURE_ALL |
+		LTC2990_CONTROL_MODE_CURRENT);
+	if (ret < 0) {
+		dev_err(&i2c->dev, "Error: Failed to set control mode.\n");
+		return ret;
+	}
+
+	mutex_init(&ltc2990->update_lock);
+	i2c_set_clientdata(i2c, ltc2990);
+
+	/* Register sysfs hooks */
+	ret = sysfs_create_group(&i2c->dev.kobj, &ltc2990_group);
+	if (ret)
+		return ret;
+
+	ltc2990->hwmon_dev = hwmon_device_register(&i2c->dev);
+	if (IS_ERR(ltc2990->hwmon_dev)) {
+		ret = PTR_ERR(ltc2990->hwmon_dev);
+		goto out_hwmon_device_register;
+	}
+
+	return 0;
+
+out_hwmon_device_register:
+	sysfs_remove_group(&i2c->dev.kobj, &ltc2990_group);
+	return ret;
+}
+
+static int ltc2990_i2c_remove(struct i2c_client *i2c)
+{
+	struct ltc2990_data *ltc2990 = i2c_get_clientdata(i2c);
+
+	hwmon_device_unregister(ltc2990->hwmon_dev);
+	sysfs_remove_group(&i2c->dev.kobj, &ltc2990_group);
+	return 0;
+}
+
+static const struct i2c_device_id ltc2990_i2c_id[] = {
+	{ "ltc2990", 0 },
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, ltc2990_i2c_id);
+
+static struct i2c_driver ltc2990_i2c_driver = {
+	.driver = {
+		.name = "ltc2990",
+	},
+	.probe    = ltc2990_i2c_probe,
+	.remove   = ltc2990_i2c_remove,
+	.id_table = ltc2990_i2c_id,
+};
+
+module_i2c_driver(ltc2990_i2c_driver);
+
+MODULE_DESCRIPTION("LTC2990 Sensor Driver");
+MODULE_AUTHOR("Topic Embedded Products");
+MODULE_LICENSE("GPL v2");
-- 
1.9.1

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