[PATCH] hwmon (ina3221) Add single-shot mode support

[Nicolin Chen <nicoleotsuka@gmail.com>]

INA3221 supports both continuous and single-shot modes. When
running in the continuous mode, it keeps measuring the inputs
and converting them to the data register even if there are no
users reading the data out. In this use case, this could be a
power waste.

So this patch adds a single-shot mode support so that ina3221
could do measurement and conversion only if users trigger it,
depending on the use case where it only needs to poll data in
a lower frequency.

The change also exposes "mode" and "available_modes" nodes to
allow users to switch between two operating modes.

Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com>
---
 Documentation/hwmon/ina3221 |   3 +
 drivers/hwmon/ina3221.c     | 109 ++++++++++++++++++++++++++++++++++++
 2 files changed, 112 insertions(+)

diff --git a/Documentation/hwmon/ina3221 b/Documentation/hwmon/ina3221
index 4b82cbfb551c..b03f4ad901ee 100644
--- a/Documentation/hwmon/ina3221
+++ b/Documentation/hwmon/ina3221
@@ -35,3 +35,6 @@ curr[123]_max           Warning alert current(mA) setting, activates the
                           average is above this value.
 curr[123]_max_alarm     Warning alert current limit exceeded
 in[456]_input           Shunt voltage(uV) for channels 1, 2, and 3 respectively
+available_modes         Available operating modes of the chip:
+                          continuous mode; single-shot mode
+mode                    Current operating mode of the chip
diff --git a/drivers/hwmon/ina3221.c b/drivers/hwmon/ina3221.c
index 17a57dbc0424..8f7da3f75d53 100644
--- a/drivers/hwmon/ina3221.c
+++ b/drivers/hwmon/ina3221.c
@@ -91,6 +91,17 @@ enum ina3221_channels {
 	INA3221_NUM_CHANNELS
 };
 
+enum ina3221_modes {
+	INA3221_MODE_SINGLE_SHOT,
+	INA3221_MODE_CONTINUOUS,
+	INA3221_NUM_MODES,
+};
+
+static const char * const ina3221_mode_names[] = {
+	[INA3221_MODE_SINGLE_SHOT] = "single-shot",
+	[INA3221_MODE_CONTINUOUS] = "continuous",
+};
+
 /**
  * struct ina3221_input - channel input source specific information
  * @label: label of channel input source
@@ -127,6 +138,11 @@ static inline bool ina3221_is_enabled(struct ina3221_data *ina, int channel)
 	       (ina->reg_config & INA3221_CONFIG_CHx_EN(channel));
 }
 
+static inline bool ina3221_is_singleshot_mode(struct ina3221_data *ina)
+{
+	return !(ina->reg_config & INA3221_CONFIG_MODE_CONTINUOUS);
+}
+
 /* Lookup table for Bus and Shunt conversion times in usec */
 static const u16 ina3221_conv_time[] = {
 	140, 204, 332, 588, 1100, 2116, 4156, 8244,
@@ -188,6 +204,11 @@ static int ina3221_read_in(struct device *dev, u32 attr, int channel, long *val)
 		if (!ina3221_is_enabled(ina, channel))
 			return -ENODATA;
 
+		/* Write CONFIG register to trigger a single-shot measurement */
+		if (ina3221_is_singleshot_mode(ina))
+			regmap_write(ina->regmap, INA3221_CONFIG,
+				     ina->reg_config);
+
 		ret = ina3221_wait_for_data(ina);
 		if (ret)
 			return ret;
@@ -232,6 +253,11 @@ static int ina3221_read_curr(struct device *dev, u32 attr,
 		if (!ina3221_is_enabled(ina, channel))
 			return -ENODATA;
 
+		/* Write CONFIG register to trigger a single-shot measurement */
+		if (ina3221_is_singleshot_mode(ina))
+			regmap_write(ina->regmap, INA3221_CONFIG,
+				     ina->reg_config);
+
 		ret = ina3221_wait_for_data(ina);
 		if (ret)
 			return ret;
@@ -532,6 +558,82 @@ static ssize_t ina3221_set_shunt(struct device *dev,
 	return count;
 }
 
+static ssize_t available_modes_show(struct device *dev,
+				    struct device_attribute *attr, char *buf)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(ina3221_mode_names); i++)
+		snprintf(buf, PAGE_SIZE, "%s%s ", buf, ina3221_mode_names[i]);
+
+	return snprintf(buf, PAGE_SIZE, "%s\n", buf);
+}
+
+static ssize_t mode_show(struct device *dev,
+			 struct device_attribute *attr, char *buf)
+{
+	struct ina3221_data *ina = dev_get_drvdata(dev);
+	int mode;
+
+	if (ina->reg_config & INA3221_CONFIG_MODE_CONTINUOUS)
+		mode = INA3221_MODE_CONTINUOUS;
+	else
+		mode = INA3221_MODE_SINGLE_SHOT;
+
+	return snprintf(buf, PAGE_SIZE, "%s\n", ina3221_mode_names[mode]);
+}
+
+static ssize_t mode_store(struct device *dev,
+			  struct device_attribute *attr,
+			  const char *buf, size_t count)
+{
+	struct ina3221_data *ina = dev_get_drvdata(dev);
+	u16 mask = INA3221_CONFIG_MODE_CONTINUOUS;
+	u16 continuous;
+	int mode, ret;
+	char name[32];
+
+	mutex_lock(&ina->lock);
+
+	snprintf(name, sizeof(name), "%s", buf);
+	strim(name);
+
+	for (mode = 0; mode < INA3221_NUM_MODES; mode++) {
+		if (!strcmp(name, ina3221_mode_names[mode]))
+			break;
+	}
+
+	switch (mode) {
+	case INA3221_MODE_SINGLE_SHOT:
+		continuous = 0;
+		break;
+	case INA3221_MODE_CONTINUOUS:
+		continuous = INA3221_CONFIG_MODE_CONTINUOUS;
+		break;
+	default:
+		mutex_unlock(&ina->lock);
+		return -EINVAL;
+	}
+
+	/* Set register to configure single-shot or continuous mode */
+	ret = regmap_update_bits(ina->regmap, INA3221_CONFIG, mask, continuous);
+	if (ret) {
+		mutex_unlock(&ina->lock);
+		return ret;
+	}
+
+	/* Cache the latest config register value */
+	ret = regmap_read(ina->regmap, INA3221_CONFIG, &ina->reg_config);
+	if (ret) {
+		mutex_unlock(&ina->lock);
+		return ret;
+	}
+
+	mutex_unlock(&ina->lock);
+
+	return count;
+}
+
 /* shunt resistance */
 static SENSOR_DEVICE_ATTR(shunt1_resistor, S_IRUGO | S_IWUSR,
 		ina3221_show_shunt, ina3221_set_shunt, INA3221_CHANNEL1);
@@ -540,10 +642,17 @@ static SENSOR_DEVICE_ATTR(shunt2_resistor, S_IRUGO | S_IWUSR,
 static SENSOR_DEVICE_ATTR(shunt3_resistor, S_IRUGO | S_IWUSR,
 		ina3221_show_shunt, ina3221_set_shunt, INA3221_CHANNEL3);
 
+/* operating mode */
+static DEVICE_ATTR_RW(mode);
+static DEVICE_ATTR_RO(available_modes);
+
 static struct attribute *ina3221_attrs[] = {
 	&sensor_dev_attr_shunt1_resistor.dev_attr.attr,
 	&sensor_dev_attr_shunt2_resistor.dev_attr.attr,
 	&sensor_dev_attr_shunt3_resistor.dev_attr.attr,
+	/* common attributes */
+	&dev_attr_mode.attr,
+	&dev_attr_available_modes.attr,
 	NULL,
 };
 ATTRIBUTE_GROUPS(ina3221);
-- 
2.17.1