[PATCH v5 0/4] hwmon: (ina3221) Implement PM runtime to save power

[PATCH v5 0/4] hwmon: (ina3221) Implement PM runtime to save power

[Nicolin Chen]

This series patches implement PM runtime feature in the ina3221 hwmon
driver (PATCH-4). However, PATCH-[1:3] are required to make sure that
the PM runtime feature would be functional and safe.

Changelog
v4->v5:
 * Dropped the change for hwmon core; Shifted all the patch indexes
 * Used i2c_client dev pointer for pm runtime callbacks (PATCH-4)
v3->v4:
 * Added generic pm runtime functions to hwmon class (PATCH-1)
 * Updated to pass pm pointer via _with_info API (PATCH-5)
v2->v3:
 * Dropped timeout dev_err messages as it's indicated in errno (PATCH-4)
 * Improved a dev_err message and comments (PATCH-5)
v1->v2:
 * Added device pointer check (PATCH-1)
 * Returned 0 for alert flags (PATCH-2)
 * Moved CVRF polling to data read routine (PATCH-4)
 * Bypassed i2c_client->dev in suspend/resume() (PATCH-5)

Nicolin Chen (4):
  hwmon: (ina3221) Check channel status for alarms attribute read
  hwmon: (ina3221) Serialize sysfs ABI accesses
  hwmon: (ina3221) Make sure data is ready before reading
  hwmon: (ina3221) Add PM runtime support

 drivers/hwmon/ina3221.c | 190 +++++++++++++++++++++++++++++++++++-----
 1 file changed, 166 insertions(+), 24 deletions(-)

-- 
2.17.1

[PATCH v5 1/4] hwmon: (ina3221) Check channel status for alarms attribute read

[Nicolin Chen]

There is nothing critically wrong to read these two attributes
without having a is_enabled() check at this point. But reading
the MASK_ENABLE register would clear the CVRF bit according to
the datasheet. So it'd be safer to fence for disabled channels
in order to add pm runtime feature.

Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com>
---
Changelog
v2->v5:
 * N/A
v1->v2:
 * Returned 0 for alert flags instead of -ENODATA

 drivers/hwmon/ina3221.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/hwmon/ina3221.c b/drivers/hwmon/ina3221.c
index d61688f04594..26cdf3342d80 100644
--- a/drivers/hwmon/ina3221.c
+++ b/drivers/hwmon/ina3221.c
@@ -200,6 +200,12 @@ static int ina3221_read_curr(struct device *dev, u32 attr,
 		return 0;
 	case hwmon_curr_crit_alarm:
 	case hwmon_curr_max_alarm:
+		/* No actual register read if channel is disabled */
+		if (!ina3221_is_enabled(ina, channel)) {
+			/* Return 0 for alert flags */
+			*val = 0;
+			return 0;
+		}
 		ret = regmap_field_read(ina->fields[reg], &regval);
 		if (ret)
 			return ret;
-- 
2.17.1

[PATCH v5 2/4] hwmon: (ina3221) Serialize sysfs ABI accesses

[Nicolin Chen]

This change adds a mutex to serialize accesses of sysfs attributes.

This is required when polling CVRF bit of the MASK/ENABLE register
because this bit is cleared on a read of this MASK/ENABLE register
or a write to CONFIG register, which means that this bit might be
accidentally cleared by reading other fields like alert flags.

So this patch adds a mutex lock to protect the write() and read()
callbacks. The read_string() callback won't need the lock since it
just returns the label without touching any hardware register.

Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com>
---
Changlog
v1->v5:
 * N/A

 drivers/hwmon/ina3221.c | 51 ++++++++++++++++++++++++++++++++++++-----
 1 file changed, 45 insertions(+), 6 deletions(-)

diff --git a/drivers/hwmon/ina3221.c b/drivers/hwmon/ina3221.c
index 26cdf3342d80..10e8347a3c80 100644
--- a/drivers/hwmon/ina3221.c
+++ b/drivers/hwmon/ina3221.c
@@ -18,6 +18,7 @@
 #include <linux/hwmon-sysfs.h>
 #include <linux/i2c.h>
 #include <linux/module.h>
+#include <linux/mutex.h>
 #include <linux/of.h>
 #include <linux/regmap.h>
 
@@ -94,12 +95,14 @@ struct ina3221_input {
  * @regmap: Register map of the device
  * @fields: Register fields of the device
  * @inputs: Array of channel input source specific structures
+ * @lock: mutex lock to serialize sysfs attribute accesses
  * @reg_config: Register value of INA3221_CONFIG
  */
 struct ina3221_data {
 	struct regmap *regmap;
 	struct regmap_field *fields[F_MAX_FIELDS];
 	struct ina3221_input inputs[INA3221_NUM_CHANNELS];
+	struct mutex lock;
 	u32 reg_config;
 };
 
@@ -265,29 +268,53 @@ static int ina3221_write_enable(struct device *dev, int channel, bool enable)
 static int ina3221_read(struct device *dev, enum hwmon_sensor_types type,
 			u32 attr, int channel, long *val)
 {
+	struct ina3221_data *ina = dev_get_drvdata(dev);
+	int ret;
+
+	mutex_lock(&ina->lock);
+
 	switch (type) {
 	case hwmon_in:
 		/* 0-align channel ID */
-		return ina3221_read_in(dev, attr, channel - 1, val);
+		ret = ina3221_read_in(dev, attr, channel - 1, val);
+		break;
 	case hwmon_curr:
-		return ina3221_read_curr(dev, attr, channel, val);
+		ret = ina3221_read_curr(dev, attr, channel, val);
+		break;
 	default:
-		return -EOPNOTSUPP;
+		ret = -EOPNOTSUPP;
+		break;
 	}
+
+	mutex_unlock(&ina->lock);
+
+	return ret;
 }
 
 static int ina3221_write(struct device *dev, enum hwmon_sensor_types type,
 			 u32 attr, int channel, long val)
 {
+	struct ina3221_data *ina = dev_get_drvdata(dev);
+	int ret;
+
+	mutex_lock(&ina->lock);
+
 	switch (type) {
 	case hwmon_in:
 		/* 0-align channel ID */
-		return ina3221_write_enable(dev, channel - 1, val);
+		ret = ina3221_write_enable(dev, channel - 1, val);
+		break;
 	case hwmon_curr:
-		return ina3221_write_curr(dev, attr, channel, val);
+		ret = ina3221_write_curr(dev, attr, channel, val);
+		break;
 	default:
-		return -EOPNOTSUPP;
+		ret = -EOPNOTSUPP;
+		break;
 	}
+
+	mutex_unlock(&ina->lock);
+
+	return ret;
 }
 
 static int ina3221_read_string(struct device *dev, enum hwmon_sensor_types type,
@@ -582,6 +609,7 @@ static int ina3221_probe(struct i2c_client *client,
 	if (ret)
 		return ret;
 
+	mutex_init(&ina->lock);
 	dev_set_drvdata(dev, ina);
 
 	hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name, ina,
@@ -589,12 +617,22 @@ static int ina3221_probe(struct i2c_client *client,
 							 ina3221_groups);
 	if (IS_ERR(hwmon_dev)) {
 		dev_err(dev, "Unable to register hwmon device\n");
+		mutex_destroy(&ina->lock);
 		return PTR_ERR(hwmon_dev);
 	}
 
 	return 0;
 }
 
+static int ina3221_remove(struct i2c_client *client)
+{
+	struct ina3221_data *ina = dev_get_drvdata(&client->dev);
+
+	mutex_destroy(&ina->lock);
+
+	return 0;
+}
+
 static int __maybe_unused ina3221_suspend(struct device *dev)
 {
 	struct ina3221_data *ina = dev_get_drvdata(dev);
@@ -663,6 +701,7 @@ MODULE_DEVICE_TABLE(i2c, ina3221_ids);
 
 static struct i2c_driver ina3221_i2c_driver = {
 	.probe = ina3221_probe,
+	.remove = ina3221_remove,
 	.driver = {
 		.name = INA3221_DRIVER_NAME,
 		.of_match_table = ina3221_of_match_table,
-- 
2.17.1

[PATCH v5 3/4] hwmon: (ina3221) Make sure data is ready before reading

[Nicolin Chen]

The data might need some time to get ready after channel enabling,
although the data register is always readable. The CVRF bit is to
indicate that data conversion is finished, so polling the CVRF bit
before data reading could ensure the result being valid.

An alternative way could be to wait for expected time between the
channel enabling and the data reading. And this could avoid extra
I2C communications. However, INA3221 seemly takes longer time than
what's stated in the datasheet. Test results show that sometimes
it couldn't finish data conversion in time.

So this patch plays safe by adding a CVRF polling to make sure the
data register is updated with the new data.

Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com>
---
Changelog
v3->v5:
 * N/A
v2->v3:
 * Dropped timeout dev_err messages as it's indicated in the errno
v1->v2:
 * Moved CVRF polling to data read routine
 * Added calculation of wait time based on conversion time setting

 drivers/hwmon/ina3221.c | 42 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/drivers/hwmon/ina3221.c b/drivers/hwmon/ina3221.c
index 10e8347a3c80..07dd6ef58d3e 100644
--- a/drivers/hwmon/ina3221.c
+++ b/drivers/hwmon/ina3221.c
@@ -44,6 +44,13 @@
 #define INA3221_CONFIG_MODE_SHUNT	BIT(0)
 #define INA3221_CONFIG_MODE_BUS		BIT(1)
 #define INA3221_CONFIG_MODE_CONTINUOUS	BIT(2)
+#define INA3221_CONFIG_VSH_CT_SHIFT	3
+#define INA3221_CONFIG_VSH_CT_MASK	GENMASK(5, 3)
+#define INA3221_CONFIG_VSH_CT(x)	(((x) & GENMASK(5, 3)) >> 3)
+#define INA3221_CONFIG_VBUS_CT_SHIFT	6
+#define INA3221_CONFIG_VBUS_CT_MASK	GENMASK(8, 6)
+#define INA3221_CONFIG_VBUS_CT(x)	(((x) & GENMASK(8, 6)) >> 6)
+#define INA3221_CONFIG_CHs_EN_MASK	GENMASK(14, 12)
 #define INA3221_CONFIG_CHx_EN(x)	BIT(14 - (x))
 
 #define INA3221_RSHUNT_DEFAULT		10000
@@ -52,6 +59,9 @@ enum ina3221_fields {
 	/* Configuration */
 	F_RST,
 
+	/* Status Flags */
+	F_CVRF,
+
 	/* Alert Flags */
 	F_WF3, F_WF2, F_WF1,
 	F_CF3, F_CF2, F_CF1,
@@ -63,6 +73,7 @@ enum ina3221_fields {
 static const struct reg_field ina3221_reg_fields[] = {
 	[F_RST] = REG_FIELD(INA3221_CONFIG, 15, 15),
 
+	[F_CVRF] = REG_FIELD(INA3221_MASK_ENABLE, 0, 0),
 	[F_WF3] = REG_FIELD(INA3221_MASK_ENABLE, 3, 3),
 	[F_WF2] = REG_FIELD(INA3221_MASK_ENABLE, 4, 4),
 	[F_WF1] = REG_FIELD(INA3221_MASK_ENABLE, 5, 5),
@@ -111,6 +122,28 @@ static inline bool ina3221_is_enabled(struct ina3221_data *ina, int channel)
 	return ina->reg_config & INA3221_CONFIG_CHx_EN(channel);
 }
 
+/* Lookup table for Bus and Shunt conversion times in usec */
+static const u16 ina3221_conv_time[] = {
+	140, 204, 332, 588, 1100, 2116, 4156, 8244,
+};
+
+static inline int ina3221_wait_for_data(struct ina3221_data *ina)
+{
+	u32 channels = hweight16(ina->reg_config & INA3221_CONFIG_CHs_EN_MASK);
+	u32 vbus_ct_idx = INA3221_CONFIG_VBUS_CT(ina->reg_config);
+	u32 vsh_ct_idx = INA3221_CONFIG_VSH_CT(ina->reg_config);
+	u32 vbus_ct = ina3221_conv_time[vbus_ct_idx];
+	u32 vsh_ct = ina3221_conv_time[vsh_ct_idx];
+	u32 wait, cvrf;
+
+	/* Calculate total conversion time */
+	wait = channels * (vbus_ct + vsh_ct);
+
+	/* Polling the CVRF bit to make sure read data is ready */
+	return regmap_field_read_poll_timeout(ina->fields[F_CVRF],
+					      cvrf, cvrf, wait, 100000);
+}
+
 static int ina3221_read_value(struct ina3221_data *ina, unsigned int reg,
 			      int *val)
 {
@@ -150,6 +183,10 @@ static int ina3221_read_in(struct device *dev, u32 attr, int channel, long *val)
 		if (!ina3221_is_enabled(ina, channel))
 			return -ENODATA;
 
+		ret = ina3221_wait_for_data(ina);
+		if (ret)
+			return ret;
+
 		ret = ina3221_read_value(ina, reg, &regval);
 		if (ret)
 			return ret;
@@ -189,6 +226,11 @@ static int ina3221_read_curr(struct device *dev, u32 attr,
 	case hwmon_curr_input:
 		if (!ina3221_is_enabled(ina, channel))
 			return -ENODATA;
+
+		ret = ina3221_wait_for_data(ina);
+		if (ret)
+			return ret;
+
 		/* fall through */
 	case hwmon_curr_crit:
 	case hwmon_curr_max:
-- 
2.17.1

[PATCH v5 4/4] hwmon: (ina3221) Add PM runtime support

[Nicolin Chen]

If all three channels are disabled via in[123]_enable ABI,
the driver could suspend the chip for power saving purpose.

So this patch adds the PM runtime support in order to gain
more power control than system suspend and resume use case.

For PM runtime, there are a few related changes happening:
1) Added a new pm_dev device pointer for all the PM runtime
   callbacks. This is because hwmon core registers a child
   device for each hwmon driver and passes it back to each
   driver. So there might be a mismatch between two device
   pointers in the driver if mixing using them.
2) Added a check in ina3221_is_enabled() to make sure that
   the chip is resumed.
3) Bypassed the unchanged status in ina3221_write_enable()
   in order to keep the PM runtime refcount being matched.
4) Removed the reset routine in the probe() by calling the
   resume() via pm_runtime_get_sync() instead, as they're
   similar. It's also necessary to do so to match initial
   PM refcount with the number of enabled channels.

Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com>
---
Changelog
v4->v5:
 * Dropped the code of passing pm pointer via _info API
 ** Moved all changes back to the status of v3
 * Used i2c_client dev pointer for pm runtime callbacks
v3->v4:
 * Passed pm pointer via _with_info API instead the i2c driver
v2->v3:
 * Improved a dev_err message
 * Added comments at pm_runtime_put_noidle() callbacks
 * Added pm_runtime header file in an alphabetical order
v1->v2:
 * Bypassed i2c_client->dev in suspend/resume()
 * Added a missing '\n' in one dev_err()

 drivers/hwmon/ina3221.c | 93 ++++++++++++++++++++++++++++++++---------
 1 file changed, 74 insertions(+), 19 deletions(-)

diff --git a/drivers/hwmon/ina3221.c b/drivers/hwmon/ina3221.c
index 07dd6ef58d3e..17a57dbc0424 100644
--- a/drivers/hwmon/ina3221.c
+++ b/drivers/hwmon/ina3221.c
@@ -20,6 +20,7 @@
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/of.h>
+#include <linux/pm_runtime.h>
 #include <linux/regmap.h>
 
 #define INA3221_DRIVER_NAME		"ina3221"
@@ -53,6 +54,7 @@
 #define INA3221_CONFIG_CHs_EN_MASK	GENMASK(14, 12)
 #define INA3221_CONFIG_CHx_EN(x)	BIT(14 - (x))
 
+#define INA3221_CONFIG_DEFAULT		0x7127
 #define INA3221_RSHUNT_DEFAULT		10000
 
 enum ina3221_fields {
@@ -103,6 +105,7 @@ struct ina3221_input {
 
 /**
  * struct ina3221_data - device specific information
+ * @pm_dev: Device pointer for pm runtime
  * @regmap: Register map of the device
  * @fields: Register fields of the device
  * @inputs: Array of channel input source specific structures
@@ -110,6 +113,7 @@ struct ina3221_input {
  * @reg_config: Register value of INA3221_CONFIG
  */
 struct ina3221_data {
+	struct device *pm_dev;
 	struct regmap *regmap;
 	struct regmap_field *fields[F_MAX_FIELDS];
 	struct ina3221_input inputs[INA3221_NUM_CHANNELS];
@@ -119,7 +123,8 @@ struct ina3221_data {
 
 static inline bool ina3221_is_enabled(struct ina3221_data *ina, int channel)
 {
-	return ina->reg_config & INA3221_CONFIG_CHx_EN(channel);
+	return pm_runtime_active(ina->pm_dev) &&
+	       (ina->reg_config & INA3221_CONFIG_CHx_EN(channel));
 }
 
 /* Lookup table for Bus and Shunt conversion times in usec */
@@ -290,21 +295,48 @@ static int ina3221_write_enable(struct device *dev, int channel, bool enable)
 {
 	struct ina3221_data *ina = dev_get_drvdata(dev);
 	u16 config, mask = INA3221_CONFIG_CHx_EN(channel);
+	u16 config_old = ina->reg_config & mask;
 	int ret;
 
 	config = enable ? mask : 0;
 
+	/* Bypass if enable status is not being changed */
+	if (config_old == config)
+		return 0;
+
+	/* For enabling routine, increase refcount and resume() at first */
+	if (enable) {
+		ret = pm_runtime_get_sync(ina->pm_dev);
+		if (ret < 0) {
+			dev_err(dev, "Failed to get PM runtime\n");
+			return ret;
+		}
+	}
+
 	/* Enable or disable the channel */
 	ret = regmap_update_bits(ina->regmap, INA3221_CONFIG, mask, config);
 	if (ret)
-		return ret;
+		goto fail;
 
 	/* Cache the latest config register value */
 	ret = regmap_read(ina->regmap, INA3221_CONFIG, &ina->reg_config);
 	if (ret)
-		return ret;
+		goto fail;
+
+	/* For disabling routine, decrease refcount or suspend() at last */
+	if (!enable)
+		pm_runtime_put_sync(ina->pm_dev);
 
 	return 0;
+
+fail:
+	if (enable) {
+		dev_err(dev, "Failed to enable channel %d: error %d\n",
+			channel, ret);
+		pm_runtime_put_sync(ina->pm_dev);
+	}
+
+	return ret;
 }
 
 static int ina3221_read(struct device *dev, enum hwmon_sensor_types type,
@@ -631,44 +663,65 @@ static int ina3221_probe(struct i2c_client *client,
 		return ret;
 	}
 
-	ret = regmap_field_write(ina->fields[F_RST], true);
-	if (ret) {
-		dev_err(dev, "Unable to reset device\n");
-		return ret;
-	}
-
-	/* Sync config register after reset */
-	ret = regmap_read(ina->regmap, INA3221_CONFIG, &ina->reg_config);
-	if (ret)
-		return ret;
+	/* The driver will be reset, so use reset value */
+	ina->reg_config = INA3221_CONFIG_DEFAULT;
 
 	/* 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;
 
+	ina->pm_dev = dev;
 	mutex_init(&ina->lock);
 	dev_set_drvdata(dev, ina);
 
+	/* Enable PM runtime -- status is suspended by default */
+	pm_runtime_enable(ina->pm_dev);
+
+	/* Initialize (resume) the device */
+	for (i = 0; i < INA3221_NUM_CHANNELS; i++) {
+		if (ina->inputs[i].disconnected)
+			continue;
+		/* Match the refcount with number of enabled channels */
+		ret = pm_runtime_get_sync(ina->pm_dev);
+		if (ret < 0)
+			goto fail;
+	}
+
 	hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name, ina,
 							 &ina3221_chip_info,
 							 ina3221_groups);
 	if (IS_ERR(hwmon_dev)) {
 		dev_err(dev, "Unable to register hwmon device\n");
-		mutex_destroy(&ina->lock);
-		return PTR_ERR(hwmon_dev);
+		ret = PTR_ERR(hwmon_dev);
+		goto fail;
 	}
 
 	return 0;
+
+fail:
+	pm_runtime_disable(ina->pm_dev);
+	pm_runtime_set_suspended(ina->pm_dev);
+	/* pm_runtime_put_noidle() will decrease the PM refcount until 0 */
+	for (i = 0; i < INA3221_NUM_CHANNELS; i++)
+		pm_runtime_put_noidle(ina->pm_dev);
+	mutex_destroy(&ina->lock);
+
+	return ret;
 }
 
 static int ina3221_remove(struct i2c_client *client)
 {
 	struct ina3221_data *ina = dev_get_drvdata(&client->dev);
+	int i;
+
+	pm_runtime_disable(ina->pm_dev);
+	pm_runtime_set_suspended(ina->pm_dev);
+
+	/* pm_runtime_put_noidle() will decrease the PM refcount until 0 */
+	for (i = 0; i < INA3221_NUM_CHANNELS; i++)
+		pm_runtime_put_noidle(ina->pm_dev);
 
 	mutex_destroy(&ina->lock);
 
@@ -726,7 +779,9 @@ static int __maybe_unused ina3221_resume(struct device *dev)
 }
 
 static const struct dev_pm_ops ina3221_pm = {
-	SET_SYSTEM_SLEEP_PM_OPS(ina3221_suspend, ina3221_resume)
+	SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
+				pm_runtime_force_resume)
+	SET_RUNTIME_PM_OPS(ina3221_suspend, ina3221_resume, NULL)
 };
 
 static const struct of_device_id ina3221_of_match_table[] = {
-- 
2.17.1

Re: [PATCH v5 0/4] hwmon: (ina3221) Implement PM runtime to save power

[Guenter Roeck]

On Mon, Nov 05, 2018 at 12:48:39PM -0800, Nicolin Chen wrote:
> This series patches implement PM runtime feature in the ina3221 hwmon
> driver (PATCH-4). However, PATCH-[1:3] are required to make sure that
> the PM runtime feature would be functional and safe.
> 

Series applied to hwmon-next.

Thanks,
Guenter

> Changelog
> v4->v5:
>  * Dropped the change for hwmon core; Shifted all the patch indexes
>  * Used i2c_client dev pointer for pm runtime callbacks (PATCH-4)
> v3->v4:
>  * Added generic pm runtime functions to hwmon class (PATCH-1)
>  * Updated to pass pm pointer via _with_info API (PATCH-5)
> v2->v3:
>  * Dropped timeout dev_err messages as it's indicated in errno (PATCH-4)
>  * Improved a dev_err message and comments (PATCH-5)
> v1->v2:
>  * Added device pointer check (PATCH-1)
>  * Returned 0 for alert flags (PATCH-2)
>  * Moved CVRF polling to data read routine (PATCH-4)
>  * Bypassed i2c_client->dev in suspend/resume() (PATCH-5)
> 
> Nicolin Chen (4):
>   hwmon: (ina3221) Check channel status for alarms attribute read
>   hwmon: (ina3221) Serialize sysfs ABI accesses
>   hwmon: (ina3221) Make sure data is ready before reading
>   hwmon: (ina3221) Add PM runtime support
> 
>  drivers/hwmon/ina3221.c | 190 +++++++++++++++++++++++++++++++++++-----
>  1 file changed, 166 insertions(+), 24 deletions(-)
> 
> -- 
> 2.17.1
>