[PATCH v6 1/5] hwmon: max31827: Handle new properties from the devicetree

[PATCH v6 1/5] 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>
---

v5 -> v6: Added back default value for adi,fault-q and adi,alarm-pol.
Converting adi,fault-q from devicetree to register bits is cleaner.

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         | 75 +++++++++++++++++++++++++++++---
 2 files changed, 108 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..bc201a8fcd5b 100644
--- a/drivers/hwmon/max31827.c
+++ b/drivers/hwmon/max31827.c
@@ -12,6 +12,7 @@
 #include <linux/i2c.h>
 #include <linux/mutex.h>
 #include <linux/regmap.h>
+#include <linux/of_device.h>
 
 #define MAX31827_T_REG			0x0
 #define MAX31827_CONFIGURATION_REG	0x2
@@ -22,9 +23,17 @@
 
 #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)
 
+#define MAX31827_ALRM_POL_LOW	0x0
+#define MAX31827_FLT_Q_1	0x0
+
 #define MAX31827_12_BIT_CNV_TIME	140
 
 #define MAX31827_16_BIT_TO_M_DGR(x)	(sign_extend32(x, 15) * 1000 / 16)
@@ -361,14 +370,68 @@ 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);
+	} else {
+		/*
+		 * Set default value.
+		 */
+		res |= FIELD_PREP(MAX31827_CONFIGURATION_ALRM_POL_MASK,
+				  MAX31827_ALRM_POL_LOW);
+	}
+
+	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.
+		 */
+		if (data != 0)
+			lsb_idx = __ffs(data);
+
+		if (hweight32(data) != 1 || lsb_idx > 4) {
+			dev_err(dev, "Invalid data in adi,fault-q\n");
+			return -EINVAL;
+		}
+
+		res |= FIELD_PREP(MAX31827_CONFIGURATION_FLT_Q_MASK, lsb_idx);
+	} else {
+		/*
+		 * Set default value.
+		 */
+		res |= FIELD_PREP(MAX31827_CONFIGURATION_FLT_Q_MASK,
+				  MAX31827_FLT_Q_1);
+	}
 
-	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 +475,7 @@ 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 v6 2/5] hwmon: max31827: Add support for max31828 and max31829

[Daniel Matyas]

Created of_match_table and id_table entries for max31828 and max31829.

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

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

v5 -> v6: Selecting default value for adi,fault-q and adi,alarm-pol with
switch() statement. Used device_get_match_data() to get data more
generally. Now max31827 = 1 in enum.

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 | 64 +++++++++++++++++++++++++++++++++-------
 1 file changed, 53 insertions(+), 11 deletions(-)

diff --git a/drivers/hwmon/max31827.c b/drivers/hwmon/max31827.c
index bc201a8fcd5b..738ce5ca6e39 100644
--- a/drivers/hwmon/max31827.c
+++ b/drivers/hwmon/max31827.c
@@ -32,7 +32,9 @@
 #define MAX31827_CONFIGURATION_O_TEMP_STAT_MASK	BIT(15)
 
 #define MAX31827_ALRM_POL_LOW	0x0
+#define MAX31827_ALRM_POL_HIGH	0x1
 #define MAX31827_FLT_Q_1	0x0
+#define MAX31827_FLT_Q_4	0x2
 
 #define MAX31827_12_BIT_CNV_TIME	140
 
@@ -40,6 +42,8 @@
 #define MAX31827_M_DGR_TO_16_BIT(x)	(((x) << 4) / 1000)
 #define MAX31827_DEVICE_ENABLE(x)	((x) ? 0xA : 0x0)
 
+enum chips { max31827 = 1, max31828, max31829 };
+
 enum max31827_cnv {
 	MAX31827_CNV_1_DIV_64_HZ = 1,
 	MAX31827_CNV_1_DIV_32_HZ,
@@ -370,12 +374,21 @@ 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 fwnode_handle *fwnode;
 	unsigned int res = 0;
 	u32 data, lsb_idx;
+	enum chips type;
 	bool prop;
 	int ret;
 
@@ -392,6 +405,8 @@ 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);
 
+	type = (enum chips)(uintptr_t)device_get_match_data(dev);
+
 	if (fwnode_property_present(fwnode, "adi,alarm-pol")) {
 		ret = fwnode_property_read_u32(fwnode, "adi,alarm-pol", &data);
 		if (ret)
@@ -402,8 +417,19 @@ static int max31827_init_client(struct max31827_state *st,
 		/*
 		 * Set default value.
 		 */
-		res |= FIELD_PREP(MAX31827_CONFIGURATION_ALRM_POL_MASK,
-				  MAX31827_ALRM_POL_LOW);
+		switch (type) {
+		case max31827:
+		case max31828:
+			res |= FIELD_PREP(MAX31827_CONFIGURATION_ALRM_POL_MASK,
+					  MAX31827_ALRM_POL_LOW);
+			break;
+		case max31829:
+			res |= FIELD_PREP(MAX31827_CONFIGURATION_ALRM_POL_MASK,
+					  MAX31827_ALRM_POL_HIGH);
+			break;
+		default:
+			return -EOPNOTSUPP;
+		}
 	}
 
 	if (fwnode_property_present(fwnode, "adi,fault-q")) {
@@ -427,8 +453,19 @@ static int max31827_init_client(struct max31827_state *st,
 		/*
 		 * Set default value.
 		 */
-		res |= FIELD_PREP(MAX31827_CONFIGURATION_FLT_Q_MASK,
-				  MAX31827_FLT_Q_1);
+		switch (type) {
+		case max31827:
+			res |= FIELD_PREP(MAX31827_CONFIGURATION_FLT_Q_MASK,
+					  MAX31827_FLT_Q_1);
+			break;
+		case max31828:
+		case max31829:
+			res |= FIELD_PREP(MAX31827_CONFIGURATION_FLT_Q_MASK,
+					  MAX31827_FLT_Q_4);
+			break;
+		default:
+			return -EOPNOTSUPP;
+		}
 	}
 
 	return regmap_write(st->regmap, MAX31827_CONFIGURATION_REG, res);
@@ -486,14 +523,19 @@ 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 v6 3/5] 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 -> v6: 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 738ce5ca6e39..41e4f716605a 100644
--- a/drivers/hwmon/max31827.c
+++ b/drivers/hwmon/max31827.c
@@ -80,7 +80,7 @@ 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;
@@ -97,7 +97,10 @@ 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;
 	}
 
@@ -112,7 +115,11 @@ 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;
 
@@ -130,7 +137,7 @@ 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 v6 4/5] hwmon: max31827: Return closest value in update_interval

[Daniel Matyas]

When user writes a value to update_interval which does not match the
possible values, instead of returning invalid error, return the closest
value.

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

v6: Added patch.

 drivers/hwmon/max31827.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/hwmon/max31827.c b/drivers/hwmon/max31827.c
index 41e4f716605a..13ebe691475a 100644
--- a/drivers/hwmon/max31827.c
+++ b/drivers/hwmon/max31827.c
@@ -360,9 +360,8 @@ static int max31827_write(struct device *dev, enum hwmon_sensor_types type,
 			       val < max31827_conversions[res])
 				res++;
 
-			if (res == ARRAY_SIZE(max31827_conversions) ||
-			    val != max31827_conversions[res])
-				return -EINVAL;
+			if (res == ARRAY_SIZE(max31827_conversions))
+				res = ARRAY_SIZE(max31827_conversions) - 1;
 
 			res = FIELD_PREP(MAX31827_CONFIGURATION_CNV_RATE_MASK,
 					 res);
-- 
2.34.1

[PATCH v6 5/5] 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>
---

v5 -> v6: Resolution selects value closest to input value.

v3 -> v5: 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         | 122 ++++++++++++++++++++++++++++---
 2 files changed, 134 insertions(+), 17 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 13ebe691475a..ea10b4a0fcab 100644
--- a/drivers/hwmon/max31827.c
+++ b/drivers/hwmon/max31827.c
@@ -36,6 +36,9 @@
 #define MAX31827_FLT_Q_1	0x0
 #define MAX31827_FLT_Q_4	0x2
 
+#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_16_BIT_TO_M_DGR(x)	(sign_extend32(x, 15) * 1000 / 16)
@@ -64,6 +67,27 @@ 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.
@@ -71,6 +95,8 @@ 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 = {
@@ -87,9 +113,9 @@ 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.
@@ -207,9 +233,18 @@ 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);
@@ -366,10 +401,14 @@ 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;
 
@@ -377,9 +416,70 @@ static int max31827_write(struct device *dev, enum hwmon_sensor_types type,
 		return -EOPNOTSUPP;
 	}
 
-	return -EOPNOTSUPP;
+	return 0;
+}
+
+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))
+		idx = ARRAY_SIZE(max31827_resolutions) - 1;
+
+	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 },
@@ -524,7 +624,7 @@ 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 v6 5/5] hwmon: max31827: Add custom attribute for resolution

[Guenter Roeck]

On Tue, Oct 31, 2023 at 08:21:57PM +0200, 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>

Series applied.

Thanks,
Guenter