[PATCH 4/4] hwmon: max31827: Add custom attribute for resolution
From: Daniel Matyas
Date: Wed Sep 13 2023 - 11:25:57 EST
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).
Signed-off-by: Daniel Matyas <daniel.matyas@xxxxxxxxxx>
---
Documentation/hwmon/max31827.rst | 28 +++++--
drivers/hwmon/max31827.c | 136 +++++++++++++++++++++++++++----
2 files changed, 144 insertions(+), 20 deletions(-)
diff --git a/Documentation/hwmon/max31827.rst b/Documentation/hwmon/max31827.rst
index e0eca1eb5c06..219ab8abfd6a 100644
--- a/Documentation/hwmon/max31827.rst
+++ b/Documentation/hwmon/max31827.rst
@@ -89,11 +89,27 @@ 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 file
+ 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
@@ -116,4 +132,4 @@ 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 4dc14642775a..396292c0bc32 100644
--- a/drivers/hwmon/max31827.c
+++ b/drivers/hwmon/max31827.c
@@ -43,6 +43,9 @@
#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_FLT_Q_1 0x0
@@ -51,6 +54,7 @@
#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)
+#define MAX31827_FLT_Q
enum chips { max31827, max31828, max31829 };
@@ -74,6 +78,27 @@ 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.
@@ -81,6 +106,8 @@ struct max31827_state {
struct mutex lock;
struct regmap *regmap;
bool enable;
+ unsigned int resolution;
+ unsigned int update_interval;
struct i2c_client *client;
};
@@ -98,9 +125,9 @@ 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 +238,18 @@ 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 +407,14 @@ 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;
@@ -385,11 +425,79 @@ 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, cfg;
+ int ret;
+
+ ret = kstrtouint(buf, 10, &val);
+ if (ret)
+ return ret;
+
+ /*
+ * Convert the desired conversion rate into register
+ * bits. idx is already initialized with 1.
+ *
+ * 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 = regmap_read(st->regmap, MAX31827_CONFIGURATION_REG, &cfg);
+ if (ret)
+ return ret;
+
+ cfg = (cfg & ~MAX31827_CONFIGURATION_RESOLUTION_MASK) |
+ FIELD_PREP(MAX31827_CONFIGURATION_RESOLUTION_MASK, idx);
+ cfg &= ~(MAX31827_CONFIGURATION_CNV_RATE_MASK |
+ MAX31827_CONFIGURATION_1SHOT_MASK);
+
+ ret = shutdown_write(st, MAX31827_CONFIGURATION_REG, cfg);
+
+ 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 },
- { "max31829", max31829 },
- { }
+ { "max31827", max31827 },
+ { "max31828", max31828 },
+ { "max31829", max31829 },
+ { }
};
MODULE_DEVICE_TABLE(i2c, max31827_i2c_ids);
@@ -525,7 +633,7 @@ 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