[PATCH v5 1/4] hwmon: max31827: Handle new properties from the devicetree

[PATCH v5 1/4] hwmon: max31827: Handle new properties from the devicetree

[Daniel Matyas]

Used fwnode to retrieve data from the devicetree in the init_client
function.

If the uint32 properties are not present, the default values are used
for max31827 chip.

Signed-off-by: Daniel Matyas <daniel.matyas@analog.com>
---

v4 -> v5: Removed comment from __bf_shf() and used ffs() instead of
ffs64().
Added tabs where there was a need.
Removed i2c_client from private structure. In init_client() passed
device structure, because I only used that.
Changed error message when the data in adi,fault-q is invalid.
Fwnode is initialized in init_client().

v3 -> v4: Renamed property names to correspond with binding.

v2 -> v3: Separated patch into 2. Fixed 'WARNING: Unexpected
indentation.'
Reported-by: kernel test robot <lkp@intel.com>

v2: Added patch.

 Documentation/hwmon/max31827.rst | 48 +++++++++++++++++++-----
 drivers/hwmon/max31827.c         | 64 +++++++++++++++++++++++++++++---
 2 files changed, 97 insertions(+), 15 deletions(-)

diff --git a/Documentation/hwmon/max31827.rst b/Documentation/hwmon/max31827.rst
index 9a1055a007cf..a8bbfb85dd02 100644
--- a/Documentation/hwmon/max31827.rst
+++ b/Documentation/hwmon/max31827.rst
@@ -52,13 +52,21 @@ MAX31827 has low and over temperature alarms with an effective value and a
 hysteresis value: -40 and -30 degrees for under temperature alarm and +100 and
 +90 degrees for over temperature alarm.
 
-The alarm can be configured in comparator and interrupt mode. Currently only
-comparator mode is implemented. In Comparator mode, the OT/UT status bits have a
-value of 1 when the temperature rises above the TH value or falls below TL,
-which is also subject to the Fault Queue selection. OT status returns to 0 when
-the temperature drops below the TH_HYST value or when shutdown mode is entered.
-Similarly, UT status returns to 0 when the temperature rises above TL_HYST value
-or when shutdown mode is entered.
+The alarm can be configured in comparator and interrupt mode from the
+devicetree. In Comparator mode, the OT/UT status bits have a value of 1 when the
+temperature rises above the TH value or falls below TL, which is also subject to
+the Fault Queue selection. OT status returns to 0 when the temperature drops
+below the TH_HYST value or when shutdown mode is entered. Similarly, UT status
+returns to 0 when the temperature rises above TL_HYST value or when shutdown
+mode is entered.
+
+In interrupt mode exceeding TH also sets OT status to 1, which remains set until
+a read operation is performed on the configuration/status register (max or min
+attribute); at this point, it returns to 0. Once OT status is set to 1 from
+exceeding TH and reset, it is set to 1 again only when the temperature drops
+below TH_HYST. The output remains asserted until it is reset by a read. It is
+set again if the temperature rises above TH, and so on. The same logic applies
+to the operation of the UT status bit.
 
 Putting the MAX31827 into shutdown mode also resets the OT/UT status bits. Note
 that if the mode is changed while OT/UT status bits are set, an OT/UT status
@@ -68,6 +76,18 @@ clear the status bits before changing the operating mode.
 
 The conversions can be manual with the one-shot functionality and automatic with
 a set frequency. When powered on, the chip measures temperatures with 1 conv/s.
+The conversion rate can be modified with update_interval attribute of the chip.
+Conversion/second = 1/update_interval. Thus, the available options according to
+the data sheet are:
+
+- 64000 (ms) = 1 conv/64 sec
+- 32000 (ms) = 1 conv/32 sec
+- 16000 (ms) = 1 conv/16 sec
+- 4000 (ms) = 1 conv/4 sec
+- 1000 (ms) = 1 conv/sec (default)
+- 250 (ms) = 4 conv/sec
+- 125 (ms) = 8 conv/sec
+
 Enabling the device when it is already enabled has the side effect of setting
 the conversion frequency to 1 conv/s. The conversion time varies depending on
 the resolution. The conversion time doubles with every bit of increased
@@ -83,8 +103,18 @@ in the writing of alarm values too. For positive numbers the user-input value
 will always be rounded down to the nearest possible value, for negative numbers
 the user-input will always be rounded up to the nearest possible value.
 
+Bus timeout resets the I2C-compatible interface when SCL is low for more than
+30ms (nominal).
+
+Alarm polarity determines if the active state of the alarm is low or high. The
+behavior for both settings is dependent on the Fault Queue setting. The ALARM
+pin is an open-drain output and requires a pullup resistor to operate.
+
+The Fault Queue bits select how many consecutive temperature faults must occur
+before overtemperature or undertemperature faults are indicated in the
+corresponding status bits.
+
 Notes
 -----
 
-Currently fault queue, alarm polarity and resolution cannot be modified.
-PEC is not implemented either.
+PEC and resolution are not implemented.
diff --git a/drivers/hwmon/max31827.c b/drivers/hwmon/max31827.c
index 614bbf5d25fa..7976d668ffd4 100644
--- a/drivers/hwmon/max31827.c
+++ b/drivers/hwmon/max31827.c
@@ -12,6 +12,13 @@
 #include <linux/i2c.h>
 #include <linux/mutex.h>
 #include <linux/regmap.h>
+#include <linux/of_device.h>
+
+#define max31827__bf_shf(x)			 \
+	({					 \
+		typeof(x) x_ = (x);		 \
+		((x_) != 0) ? __ffs(x_) : 0x0; \
+	})
 
 #define MAX31827_T_REG			0x0
 #define MAX31827_CONFIGURATION_REG	0x2
@@ -22,6 +29,11 @@
 
 #define MAX31827_CONFIGURATION_1SHOT_MASK	BIT(0)
 #define MAX31827_CONFIGURATION_CNV_RATE_MASK	GENMASK(3, 1)
+#define MAX31827_CONFIGURATION_TIMEOUT_MASK	BIT(5)
+#define MAX31827_CONFIGURATION_RESOLUTION_MASK	GENMASK(7, 6)
+#define MAX31827_CONFIGURATION_ALRM_POL_MASK	BIT(8)
+#define MAX31827_CONFIGURATION_COMP_INT_MASK	BIT(9)
+#define MAX31827_CONFIGURATION_FLT_Q_MASK	GENMASK(11, 10)
 #define MAX31827_CONFIGURATION_U_TEMP_STAT_MASK	BIT(14)
 #define MAX31827_CONFIGURATION_O_TEMP_STAT_MASK	BIT(15)
 
@@ -361,14 +373,54 @@ static int max31827_write(struct device *dev, enum hwmon_sensor_types type,
 	return -EOPNOTSUPP;
 }
 
-static int max31827_init_client(struct max31827_state *st)
+static int max31827_init_client(struct max31827_state *st,
+				struct device *dev)
 {
+	struct fwnode_handle *fwnode;
+	unsigned int res = 0;
+	u32 data, lsb_idx;
+	bool prop;
+	int ret;
+
+	fwnode = dev_fwnode(dev);
+
 	st->enable = true;
+	res |= MAX31827_DEVICE_ENABLE(1);
+
+	res |= MAX31827_CONFIGURATION_RESOLUTION_MASK;
+
+	prop = fwnode_property_read_bool(fwnode, "adi,comp-int");
+	res |= FIELD_PREP(MAX31827_CONFIGURATION_COMP_INT_MASK, prop);
+
+	prop = fwnode_property_read_bool(fwnode, "adi,timeout-enable");
+	res |= FIELD_PREP(MAX31827_CONFIGURATION_TIMEOUT_MASK, !prop);
+
+	if (fwnode_property_present(fwnode, "adi,alarm-pol")) {
+		ret = fwnode_property_read_u32(fwnode, "adi,alarm-pol", &data);
+		if (ret)
+			return ret;
+
+		res |= FIELD_PREP(MAX31827_CONFIGURATION_ALRM_POL_MASK, !!data);
+	}
+
+	if (fwnode_property_present(fwnode, "adi,fault-q")) {
+		ret = fwnode_property_read_u32(fwnode, "adi,fault-q", &data);
+		if (ret)
+			return ret;
+
+		/*
+		 * Convert the desired fault queue into register bits.
+		 */
+		lsb_idx = max31827__bf_shf(data);
+		if (lsb_idx > 3 || data != BIT(lsb_idx)) {
+			dev_err(dev, "Invalid data in adi,fault-q\n");
+			return -EINVAL;
+		}
+
+		res |= FIELD_PREP(MAX31827_CONFIGURATION_FLT_Q_MASK, lsb_idx);
+	}
 
-	return regmap_update_bits(st->regmap, MAX31827_CONFIGURATION_REG,
-				  MAX31827_CONFIGURATION_1SHOT_MASK |
-					  MAX31827_CONFIGURATION_CNV_RATE_MASK,
-				  MAX31827_DEVICE_ENABLE(1));
+	return regmap_write(st->regmap, MAX31827_CONFIGURATION_REG, res);
 }
 
 static const struct hwmon_channel_info *max31827_info[] = {
@@ -412,7 +464,7 @@ static int max31827_probe(struct i2c_client *client)
 		return dev_err_probe(dev, PTR_ERR(st->regmap),
 				     "Failed to allocate regmap.\n");
 
-	err = max31827_init_client(st);
+	err = max31827_init_client(st, dev);
 	if (err)
 		return err;
 
-- 
2.34.1

[PATCH v5 2/4] hwmon: max31827: Add support for max31828 and max31829

[Daniel Matyas]

When adi,flt-q and/or adi,alrm-pol are not mentioned,
the default configuration is loaded.

Signed-off-by: Daniel Matyas <daniel.matyas@analog.com>
---

v4 -> v5: Passed i2c_client to init_client(), because I needed it to
retrieve device id.
Used a simple if to load default configuration. No more switch.

v3 -> v4: No change.

v3: Added patch.

 drivers/hwmon/max31827.c | 51 +++++++++++++++++++++++++++++++---------
 1 file changed, 40 insertions(+), 11 deletions(-)

diff --git a/drivers/hwmon/max31827.c b/drivers/hwmon/max31827.c
index 7976d668ffd4..446232fa1710 100644
--- a/drivers/hwmon/max31827.c
+++ b/drivers/hwmon/max31827.c
@@ -39,10 +39,15 @@
 
 #define MAX31827_12_BIT_CNV_TIME	140
 
+#define MAX31827_ALRM_POL_HIGH	0x1
+#define MAX31827_FLT_Q_4	0x2
+
 #define MAX31827_16_BIT_TO_M_DGR(x)	(sign_extend32(x, 15) * 1000 / 16)
 #define MAX31827_M_DGR_TO_16_BIT(x)	(((x) << 4) / 1000)
 #define MAX31827_DEVICE_ENABLE(x)	((x) ? 0xA : 0x0)
 
+enum chips { max31827, max31828, max31829 };
+
 enum max31827_cnv {
 	MAX31827_CNV_1_DIV_64_HZ = 1,
 	MAX31827_CNV_1_DIV_32_HZ,
@@ -373,12 +378,22 @@ static int max31827_write(struct device *dev, enum hwmon_sensor_types type,
 	return -EOPNOTSUPP;
 }
 
+static const struct i2c_device_id max31827_i2c_ids[] = {
+	{ "max31827", max31827 },
+	{ "max31828", max31828 },
+	{ "max31829", max31829 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, max31827_i2c_ids);
+
 static int max31827_init_client(struct max31827_state *st,
-				struct device *dev)
+				struct i2c_client *client)
 {
+	struct device *dev = &client->dev;
 	struct fwnode_handle *fwnode;
 	unsigned int res = 0;
 	u32 data, lsb_idx;
+	enum chips type;
 	bool prop;
 	int ret;
 
@@ -395,13 +410,20 @@ static int max31827_init_client(struct max31827_state *st,
 	prop = fwnode_property_read_bool(fwnode, "adi,timeout-enable");
 	res |= FIELD_PREP(MAX31827_CONFIGURATION_TIMEOUT_MASK, !prop);
 
+	if (dev->of_node)
+		type = (enum chips)of_device_get_match_data(dev);
+	else
+		type = i2c_match_id(max31827_i2c_ids, client)->driver_data;
+
 	if (fwnode_property_present(fwnode, "adi,alarm-pol")) {
 		ret = fwnode_property_read_u32(fwnode, "adi,alarm-pol", &data);
 		if (ret)
 			return ret;
 
 		res |= FIELD_PREP(MAX31827_CONFIGURATION_ALRM_POL_MASK, !!data);
-	}
+	} else if (type == max31829)
+		res |= FIELD_PREP(MAX31827_CONFIGURATION_ALRM_POL_MASK,
+				  MAX31827_ALRM_POL_HIGH);
 
 	if (fwnode_property_present(fwnode, "adi,fault-q")) {
 		ret = fwnode_property_read_u32(fwnode, "adi,fault-q", &data);
@@ -418,7 +440,9 @@ static int max31827_init_client(struct max31827_state *st,
 		}
 
 		res |= FIELD_PREP(MAX31827_CONFIGURATION_FLT_Q_MASK, lsb_idx);
-	}
+	} else if ((type == max31828) || (type == max31829))
+		res |= FIELD_PREP(MAX31827_CONFIGURATION_FLT_Q_MASK,
+				  MAX31827_FLT_Q_4);
 
 	return regmap_write(st->regmap, MAX31827_CONFIGURATION_REG, res);
 }
@@ -464,7 +488,7 @@ static int max31827_probe(struct i2c_client *client)
 		return dev_err_probe(dev, PTR_ERR(st->regmap),
 				     "Failed to allocate regmap.\n");
 
-	err = max31827_init_client(st, dev);
+	err = max31827_init_client(st, client);
 	if (err)
 		return err;
 
@@ -475,14 +499,19 @@ static int max31827_probe(struct i2c_client *client)
 	return PTR_ERR_OR_ZERO(hwmon_dev);
 }
 
-static const struct i2c_device_id max31827_i2c_ids[] = {
-	{ "max31827", 0 },
-	{ }
-};
-MODULE_DEVICE_TABLE(i2c, max31827_i2c_ids);
-
 static const struct of_device_id max31827_of_match[] = {
-	{ .compatible = "adi,max31827" },
+	{
+		.compatible = "adi,max31827",
+		.data = (void *)max31827
+	},
+	{
+		.compatible = "adi,max31828",
+		.data = (void *)max31828
+	},
+	{
+		.compatible = "adi,max31829",
+		.data = (void *)max31829
+	},
 	{ }
 };
 MODULE_DEVICE_TABLE(of, max31827_of_match);
-- 
2.34.1

[PATCH v5 3/4] hwmon: max31827: Update bits with shutdown_write()

[Daniel Matyas]

Added 'mask' parameter to the shutdown_write() function. Now it can
either write or update bits, depending on the value of mask. This is
needed, because for alarms a write is necessary, but for resolution only
the resolution bits should be updated.

Signed-off-by: Daniel Matyas <daniel.matyas@analog.com>
---

v4 -> v5: No change.

v4: Added patch.

 drivers/hwmon/max31827.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/hwmon/max31827.c b/drivers/hwmon/max31827.c
index 446232fa1710..8ba387b51157 100644
--- a/drivers/hwmon/max31827.c
+++ b/drivers/hwmon/max31827.c
@@ -84,7 +84,7 @@ static const struct regmap_config max31827_regmap = {
 };
 
 static int shutdown_write(struct max31827_state *st, unsigned int reg,
-			  unsigned int val)
+			  unsigned int mask, unsigned int val)
 {
 	unsigned int cfg;
 	unsigned int cnv_rate;
@@ -101,7 +101,10 @@ static int shutdown_write(struct max31827_state *st, unsigned int reg,
 	mutex_lock(&st->lock);
 
 	if (!st->enable) {
-		ret = regmap_write(st->regmap, reg, val);
+		if (!mask)
+			ret = regmap_write(st->regmap, reg, val);
+		else
+			ret = regmap_update_bits(st->regmap, reg, mask, val);
 		goto unlock;
 	}
 
@@ -116,7 +119,11 @@ static int shutdown_write(struct max31827_state *st, unsigned int reg,
 	if (ret)
 		goto unlock;
 
-	ret = regmap_write(st->regmap, reg, val);
+	if (!mask)
+		ret = regmap_write(st->regmap, reg, val);
+	else
+		ret = regmap_update_bits(st->regmap, reg, mask, val);
+
 	if (ret)
 		goto unlock;
 
@@ -134,7 +141,7 @@ static int write_alarm_val(struct max31827_state *st, unsigned int reg,
 {
 	val = MAX31827_M_DGR_TO_16_BIT(val);
 
-	return shutdown_write(st, reg, val);
+	return shutdown_write(st, reg, 0, val);
 }
 
 static umode_t max31827_is_visible(const void *state,
-- 
2.34.1

[PATCH v5 4/4] hwmon: max31827: Add custom attribute for resolution

[Daniel Matyas]

Added custom channel-specific (temp1) attribute for resolution. The wait
time for a conversion in one-shot mode (enable = 0) depends on the
resolution.

When resolution is 12-bit, the conversion time is 140ms, but the minimum
update_interval is 125ms. Handled this problem by waiting an additional
15ms (125ms + 15ms = 140ms).

Added 'mask' parameter to the shutdown_write() function. Now it can
either write or update bits, depending on the value of mask. This is
needed, because for alarms a write is necessary, but for resolution only
the resolution bits should be updated.

Signed-off-by: Daniel Matyas <daniel.matyas@analog.com>
---

v4 -> v5: No change.

v3 -> v4: No change.

v2 -> v3: Fixed indentation problems in .rst.

v1 -> v2: Changed subject. Separated patch. Removed timeout sysfs
attribute and kept only resolution. Added temp1_ prefix to resolution.
Changed value of resolution from bits to milli-degrees Celsius. Added
appropriate documentation.


 Documentation/hwmon/max31827.rst |  29 ++++++--
 drivers/hwmon/max31827.c         | 121 ++++++++++++++++++++++++++++---
 2 files changed, 134 insertions(+), 16 deletions(-)

diff --git a/Documentation/hwmon/max31827.rst b/Documentation/hwmon/max31827.rst
index a8bbfb85dd02..44ab9dc064cb 100644
--- a/Documentation/hwmon/max31827.rst
+++ b/Documentation/hwmon/max31827.rst
@@ -90,11 +90,28 @@ the data sheet are:
 
 Enabling the device when it is already enabled has the side effect of setting
 the conversion frequency to 1 conv/s. The conversion time varies depending on
-the resolution. The conversion time doubles with every bit of increased
-resolution. For 10 bit resolution 35ms are needed, while for 12 bit resolution
-(default) 140ms. When chip is in shutdown mode and a read operation is
-requested, one-shot is triggered, the device waits for 140 (conversion time) ms,
-and only after that is the temperature value register read.
+the resolution.
+
+The conversion time doubles with every bit of increased resolution. The
+available resolutions are:
+
+- 8 bit -> 8.75 ms conversion time
+- 9 bit -> 17.5 ms conversion time
+- 10 bit -> 35 ms conversion time
+- 12 bit (default) -> 140 ms conversion time
+
+There is a temp1_resolution attribute which indicates the unit change in the
+input temperature in milli-degrees C.
+
+- 1000 mC -> 8 bit
+- 500 mC -> 9 bit
+- 250 mC -> 10 bit
+- 62 mC -> 12 bit (default) - actually this is 62.5, but the fil returns 62
+
+When chip is in shutdown mode and a read operation is requested, one-shot is
+triggered, the device waits for <conversion time> ms, and only after that is
+the temperature value register read. Note that the conversion times are rounded
+up to the nearest possible integer.
 
 The LSB of the temperature values is 0.0625 degrees Celsius, but the values of
 the temperatures are displayed in milli-degrees. This means, that some data is
@@ -117,4 +134,4 @@ corresponding status bits.
 Notes
 -----
 
-PEC and resolution are not implemented.
+PEC is not implemented.
diff --git a/drivers/hwmon/max31827.c b/drivers/hwmon/max31827.c
index 8ba387b51157..c9fa6d4d6194 100644
--- a/drivers/hwmon/max31827.c
+++ b/drivers/hwmon/max31827.c
@@ -37,6 +37,9 @@
 #define MAX31827_CONFIGURATION_U_TEMP_STAT_MASK	BIT(14)
 #define MAX31827_CONFIGURATION_O_TEMP_STAT_MASK	BIT(15)
 
+#define MAX31827_8_BIT_CNV_TIME		9
+#define MAX31827_9_BIT_CNV_TIME		18
+#define MAX31827_10_BIT_CNV_TIME	35
 #define MAX31827_12_BIT_CNV_TIME	140
 
 #define MAX31827_ALRM_POL_HIGH	0x1
@@ -68,6 +71,27 @@ static const u16 max31827_conversions[] = {
 	[MAX31827_CNV_8_HZ] = 125,
 };
 
+enum max31827_resolution {
+	MAX31827_RES_8_BIT = 0,
+	MAX31827_RES_9_BIT,
+	MAX31827_RES_10_BIT,
+	MAX31827_RES_12_BIT,
+};
+
+static const u16 max31827_resolutions[] = {
+	[MAX31827_RES_8_BIT] = 1000,
+	[MAX31827_RES_9_BIT] = 500,
+	[MAX31827_RES_10_BIT] = 250,
+	[MAX31827_RES_12_BIT] = 62,
+};
+
+static const u16 max31827_conv_times[] = {
+	[MAX31827_RES_8_BIT] = MAX31827_8_BIT_CNV_TIME,
+	[MAX31827_RES_9_BIT] = MAX31827_9_BIT_CNV_TIME,
+	[MAX31827_RES_10_BIT] = MAX31827_10_BIT_CNV_TIME,
+	[MAX31827_RES_12_BIT] = MAX31827_12_BIT_CNV_TIME,
+};
+
 struct max31827_state {
 	/*
 	 * Prevent simultaneous access to the i2c client.
@@ -75,6 +99,8 @@ struct max31827_state {
 	struct mutex lock;
 	struct regmap *regmap;
 	bool enable;
+	unsigned int resolution;
+	unsigned int update_interval;
 };
 
 static const struct regmap_config max31827_regmap = {
@@ -91,9 +117,9 @@ static int shutdown_write(struct max31827_state *st, unsigned int reg,
 	int ret;
 
 	/*
-	 * Before the Temperature Threshold Alarm and Alarm Hysteresis Threshold
-	 * register values are changed over I2C, the part must be in shutdown
-	 * mode.
+	 * Before the Temperature Threshold Alarm, Alarm Hysteresis Threshold
+	 * and Resolution bits from Configuration register are changed over I2C,
+	 * the part must be in shutdown mode.
 	 *
 	 * Mutex is used to ensure, that some other process doesn't change the
 	 * configuration register.
@@ -211,9 +237,18 @@ static int max31827_read(struct device *dev, enum hwmon_sensor_types type,
 					mutex_unlock(&st->lock);
 					return ret;
 				}
-
-				msleep(MAX31827_12_BIT_CNV_TIME);
+				msleep(max31827_conv_times[st->resolution]);
 			}
+
+			/*
+			 * For 12-bit resolution the conversion time is 140 ms,
+			 * thus an additional 15 ms is needed to complete the
+			 * conversion: 125 ms + 15 ms = 140 ms
+			 */
+			if (max31827_resolutions[st->resolution] == 12 &&
+			    st->update_interval == 125)
+				usleep_range(15000, 20000);
+
 			ret = regmap_read(st->regmap, MAX31827_T_REG, &uval);
 
 			mutex_unlock(&st->lock);
@@ -371,10 +406,14 @@ static int max31827_write(struct device *dev, enum hwmon_sensor_types type,
 			res = FIELD_PREP(MAX31827_CONFIGURATION_CNV_RATE_MASK,
 					 res);
 
-			return regmap_update_bits(st->regmap,
-						  MAX31827_CONFIGURATION_REG,
-						  MAX31827_CONFIGURATION_CNV_RATE_MASK,
-						  res);
+			ret = regmap_update_bits(st->regmap,
+						 MAX31827_CONFIGURATION_REG,
+						 MAX31827_CONFIGURATION_CNV_RATE_MASK,
+						 res);
+			if (ret)
+				return ret;
+
+			st->update_interval = val;
 		}
 		break;
 
@@ -385,6 +424,68 @@ static int max31827_write(struct device *dev, enum hwmon_sensor_types type,
 	return -EOPNOTSUPP;
 }
 
+static ssize_t temp1_resolution_show(struct device *dev,
+				     struct device_attribute *devattr,
+				     char *buf)
+{
+	struct max31827_state *st = dev_get_drvdata(dev);
+	unsigned int val;
+	int ret;
+
+	ret = regmap_read(st->regmap, MAX31827_CONFIGURATION_REG, &val);
+	if (ret)
+		return ret;
+
+	val = FIELD_GET(MAX31827_CONFIGURATION_RESOLUTION_MASK, val);
+
+	return scnprintf(buf, PAGE_SIZE, "%u\n", max31827_resolutions[val]);
+}
+
+static ssize_t temp1_resolution_store(struct device *dev,
+				      struct device_attribute *devattr,
+				      const char *buf, size_t count)
+{
+	struct max31827_state *st = dev_get_drvdata(dev);
+	unsigned int idx = 0;
+	unsigned int val;
+	int ret;
+
+	ret = kstrtouint(buf, 10, &val);
+	if (ret)
+		return ret;
+
+	/*
+	 * Convert the desired resolution into register
+	 * bits. idx is already initialized with 0.
+	 *
+	 * This was inspired by lm73 driver.
+	 */
+	while (idx < ARRAY_SIZE(max31827_resolutions) &&
+	       val < max31827_resolutions[idx])
+		idx++;
+
+	if (idx == ARRAY_SIZE(max31827_resolutions) ||
+	    val != max31827_resolutions[idx])
+		return -EOPNOTSUPP;
+
+	st->resolution = idx;
+
+	ret = shutdown_write(st, MAX31827_CONFIGURATION_REG,
+			     MAX31827_CONFIGURATION_RESOLUTION_MASK,
+			     FIELD_PREP(MAX31827_CONFIGURATION_RESOLUTION_MASK,
+					idx));
+
+	return (ret) ? ret : count;
+}
+
+static DEVICE_ATTR_RW(temp1_resolution);
+
+static struct attribute *max31827_attrs[] = {
+	&dev_attr_temp1_resolution.attr,
+	NULL
+};
+ATTRIBUTE_GROUPS(max31827);
+
 static const struct i2c_device_id max31827_i2c_ids[] = {
 	{ "max31827", max31827 },
 	{ "max31828", max31828 },
@@ -501,7 +602,7 @@ static int max31827_probe(struct i2c_client *client)
 
 	hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name, st,
 							 &max31827_chip_info,
-							 NULL);
+							 max31827_groups);
 
 	return PTR_ERR_OR_ZERO(hwmon_dev);
 }
-- 
2.34.1

Re: [PATCH v5 4/4] hwmon: max31827: Add custom attribute for resolution

[Guenter Roeck]

On 10/26/23 07:44, Daniel Matyas wrote:
> Added custom channel-specific (temp1) attribute for resolution. The wait
> time for a conversion in one-shot mode (enable = 0) depends on the
> resolution.
> 
> When resolution is 12-bit, the conversion time is 140ms, but the minimum
> update_interval is 125ms. Handled this problem by waiting an additional
> 15ms (125ms + 15ms = 140ms).
> 
> Added 'mask' parameter to the shutdown_write() function. Now it can
> either write or update bits, depending on the value of mask. This is
> needed, because for alarms a write is necessary, but for resolution only
> the resolution bits should be updated.
> 
> Signed-off-by: Daniel Matyas <daniel.matyas@analog.com>
> ---
> 
> v4 -> v5: No change.
> 
> v3 -> v4: No change.
> 
> v2 -> v3: Fixed indentation problems in .rst.
> 
> v1 -> v2: Changed subject. Separated patch. Removed timeout sysfs
> attribute and kept only resolution. Added temp1_ prefix to resolution.
> Changed value of resolution from bits to milli-degrees Celsius. Added
> appropriate documentation.
> 
> 
>   Documentation/hwmon/max31827.rst |  29 ++++++--
>   drivers/hwmon/max31827.c         | 121 ++++++++++++++++++++++++++++---
>   2 files changed, 134 insertions(+), 16 deletions(-)
> 
> diff --git a/Documentation/hwmon/max31827.rst b/Documentation/hwmon/max31827.rst
> index a8bbfb85dd02..44ab9dc064cb 100644
> --- a/Documentation/hwmon/max31827.rst
> +++ b/Documentation/hwmon/max31827.rst
> @@ -90,11 +90,28 @@ the data sheet are:
>   
>   Enabling the device when it is already enabled has the side effect of setting
>   the conversion frequency to 1 conv/s. The conversion time varies depending on
> -the resolution. The conversion time doubles with every bit of increased
> -resolution. For 10 bit resolution 35ms are needed, while for 12 bit resolution
> -(default) 140ms. When chip is in shutdown mode and a read operation is
> -requested, one-shot is triggered, the device waits for 140 (conversion time) ms,
> -and only after that is the temperature value register read.
> +the resolution.
> +
> +The conversion time doubles with every bit of increased resolution. The
> +available resolutions are:
> +
> +- 8 bit -> 8.75 ms conversion time
> +- 9 bit -> 17.5 ms conversion time
> +- 10 bit -> 35 ms conversion time
> +- 12 bit (default) -> 140 ms conversion time
> +
> +There is a temp1_resolution attribute which indicates the unit change in the
> +input temperature in milli-degrees C.
> +
> +- 1000 mC -> 8 bit
> +- 500 mC -> 9 bit
> +- 250 mC -> 10 bit
> +- 62 mC -> 12 bit (default) - actually this is 62.5, but the fil returns 62

fil ? Should that be "attribute" ?

> +
> +When chip is in shutdown mode and a read operation is requested, one-shot is
> +triggered, the device waits for <conversion time> ms, and only after that is
> +the temperature value register read. Note that the conversion times are rounded
> +up to the nearest possible integer.
>   
>   The LSB of the temperature values is 0.0625 degrees Celsius, but the values of
>   the temperatures are displayed in milli-degrees. This means, that some data is
> @@ -117,4 +134,4 @@ corresponding status bits.
>   Notes
>   -----
>   
> -PEC and resolution are not implemented.
> +PEC is not implemented.
> diff --git a/drivers/hwmon/max31827.c b/drivers/hwmon/max31827.c
> index 8ba387b51157..c9fa6d4d6194 100644
> --- a/drivers/hwmon/max31827.c
> +++ b/drivers/hwmon/max31827.c
> @@ -37,6 +37,9 @@
>   #define MAX31827_CONFIGURATION_U_TEMP_STAT_MASK	BIT(14)
>   #define MAX31827_CONFIGURATION_O_TEMP_STAT_MASK	BIT(15)
>   
> +#define MAX31827_8_BIT_CNV_TIME		9
> +#define MAX31827_9_BIT_CNV_TIME		18
> +#define MAX31827_10_BIT_CNV_TIME	35
>   #define MAX31827_12_BIT_CNV_TIME	140
>   
>   #define MAX31827_ALRM_POL_HIGH	0x1
> @@ -68,6 +71,27 @@ static const u16 max31827_conversions[] = {
>   	[MAX31827_CNV_8_HZ] = 125,
>   };
>   
> +enum max31827_resolution {
> +	MAX31827_RES_8_BIT = 0,
> +	MAX31827_RES_9_BIT,
> +	MAX31827_RES_10_BIT,
> +	MAX31827_RES_12_BIT,
> +};
> +
> +static const u16 max31827_resolutions[] = {
> +	[MAX31827_RES_8_BIT] = 1000,
> +	[MAX31827_RES_9_BIT] = 500,
> +	[MAX31827_RES_10_BIT] = 250,
> +	[MAX31827_RES_12_BIT] = 62,
> +};
> +
> +static const u16 max31827_conv_times[] = {
> +	[MAX31827_RES_8_BIT] = MAX31827_8_BIT_CNV_TIME,
> +	[MAX31827_RES_9_BIT] = MAX31827_9_BIT_CNV_TIME,
> +	[MAX31827_RES_10_BIT] = MAX31827_10_BIT_CNV_TIME,
> +	[MAX31827_RES_12_BIT] = MAX31827_12_BIT_CNV_TIME,
> +};
> +
>   struct max31827_state {
>   	/*
>   	 * Prevent simultaneous access to the i2c client.
> @@ -75,6 +99,8 @@ struct max31827_state {
>   	struct mutex lock;
>   	struct regmap *regmap;
>   	bool enable;
> +	unsigned int resolution;
> +	unsigned int update_interval;
>   };
>   
>   static const struct regmap_config max31827_regmap = {
> @@ -91,9 +117,9 @@ static int shutdown_write(struct max31827_state *st, unsigned int reg,
>   	int ret;
>   
>   	/*
> -	 * Before the Temperature Threshold Alarm and Alarm Hysteresis Threshold
> -	 * register values are changed over I2C, the part must be in shutdown
> -	 * mode.
> +	 * Before the Temperature Threshold Alarm, Alarm Hysteresis Threshold
> +	 * and Resolution bits from Configuration register are changed over I2C,
> +	 * the part must be in shutdown mode.
>   	 *
>   	 * Mutex is used to ensure, that some other process doesn't change the
>   	 * configuration register.
> @@ -211,9 +237,18 @@ static int max31827_read(struct device *dev, enum hwmon_sensor_types type,
>   					mutex_unlock(&st->lock);
>   					return ret;
>   				}
> -
> -				msleep(MAX31827_12_BIT_CNV_TIME);
> +				msleep(max31827_conv_times[st->resolution]);
>   			}
> +
> +			/*
> +			 * For 12-bit resolution the conversion time is 140 ms,
> +			 * thus an additional 15 ms is needed to complete the
> +			 * conversion: 125 ms + 15 ms = 140 ms
> +			 */
> +			if (max31827_resolutions[st->resolution] == 12 &&
> +			    st->update_interval == 125)
> +				usleep_range(15000, 20000);
> +
>   			ret = regmap_read(st->regmap, MAX31827_T_REG, &uval);
>   
>   			mutex_unlock(&st->lock);
> @@ -371,10 +406,14 @@ static int max31827_write(struct device *dev, enum hwmon_sensor_types type,
>   			res = FIELD_PREP(MAX31827_CONFIGURATION_CNV_RATE_MASK,
>   					 res);
>   
> -			return regmap_update_bits(st->regmap,
> -						  MAX31827_CONFIGURATION_REG,
> -						  MAX31827_CONFIGURATION_CNV_RATE_MASK,
> -						  res);
> +			ret = regmap_update_bits(st->regmap,
> +						 MAX31827_CONFIGURATION_REG,
> +						 MAX31827_CONFIGURATION_CNV_RATE_MASK,
> +						 res);
> +			if (ret)
> +				return ret;
> +
> +			st->update_interval = val;
>   		}
>   		break;
>   
> @@ -385,6 +424,68 @@ static int max31827_write(struct device *dev, enum hwmon_sensor_types type,
>   	return -EOPNOTSUPP;
>   }
>   
> +static ssize_t temp1_resolution_show(struct device *dev,
> +				     struct device_attribute *devattr,
> +				     char *buf)
> +{
> +	struct max31827_state *st = dev_get_drvdata(dev);
> +	unsigned int val;
> +	int ret;
> +
> +	ret = regmap_read(st->regmap, MAX31827_CONFIGURATION_REG, &val);
> +	if (ret)
> +		return ret;
> +
> +	val = FIELD_GET(MAX31827_CONFIGURATION_RESOLUTION_MASK, val);
> +
> +	return scnprintf(buf, PAGE_SIZE, "%u\n", max31827_resolutions[val]);
> +}
> +
> +static ssize_t temp1_resolution_store(struct device *dev,
> +				      struct device_attribute *devattr,
> +				      const char *buf, size_t count)
> +{
> +	struct max31827_state *st = dev_get_drvdata(dev);
> +	unsigned int idx = 0;
> +	unsigned int val;
> +	int ret;
> +
> +	ret = kstrtouint(buf, 10, &val);
> +	if (ret)
> +		return ret;
> +
> +	/*
> +	 * Convert the desired resolution into register
> +	 * bits. idx is already initialized with 0.
> +	 *
> +	 * This was inspired by lm73 driver.
> +	 */
> +	while (idx < ARRAY_SIZE(max31827_resolutions) &&
> +	       val < max31827_resolutions[idx])
> +		idx++;
> +
> +	if (idx == ARRAY_SIZE(max31827_resolutions) ||
> +	    val != max31827_resolutions[idx])
> +		return -EOPNOTSUPP;

		-EINVAL

Question here is if this should return the closest value/index
or return an error. Traditionally, for ranges like this, drivers
would accept all values and select the closest supported value.
[ just as the lm73 driver, which is listed as example here, does ]
There are even helper functions for that - find_closest()
or find_closest_descending(). I would very much prefer the
more flexible approach and not burden the user with having to find
supported values.

> +
> +	st->resolution = idx;
> +
> +	ret = shutdown_write(st, MAX31827_CONFIGURATION_REG,
> +			     MAX31827_CONFIGURATION_RESOLUTION_MASK,
> +			     FIELD_PREP(MAX31827_CONFIGURATION_RESOLUTION_MASK,
> +					idx));
> +
> +	return (ret) ? ret : count;

drop () around ret

> +}
> +
> +static DEVICE_ATTR_RW(temp1_resolution);
> +
> +static struct attribute *max31827_attrs[] = {
> +	&dev_attr_temp1_resolution.attr,
> +	NULL
> +};
> +ATTRIBUTE_GROUPS(max31827);
> +
>   static const struct i2c_device_id max31827_i2c_ids[] = {
>   	{ "max31827", max31827 },
>   	{ "max31828", max31828 },
> @@ -501,7 +602,7 @@ static int max31827_probe(struct i2c_client *client)
>   
>   	hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name, st,
>   							 &max31827_chip_info,
> -							 NULL);
> +							 max31827_groups);
>   
>   	return PTR_ERR_OR_ZERO(hwmon_dev);
>   }