[PATCH v8 0/2] Add an initial DT binding doc for ina3221

[PATCH v8 0/2] Add an initial DT binding doc for ina3221

[Nicolin Chen]

This series adds a initial DT binding doc for ina3221. It defines
a child node to describe the input source of each ina3221 channel.
Then it changes the driver to handle the information properly.

Changelog
v7->v8:
 * Refined two places in ina3221 driver (PATCH-2)
v6->v7:
 * Refined the example in the binding doc (PATCH-1)
v5->v6:
 * Removed status property and merged examples (PATCH-1)
 * Added in[123]_enable sysfs nodes (PATCH-2)
v4->v5:
 * Changed two property names of child node (PATCH-1)
 * Changed the driver accordingly and simplified is_visible (PATCH-2)
v3->v4:
 * Fixed one place in child DT node bindings (PATCH-1)
 * Changed the driver accordingly and added is_visible (PATCH-2)
v2->v3:
 * Fixed two places in DT bindings (PATCH-1)
v1->v2:
 * Redefined DT bindings (detail in PATCH-1)
 * Changed the driver code accordingly (detail in PATCH-2)

Nicolin Chen (2):
  dt-bindings: hwmon: Add ina3221 documentation
  hwmon: ina3221: Read channel input source info from DT

 .../devicetree/bindings/hwmon/ina3221.txt     |  44 ++++
 Documentation/hwmon/ina3221                   |   2 +
 drivers/hwmon/ina3221.c                       | 234 ++++++++++++++++--
 3 files changed, 266 insertions(+), 14 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/hwmon/ina3221.txt

-- 
2.17.1

[PATCH v8 1/2] dt-bindings: hwmon: Add ina3221 documentation

[Nicolin Chen]

Texas Instruments INA3221 is a triple-channel shunt and bus
voltage monitor. This patch adds a DT binding doc for it.

Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com>
---
Changelog
v7->v8:
 * N/A
v6->v7:
 * Restored three channel examples and merged them with the parent one
v5->v6:
 * Removed status property as no need to explicitly list it.
 * Combined all examples into a complete one.
v4->v5:
 * Replaced "input-id" with "reg" and added address-cells and size-cells
 * Replaced "input-label" with "label"
 * Replaced "shunt-resistor" with "shunt-resistor-micro-ohms"
v3->v4:
 * Removed the attempt of putting labels in the node names
 * Added a new optional label property in the child node
 * Updated examples accordingly
v2->v3:
 * Added a simple subject in the line 1
 * Fixed the shunt resistor value in the example
v1->v2:
 * Dropped channel name properties
 * Added child node definitions.
 * * Added shunt resistor property in the child node
 * * Added status property to indicate connection status
 * * Changed to use child node name as the label of input source

 .../devicetree/bindings/hwmon/ina3221.txt     | 44 +++++++++++++++++++
 1 file changed, 44 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/hwmon/ina3221.txt

diff --git a/Documentation/devicetree/bindings/hwmon/ina3221.txt b/Documentation/devicetree/bindings/hwmon/ina3221.txt
new file mode 100644
index 000000000000..a7b25caa2b8e
--- /dev/null
+++ b/Documentation/devicetree/bindings/hwmon/ina3221.txt
@@ -0,0 +1,44 @@
+Texas Instruments INA3221 Device Tree Bindings
+
+1) ina3221 node
+  Required properties:
+  - compatible: Must be "ti,ina3221"
+  - reg: I2C address
+
+  Optional properties:
+  = The node contains optional child nodes for three channels =
+  = Each child node describes the information of input source =
+
+  - #address-cells: Required only if a child node is present. Must be 1.
+  - #size-cells: Required only if a child node is present. Must be 0.
+
+2) child nodes
+  Required properties:
+  - reg: Must be 0, 1 or 2, corresponding to IN1, IN2 or IN3 port of INA3221
+
+  Optional properties:
+  - label: Name of the input source
+  - shunt-resistor-micro-ohms: Shunt resistor value in micro-Ohm
+
+Example:
+
+ina3221@40 {
+	compatible = "ti,ina3221";
+	reg = <0x40>;
+	#address-cells = <1>;
+	#size-cells = <0>;
+
+	input@0 {
+		reg = <0x0>;
+		status = "disabled";
+	};
+	input@1 {
+		reg = <0x1>;
+		shunt-resistor-micro-ohms = <5000>;
+	};
+	input@2 {
+		reg = <0x2>;
+		label = "VDD_5V";
+		shunt-resistor-micro-ohms = <5000>;
+	};
+};
-- 
2.17.1

[PATCH v8 2/2] hwmon: ina3221: Read channel input source info from DT

[Nicolin Chen]

An ina3221 chip has three input ports. Each port is used
to measure the voltage and current of its input source.

The DT binding now has defined bindings for their input
sources, so the driver should read these information and
handle accordingly.

This patch adds a new structure of input source specific
information including input source label, shunt resistor
value and its connection status. It exposes these labels
via in[123]_label sysfs nodes upon available, and also
disables those channels where there are no input source
being connected. Meanwhile, it also adds in[123]_enable
sysfs nodes for users to get control of three channels,
and returns -ENODATA code for any sensor read according
to hwmon ABI.

Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com>
---
Changelog
v7->v8:
 * Rebased the change after the new suspend-resume patch
 * * Please apply suspend-resume patch prior to this one
 * Renamed ina3221_is_enable() to ina3221_is_enabled()
 * Removed "> 0" check in the is_enabled() function
 * Replaced regmap_read() with ina->reg_config in is_enabled()
 * Used kstrtobool() in the ina3221_set_enable() function
v6->v7:
 * N/A
v5->v6:
 * Removed the code of hiding disconnected channels
 * Added in[123]_label sysfs nodes to control channels
 * Added -ENODATA return for sensor read at disabled channels
v4->v5:
 * Replaced "shunt-resistor" with "shunt-resistor-micro-ohms"
 * Replaced "input-label" with "label"
 * Replaced "input-id" with "reg"
 * Simplified is_visible() by using index of the attr
 * Moved inX_label to index-0 and added comments for safety
v3->v4:
 * Added is_visible callback function to hide sysfs nodes
v2->v3:
 * N/A
v1->v2:
 * Added a structure for input source corresponding to DT bindings
 * Moved shunt resistor value to the structure
 * Defined in[123]_label sysfs nodes instead of name[123]_input
 * Updated probe() function to get information from DT
 * Updated ina3221 hwmon documentation for the labels
 * Dropped dynamical group definition to keep all groups as they were

 Documentation/hwmon/ina3221 |   2 +
 drivers/hwmon/ina3221.c     | 234 +++++++++++++++++++++++++++++++++---
 2 files changed, 222 insertions(+), 14 deletions(-)

diff --git a/Documentation/hwmon/ina3221 b/Documentation/hwmon/ina3221
index 0ff74854cb2e..4b82cbfb551c 100644
--- a/Documentation/hwmon/ina3221
+++ b/Documentation/hwmon/ina3221
@@ -21,6 +21,8 @@ and power are calculated host-side from these.
 Sysfs entries
 -------------
 
+in[123]_label           Voltage channel labels
+in[123]_enable          Voltage channel enable controls
 in[123]_input           Bus voltage(mV) channels
 curr[123]_input         Current(mA) measurement channels
 shunt[123]_resistor     Shunt resistance(uOhm) channels
diff --git a/drivers/hwmon/ina3221.c b/drivers/hwmon/ina3221.c
index 26f66f728b27..f7eaa58f295e 100644
--- a/drivers/hwmon/ina3221.c
+++ b/drivers/hwmon/ina3221.c
@@ -41,6 +41,7 @@
 #define INA3221_CONFIG_MODE_SHUNT	BIT(1)
 #define INA3221_CONFIG_MODE_BUS		BIT(2)
 #define INA3221_CONFIG_MODE_CONTINUOUS	BIT(3)
+#define INA3221_CONFIG_CHx_EN(x)	BIT(14 - (x))
 
 #define INA3221_RSHUNT_DEFAULT		10000
 
@@ -75,6 +76,9 @@ enum ina3221_channels {
 };
 
 static const unsigned int register_channel[] = {
+	[INA3221_BUS1] = INA3221_CHANNEL1,
+	[INA3221_BUS2] = INA3221_CHANNEL2,
+	[INA3221_BUS3] = INA3221_CHANNEL3,
 	[INA3221_SHUNT1] = INA3221_CHANNEL1,
 	[INA3221_SHUNT2] = INA3221_CHANNEL2,
 	[INA3221_SHUNT3] = INA3221_CHANNEL3,
@@ -86,20 +90,88 @@ static const unsigned int register_channel[] = {
 	[INA3221_WARN3] = INA3221_CHANNEL3,
 };
 
+/**
+ * struct ina3221_input - channel input source specific information
+ * @label: label of channel input source
+ * @shunt_resistor: shunt resistor value of channel input source
+ * @disconnected: connection status of channel input source
+ */
+struct ina3221_input {
+	const char *label;
+	int shunt_resistor;
+	bool disconnected;
+};
+
 /**
  * struct ina3221_data - device specific information
  * @regmap: Register map of the device
  * @fields: Register fields of the device
- * @shunt_resistors: Array of resistor values per channel
+ * @inputs: Array of channel input source specific structures
  * @reg_config: Register value of INA3221_CONFIG
  */
 struct ina3221_data {
 	struct regmap *regmap;
 	struct regmap_field *fields[F_MAX_FIELDS];
-	int shunt_resistors[INA3221_NUM_CHANNELS];
+	struct ina3221_input inputs[INA3221_NUM_CHANNELS];
 	u32 reg_config;
 };
 
+static inline bool ina3221_is_enabled(struct ina3221_data *ina, int channel)
+{
+	return ina->reg_config & INA3221_CONFIG_CHx_EN(channel);
+}
+
+static ssize_t ina3221_show_label(struct device *dev,
+				  struct device_attribute *attr, char *buf)
+{
+	struct sensor_device_attribute *sd_attr = to_sensor_dev_attr(attr);
+	struct ina3221_data *ina = dev_get_drvdata(dev);
+	unsigned int channel = sd_attr->index;
+	struct ina3221_input *input = &ina->inputs[channel];
+
+	return snprintf(buf, PAGE_SIZE, "%s\n", input->label);
+}
+
+static ssize_t ina3221_show_enable(struct device *dev,
+				   struct device_attribute *attr, char *buf)
+{
+	struct sensor_device_attribute *sd_attr = to_sensor_dev_attr(attr);
+	struct ina3221_data *ina = dev_get_drvdata(dev);
+	unsigned int channel = sd_attr->index;
+
+	return snprintf(buf, PAGE_SIZE, "%d\n",
+			ina3221_is_enabled(ina, channel));
+}
+
+static ssize_t ina3221_set_enable(struct device *dev,
+				  struct device_attribute *attr,
+				  const char *buf, size_t count)
+{
+	struct sensor_device_attribute *sd_attr = to_sensor_dev_attr(attr);
+	struct ina3221_data *ina = dev_get_drvdata(dev);
+	unsigned int channel = sd_attr->index;
+	u16 config = ina->reg_config;
+	bool enable;
+	int ret;
+
+	ret = kstrtobool(buf, &enable);
+	if (ret)
+		return ret;
+
+	if (enable)
+		config |= INA3221_CONFIG_CHx_EN(channel);
+	else
+		config &= ~INA3221_CONFIG_CHx_EN(channel);
+
+	ret = regmap_write(ina->regmap, INA3221_CONFIG, config);
+	if (ret)
+		return ret;
+
+	ina->reg_config = config;
+
+	return count;
+}
+
 static int ina3221_read_value(struct ina3221_data *ina, unsigned int reg,
 			      int *val)
 {
@@ -122,8 +194,13 @@ static ssize_t ina3221_show_bus_voltage(struct device *dev,
 	struct sensor_device_attribute *sd_attr = to_sensor_dev_attr(attr);
 	struct ina3221_data *ina = dev_get_drvdata(dev);
 	unsigned int reg = sd_attr->index;
+	unsigned int channel = register_channel[reg];
 	int val, voltage_mv, ret;
 
+	/* No data for read-only attribute if channel is disabled */
+	if (!attr->store && !ina3221_is_enabled(ina, channel))
+		return -ENODATA;
+
 	ret = ina3221_read_value(ina, reg, &val);
 	if (ret)
 		return ret;
@@ -140,8 +217,13 @@ static ssize_t ina3221_show_shunt_voltage(struct device *dev,
 	struct sensor_device_attribute *sd_attr = to_sensor_dev_attr(attr);
 	struct ina3221_data *ina = dev_get_drvdata(dev);
 	unsigned int reg = sd_attr->index;
+	unsigned int channel = register_channel[reg];
 	int val, voltage_uv, ret;
 
+	/* No data for read-only attribute if channel is disabled */
+	if (!attr->store && !ina3221_is_enabled(ina, channel))
+		return -ENODATA;
+
 	ret = ina3221_read_value(ina, reg, &val);
 	if (ret)
 		return ret;
@@ -157,9 +239,14 @@ static ssize_t ina3221_show_current(struct device *dev,
 	struct ina3221_data *ina = dev_get_drvdata(dev);
 	unsigned int reg = sd_attr->index;
 	unsigned int channel = register_channel[reg];
-	int resistance_uo = ina->shunt_resistors[channel];
+	struct ina3221_input *input = &ina->inputs[channel];
+	int resistance_uo = input->shunt_resistor;
 	int val, current_ma, voltage_nv, ret;
 
+	/* No data for read-only attribute if channel is disabled */
+	if (!attr->store && !ina3221_is_enabled(ina, channel))
+		return -ENODATA;
+
 	ret = ina3221_read_value(ina, reg, &val);
 	if (ret)
 		return ret;
@@ -178,7 +265,8 @@ static ssize_t ina3221_set_current(struct device *dev,
 	struct ina3221_data *ina = dev_get_drvdata(dev);
 	unsigned int reg = sd_attr->index;
 	unsigned int channel = register_channel[reg];
-	int resistance_uo = ina->shunt_resistors[channel];
+	struct ina3221_input *input = &ina->inputs[channel];
+	int resistance_uo = input->shunt_resistor;
 	int val, current_ma, voltage_uv, ret;
 
 	ret = kstrtoint(buf, 0, &current_ma);
@@ -211,11 +299,9 @@ static ssize_t ina3221_show_shunt(struct device *dev,
 	struct sensor_device_attribute *sd_attr = to_sensor_dev_attr(attr);
 	struct ina3221_data *ina = dev_get_drvdata(dev);
 	unsigned int channel = sd_attr->index;
-	unsigned int resistance_uo;
+	struct ina3221_input *input = &ina->inputs[channel];
 
-	resistance_uo = ina->shunt_resistors[channel];
-
-	return snprintf(buf, PAGE_SIZE, "%d\n", resistance_uo);
+	return snprintf(buf, PAGE_SIZE, "%d\n", input->shunt_resistor);
 }
 
 static ssize_t ina3221_set_shunt(struct device *dev,
@@ -225,6 +311,7 @@ static ssize_t ina3221_set_shunt(struct device *dev,
 	struct sensor_device_attribute *sd_attr = to_sensor_dev_attr(attr);
 	struct ina3221_data *ina = dev_get_drvdata(dev);
 	unsigned int channel = sd_attr->index;
+	struct ina3221_input *input = &ina->inputs[channel];
 	int val;
 	int ret;
 
@@ -234,7 +321,7 @@ static ssize_t ina3221_set_shunt(struct device *dev,
 
 	val = clamp_val(val, 1, INT_MAX);
 
-	ina->shunt_resistors[channel] = val;
+	input->shunt_resistor = val;
 
 	return count;
 }
@@ -255,6 +342,22 @@ static ssize_t ina3221_show_alert(struct device *dev,
 	return snprintf(buf, PAGE_SIZE, "%d\n", regval);
 }
 
+/* input channel label */
+static SENSOR_DEVICE_ATTR(in1_label, 0444,
+		ina3221_show_label, NULL, INA3221_CHANNEL1);
+static SENSOR_DEVICE_ATTR(in2_label, 0444,
+		ina3221_show_label, NULL, INA3221_CHANNEL2);
+static SENSOR_DEVICE_ATTR(in3_label, 0444,
+		ina3221_show_label, NULL, INA3221_CHANNEL3);
+
+/* voltage channel enable */
+static SENSOR_DEVICE_ATTR(in1_enable, 0644,
+		ina3221_show_enable, ina3221_set_enable, INA3221_CHANNEL1);
+static SENSOR_DEVICE_ATTR(in2_enable, 0644,
+		ina3221_show_enable, ina3221_set_enable, INA3221_CHANNEL2);
+static SENSOR_DEVICE_ATTR(in3_enable, 0644,
+		ina3221_show_enable, ina3221_set_enable, INA3221_CHANNEL3);
+
 /* bus voltage */
 static SENSOR_DEVICE_ATTR(in1_input, S_IRUGO,
 		ina3221_show_bus_voltage, NULL, INA3221_BUS1);
@@ -320,7 +423,9 @@ static SENSOR_DEVICE_ATTR(in6_input, S_IRUGO,
 		ina3221_show_shunt_voltage, NULL, INA3221_SHUNT3);
 
 static struct attribute *ina3221_attrs[] = {
-	/* channel 1 */
+	/* channel 1 -- make sure label at first */
+	&sensor_dev_attr_in1_label.dev_attr.attr,
+	&sensor_dev_attr_in1_enable.dev_attr.attr,
 	&sensor_dev_attr_in1_input.dev_attr.attr,
 	&sensor_dev_attr_curr1_input.dev_attr.attr,
 	&sensor_dev_attr_shunt1_resistor.dev_attr.attr,
@@ -330,7 +435,9 @@ static struct attribute *ina3221_attrs[] = {
 	&sensor_dev_attr_curr1_max_alarm.dev_attr.attr,
 	&sensor_dev_attr_in4_input.dev_attr.attr,
 
-	/* channel 2 */
+	/* channel 2 -- make sure label at first */
+	&sensor_dev_attr_in2_label.dev_attr.attr,
+	&sensor_dev_attr_in2_enable.dev_attr.attr,
 	&sensor_dev_attr_in2_input.dev_attr.attr,
 	&sensor_dev_attr_curr2_input.dev_attr.attr,
 	&sensor_dev_attr_shunt2_resistor.dev_attr.attr,
@@ -340,7 +447,9 @@ static struct attribute *ina3221_attrs[] = {
 	&sensor_dev_attr_curr2_max_alarm.dev_attr.attr,
 	&sensor_dev_attr_in5_input.dev_attr.attr,
 
-	/* channel 3 */
+	/* channel 3 -- make sure label at first */
+	&sensor_dev_attr_in3_label.dev_attr.attr,
+	&sensor_dev_attr_in3_enable.dev_attr.attr,
 	&sensor_dev_attr_in3_input.dev_attr.attr,
 	&sensor_dev_attr_curr3_input.dev_attr.attr,
 	&sensor_dev_attr_shunt3_resistor.dev_attr.attr,
@@ -352,7 +461,30 @@ static struct attribute *ina3221_attrs[] = {
 
 	NULL,
 };
-ATTRIBUTE_GROUPS(ina3221);
+
+static umode_t ina3221_attr_is_visible(struct kobject *kobj,
+				       struct attribute *attr, int n)
+{
+	const int max_attrs = ARRAY_SIZE(ina3221_attrs) - 1;
+	const int num_attrs = max_attrs / INA3221_NUM_CHANNELS;
+	struct device *dev = kobj_to_dev(kobj);
+	struct ina3221_data *ina = dev_get_drvdata(dev);
+	enum ina3221_channels channel = n / num_attrs;
+	struct ina3221_input *input = &ina->inputs[channel];
+	int index = n % num_attrs;
+
+	/* Hide label node if label is not provided */
+	if (index == 0 && !input->label)
+		return 0;
+
+	return attr->mode;
+}
+
+static const struct attribute_group ina3221_group = {
+	.is_visible = ina3221_attr_is_visible,
+	.attrs = ina3221_attrs,
+};
+__ATTRIBUTE_GROUPS(ina3221);
 
 static const struct regmap_range ina3221_yes_ranges[] = {
 	regmap_reg_range(INA3221_CONFIG, INA3221_BUS3),
@@ -372,6 +504,60 @@ static const struct regmap_config ina3221_regmap_config = {
 	.volatile_table = &ina3221_volatile_table,
 };
 
+static int ina3221_probe_child_from_dt(struct device *dev,
+				       struct device_node *child,
+				       struct ina3221_data *ina)
+{
+	struct ina3221_input *input;
+	u32 val;
+	int ret;
+
+	ret = of_property_read_u32(child, "reg", &val);
+	if (ret) {
+		dev_err(dev, "missing reg property of %s\n", child->name);
+		return ret;
+	} else if (val > INA3221_CHANNEL3) {
+		dev_err(dev, "invalid reg %d of %s\n", val, child->name);
+		return ret;
+	}
+
+	input = &ina->inputs[val];
+
+	/* Log the disconnected channel input */
+	if (!of_device_is_available(child)) {
+		input->disconnected = true;
+		return 0;
+	}
+
+	/* Save the connected input label if available */
+	of_property_read_string(child, "label", &input->label);
+
+	/* Overwrite default shunt resistor value optionally */
+	if (!of_property_read_u32(child, "shunt-resistor-micro-ohms", &val))
+		input->shunt_resistor = val;
+
+	return 0;
+}
+
+static int ina3221_probe_from_dt(struct device *dev, struct ina3221_data *ina)
+{
+	const struct device_node *np = dev->of_node;
+	struct device_node *child;
+	int ret;
+
+	/* Compatible with non-DT platforms */
+	if (!np)
+		return 0;
+
+	for_each_child_of_node(np, child) {
+		ret = ina3221_probe_child_from_dt(dev, child, ina);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
 static int ina3221_probe(struct i2c_client *client,
 			 const struct i2c_device_id *id)
 {
@@ -401,7 +587,13 @@ static int ina3221_probe(struct i2c_client *client,
 	}
 
 	for (i = 0; i < INA3221_NUM_CHANNELS; i++)
-		ina->shunt_resistors[i] = INA3221_RSHUNT_DEFAULT;
+		ina->inputs[i].shunt_resistor = INA3221_RSHUNT_DEFAULT;
+
+	ret = ina3221_probe_from_dt(dev, ina);
+	if (ret) {
+		dev_err(dev, "Unable to probe from device tree\n");
+		return ret;
+	}
 
 	ret = regmap_field_write(ina->fields[F_RST], true);
 	if (ret) {
@@ -409,6 +601,20 @@ static int ina3221_probe(struct i2c_client *client,
 		return ret;
 	}
 
+	/* Sync config register after reset */
+	ret = regmap_read(ina->regmap, INA3221_CONFIG, &ina->reg_config);
+	if (ret)
+		return ret;
+
+	/* Disable channels if their inputs are disconnected */
+	for (i = 0; i < INA3221_NUM_CHANNELS; i++) {
+		if (ina->inputs[i].disconnected)
+			ina->reg_config &= ~INA3221_CONFIG_CHx_EN(i);
+	}
+	ret = regmap_write(ina->regmap, INA3221_CONFIG, ina->reg_config);
+	if (ret)
+		return ret;
+
 	hwmon_dev = devm_hwmon_device_register_with_groups(dev,
 							   client->name,
 							   ina, ina3221_groups);
-- 
2.17.1

Re: [PATCH v8 2/2] hwmon: ina3221: Read channel input source info from DT

[Guenter Roeck]

Hi Nicolin,

On 09/28/2018 06:39 PM, Nicolin Chen wrote:
> An ina3221 chip has three input ports. Each port is used
> to measure the voltage and current of its input source.
> 
> The DT binding now has defined bindings for their input
> sources, so the driver should read these information and
> handle accordingly.
> 
> This patch adds a new structure of input source specific
> information including input source label, shunt resistor
> value and its connection status. It exposes these labels
> via in[123]_label sysfs nodes upon available, and also
> disables those channels where there are no input source
> being connected. Meanwhile, it also adds in[123]_enable
> sysfs nodes for users to get control of three channels,
> and returns -ENODATA code for any sensor read according
> to hwmon ABI.
> 
> Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com>

[ ... ]

> +
> +static ssize_t ina3221_set_enable(struct device *dev,
> +				  struct device_attribute *attr,
> +				  const char *buf, size_t count)
> +{
> +	struct sensor_device_attribute *sd_attr = to_sensor_dev_attr(attr);
> +	struct ina3221_data *ina = dev_get_drvdata(dev);
> +	unsigned int channel = sd_attr->index;
> +	u16 config = ina->reg_config;
> +	bool enable;
> +	int ret;
> +
> +	ret = kstrtobool(buf, &enable);
> +	if (ret)
> +		return ret;
> +
> +	if (enable)
> +		config |= INA3221_CONFIG_CHx_EN(channel);
> +	else
> +		config &= ~INA3221_CONFIG_CHx_EN(channel);
> +
> +	ret = regmap_write(ina->regmap, INA3221_CONFIG, config);
> +	if (ret)
> +		return ret;
> +
> +	ina->reg_config = config;
> +

Sorry it too me so long to realize this: The code above is racy.
There could be multiple threads enabling and disabling a channel.
Without a mutex, there is no guarantee that the final value of
reg_config matches the value written into the chip.

You'll have to introduce a mutex and implement something like

	...
	ret = kstrtobool(buf, &enable);
	if (ret)
		return ret;

	mutex_lock(&ina->update_lock);
	config = ina->reg_config;
	...
	ret = regmap_write(ina->regmap, INA3221_CONFIG, config);
	if (ret) {
		count = ret;
		goto error;
	}
	ina->reg_config = config;
error:
	mutex_unlock(&ina->update_lock);
	return count;

Guenter

Re: [PATCH v8 2/2] hwmon: ina3221: Read channel input source info from DT

[Nicolin Chen]

On Sun, Sep 30, 2018 at 01:55:18PM -0700, Guenter Roeck wrote:
> Hi Nicolin,
> 
> On 09/28/2018 06:39 PM, Nicolin Chen wrote:
> >An ina3221 chip has three input ports. Each port is used
> >to measure the voltage and current of its input source.
> >
> >The DT binding now has defined bindings for their input
> >sources, so the driver should read these information and
> >handle accordingly.
> >
> >This patch adds a new structure of input source specific
> >information including input source label, shunt resistor
> >value and its connection status. It exposes these labels
> >via in[123]_label sysfs nodes upon available, and also
> >disables those channels where there are no input source
> >being connected. Meanwhile, it also adds in[123]_enable
> >sysfs nodes for users to get control of three channels,
> >and returns -ENODATA code for any sensor read according
> >to hwmon ABI.
> >
> >Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com>
> 
> [ ... ]
> 
> >+
> >+static ssize_t ina3221_set_enable(struct device *dev,
> >+				  struct device_attribute *attr,
> >+				  const char *buf, size_t count)
> >+{
> >+	struct sensor_device_attribute *sd_attr = to_sensor_dev_attr(attr);
> >+	struct ina3221_data *ina = dev_get_drvdata(dev);
> >+	unsigned int channel = sd_attr->index;
> >+	u16 config = ina->reg_config;
> >+	bool enable;
> >+	int ret;
> >+
> >+	ret = kstrtobool(buf, &enable);
> >+	if (ret)
> >+		return ret;
> >+
> >+	if (enable)
> >+		config |= INA3221_CONFIG_CHx_EN(channel);
> >+	else
> >+		config &= ~INA3221_CONFIG_CHx_EN(channel);
> >+
> >+	ret = regmap_write(ina->regmap, INA3221_CONFIG, config);
> >+	if (ret)
> >+		return ret;
> >+
> >+	ina->reg_config = config;
> >+
> 
> Sorry it too me so long to realize this: The code above is racy.
> There could be multiple threads enabling and disabling a channel.
> Without a mutex, there is no guarantee that the final value of
> reg_config matches the value written into the chip.

Hmm..that's true...glad you found and pointed it out.

> You'll have to introduce a mutex and implement something like
> 	ret = kstrtobool(buf, &enable);
> 	if (ret)
> 		return ret;
> 
> 	mutex_lock(&ina->update_lock);
> 	config = ina->reg_config;
> 	...
> 	ret = regmap_write(ina->regmap, INA3221_CONFIG, config);
> 	if (ret) {
> 		count = ret;
> 		goto error;
> 	}
> 	ina->reg_config = config;
> error:
> 	mutex_unlock(&ina->update_lock);
> 	return count;

I would prefer to just add another regmap_read at the end for
the reg_config sync, and to use regmap_update_bits() for the
bit set/clear. It might not serialize things as the solution
above does but at least the reg_config would get the correct
value eventually. Since regmap has an internal mutex already,
we may get rid of another mutex by doing so.

I will send a v9 tomorrow.

Thanks for the review
Nicolin