[PATCH 2/2] hwmon: max31827: Functional enhancement of the driver
From: Daniel Matyas
Date: Mon Sep 11 2023 - 18:43:48 EST
Modify some bits depending on the device tree.
Added custom device attributes for resolution and timeout. The wait time
for a conversion in one-shot mode (enable = 0) depends on the
resolution.
Used enums and static const arrays in order to remove nested switch
blocks.
Signed-off-by: Daniel Matyas <daniel.matyas@xxxxxxxxxx>
---
Documentation/hwmon/max31827.rst | 65 ++++--
drivers/hwmon/max31827.c | 326 ++++++++++++++++++++++++-------
2 files changed, 306 insertions(+), 85 deletions(-)
diff --git a/Documentation/hwmon/max31827.rst b/Documentation/hwmon/max31827.rst
index b0971d05b8a4..ae884e9e6085 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
@@ -68,13 +76,32 @@ 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
-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) + 1
-(error) 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
+
+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
@@ -83,8 +110,18 @@ 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 is not implemented.
diff --git a/drivers/hwmon/max31827.c b/drivers/hwmon/max31827.c
index 66f5fcf937ff..9f48dec99b7f 100644
--- a/drivers/hwmon/max31827.c
+++ b/drivers/hwmon/max31827.c
@@ -12,6 +12,18 @@
#include <linux/i2c.h>
#include <linux/mutex.h>
#include <linux/regmap.h>
+#include <linux/hwmon-sysfs.h>
+
+/*
+ * gcc turns __builtin_ffsll() into a call to __ffsdi2(), which is not provided
+ * by every architecture. __ffs64() is available on all architectures, but the
+ * result is not defined if no bits are set.
+ */
+#define max31827__bf_shf(x) \
+ ({ \
+ typeof(x) x_ = (x); \
+ ((x_) != 0) ? __ffs64(x_) : 0x0; \
+ })
#define MAX31827_T_REG 0x0
#define MAX31827_CONFIGURATION_REG 0x2
@@ -22,22 +34,120 @@
#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_12_BIT_CNV_TIME 141
-
-#define MAX31827_CNV_1_DIV_64_HZ 0x1
-#define MAX31827_CNV_1_DIV_32_HZ 0x2
-#define MAX31827_CNV_1_DIV_16_HZ 0x3
-#define MAX31827_CNV_1_DIV_4_HZ 0x4
-#define MAX31827_CNV_1_HZ 0x5
-#define MAX31827_CNV_4_HZ 0x6
-#define MAX31827_CNV_8_HZ 0x7
+#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)
#define MAX31827_M_DGR_TO_16_BIT(x) (((x) << 4) / 1000)
#define MAX31827_DEVICE_ENABLE(x) ((x) ? 0xA : 0x0)
+#define MAX31827_FLT_Q
+
+enum max31827_cnv {
+ MAX31827_CNV_1_DIV_64_HZ = 1,
+ MAX31827_CNV_1_DIV_32_HZ,
+ MAX31827_CNV_1_DIV_16_HZ,
+ MAX31827_CNV_1_DIV_4_HZ,
+ MAX31827_CNV_1_HZ,
+ MAX31827_CNV_4_HZ,
+ MAX31827_CNV_8_HZ,
+};
+
+static const u16 max31827_conversions[] = {
+ [MAX31827_CNV_1_DIV_64_HZ] = 64000,
+ [MAX31827_CNV_1_DIV_32_HZ] = 32000,
+ [MAX31827_CNV_1_DIV_16_HZ] = 16000,
+ [MAX31827_CNV_1_DIV_4_HZ] = 4000,
+ [MAX31827_CNV_1_HZ] = 1000,
+ [MAX31827_CNV_4_HZ] = 250,
+ [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] = 8,
+ [MAX31827_RES_9_BIT] = 9,
+ [MAX31827_RES_10_BIT] = 10,
+ [MAX31827_RES_12_BIT] = 12,
+};
+
+enum cfg_index {
+ cfg_timeout_idx = 0,
+ cfg_res_idx,
+ cfg_num
+};
+
+static const unsigned int cfg_masks[cfg_num] = {
+ [cfg_timeout_idx] = MAX31827_CONFIGURATION_TIMEOUT_MASK,
+ [cfg_res_idx] = MAX31827_CONFIGURATION_RESOLUTION_MASK,
+};
+
+enum max31827_cnv {
+ MAX31827_CNV_1_DIV_64_HZ = 1,
+ MAX31827_CNV_1_DIV_32_HZ,
+ MAX31827_CNV_1_DIV_16_HZ,
+ MAX31827_CNV_1_DIV_4_HZ,
+ MAX31827_CNV_1_HZ,
+ MAX31827_CNV_4_HZ,
+ MAX31827_CNV_8_HZ,
+};
+
+static const u16 max31827_conversions[] = {
+ [MAX31827_CNV_1_DIV_64_HZ] = 64000,
+ [MAX31827_CNV_1_DIV_32_HZ] = 32000,
+ [MAX31827_CNV_1_DIV_16_HZ] = 16000,
+ [MAX31827_CNV_1_DIV_4_HZ] = 4000,
+ [MAX31827_CNV_1_HZ] = 1000,
+ [MAX31827_CNV_4_HZ] = 250,
+ [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] = 8,
+ [MAX31827_RES_9_BIT] = 9,
+ [MAX31827_RES_10_BIT] = 10,
+ [MAX31827_RES_12_BIT] = 12,
+};
+
+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,
+};
+
+enum cfg_index {
+ cfg_timeout_idx = 0,
+ cfg_res_idx,
+ cfg_num
+};
+
+static const unsigned int cfg_masks[cfg_num] = {
+ [cfg_timeout_idx] = MAX31827_CONFIGURATION_TIMEOUT_MASK,
+ [cfg_res_idx] = MAX31827_CONFIGURATION_RESOLUTION_MASK,
+};
struct max31827_state {
/*
@@ -46,6 +156,7 @@ struct max31827_state {
struct mutex lock;
struct regmap *regmap;
bool enable;
+ unsigned int resolution;
};
static const struct regmap_config max31827_regmap = {
@@ -166,8 +277,7 @@ 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]);
}
ret = regmap_read(st->regmap, MAX31827_T_REG, &uval);
@@ -243,32 +353,7 @@ static int max31827_read(struct device *dev, enum hwmon_sensor_types type,
uval = FIELD_GET(MAX31827_CONFIGURATION_CNV_RATE_MASK,
uval);
- switch (uval) {
- case MAX31827_CNV_1_DIV_64_HZ:
- *val = 64000;
- break;
- case MAX31827_CNV_1_DIV_32_HZ:
- *val = 32000;
- break;
- case MAX31827_CNV_1_DIV_16_HZ:
- *val = 16000;
- break;
- case MAX31827_CNV_1_DIV_4_HZ:
- *val = 4000;
- break;
- case MAX31827_CNV_1_HZ:
- *val = 1000;
- break;
- case MAX31827_CNV_4_HZ:
- *val = 250;
- break;
- case MAX31827_CNV_8_HZ:
- *val = 125;
- break;
- default:
- *val = 0;
- break;
- }
+ *val = max31827_conversions[uval];
}
break;
@@ -284,6 +369,7 @@ static int max31827_write(struct device *dev, enum hwmon_sensor_types type,
u32 attr, int channel, long val)
{
struct max31827_state *st = dev_get_drvdata(dev);
+ int res = 1;
int ret;
switch (type) {
@@ -333,39 +419,27 @@ static int max31827_write(struct device *dev, enum hwmon_sensor_types type,
if (!st->enable)
return -EOPNOTSUPP;
- switch (val) {
- case 125:
- val = MAX31827_CNV_8_HZ;
- break;
- case 250:
- val = MAX31827_CNV_4_HZ;
- break;
- case 1000:
- val = MAX31827_CNV_1_HZ;
- break;
- case 4000:
- val = MAX31827_CNV_1_DIV_4_HZ;
- break;
- case 16000:
- val = MAX31827_CNV_1_DIV_16_HZ;
- break;
- case 32000:
- val = MAX31827_CNV_1_DIV_32_HZ;
- break;
- case 64000:
- val = MAX31827_CNV_1_DIV_64_HZ;
- break;
- default:
+ /*
+ * Convert the desired conversion rate into register
+ * bits. res is already initialized with 1.
+ *
+ * This was inspired by lm73 driver.
+ */
+ while (res < ARRAY_SIZE(max31827_conversions) &&
+ val < max31827_conversions[res])
+ res++;
+
+ if (res == ARRAY_SIZE(max31827_conversions) ||
+ val != max31827_conversions[res])
return -EOPNOTSUPP;
- }
- val = FIELD_PREP(MAX31827_CONFIGURATION_CNV_RATE_MASK,
- val);
+ res = FIELD_PREP(MAX31827_CONFIGURATION_CNV_RATE_MASK,
+ res);
return regmap_update_bits(st->regmap,
MAX31827_CONFIGURATION_REG,
MAX31827_CONFIGURATION_CNV_RATE_MASK,
- val);
+ res);
}
break;
@@ -376,14 +450,121 @@ static int max31827_write(struct device *dev, enum hwmon_sensor_types type,
return -EOPNOTSUPP;
}
-static int max31827_init_client(struct max31827_state *st)
+static ssize_t cfg_show(struct device *dev, struct device_attribute *devattr,
+ char *buf)
{
+ struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
+ struct max31827_state *st = dev_get_drvdata(dev);
+ const unsigned int mask = cfg_masks[attr->index];
+ unsigned int val, res;
+ int ret;
+
+ ret = regmap_read(st->regmap, MAX31827_CONFIGURATION_REG, &val);
+ /*
+ * FIELD_GET did not work because mask is not a compile time constant.
+ * There is no bitfield check now.
+ */
+ val = (val & mask) >> max31827__bf_shf(mask);
+
+ if (attr->index == cfg_res_idx)
+ res = max31827_resolutions[val];
+ else
+ res = !val;
+
+ return scnprintf(buf, PAGE_SIZE, "%u\n", res);
+}
+
+static ssize_t cfg_store(struct device *dev, struct device_attribute *devattr,
+ const char *buf, size_t count)
+{
+ struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
+ struct max31827_state *st = dev_get_drvdata(dev);
+ const unsigned int mask = cfg_masks[attr->index];
+ unsigned int res = 0;
+ unsigned int val;
+ int ret;
+
+ ret = kstrtouint(buf, 10, &val);
+ if (ret)
+ return ret;
+
+ if (attr->index == cfg_res_idx) {
+ /*
+ * Convert the desired conversion rate into register
+ * bits. res is already initialized with 1.
+ *
+ * This was inspired by lm73 driver.
+ */
+ while (res < ARRAY_SIZE(max31827_resolutions) &&
+ val > max31827_resolutions[res])
+ res++;
+
+ if (res == ARRAY_SIZE(max31827_resolutions) ||
+ val != max31827_resolutions[res])
+ return -EOPNOTSUPP;
+
+ st->resolution = res;
+ } else {
+ res = !val;
+ }
+
+ /*
+ * FIELD_PREP did not work because mask is not a compile time constant.
+ * There is no bitfield check now.
+ */
+ res = (res << max31827__bf_shf(mask)) & mask;
+ ret = regmap_update_bits(st->regmap, MAX31827_CONFIGURATION_REG,
+ cfg_masks[attr->index], res);
+
+ return (ret) ? ret : count;
+}
+
+static SENSOR_DEVICE_ATTR_RW(cfg_resolution, cfg, cfg_res_idx);
+static SENSOR_DEVICE_ATTR_RW(cfg_timeout, cfg, cfg_timeout_idx);
+
+static struct attribute *max31827_attrs[] = {
+ &sensor_dev_attr_cfg_resolution.dev_attr.attr,
+ &sensor_dev_attr_cfg_timeout.dev_attr.attr,
+ NULL
+};
+ATTRIBUTE_GROUPS(max31827);
+
+static int max31827_init_client(struct max31827_state *st,
+ struct fwnode_handle *fwnode)
+{
+ bool comp_int, alrm_pol;
+ u32 flt_q, lsb_idx;
+ unsigned int res = 0;
+ int ret;
+
st->enable = true;
+ res |= MAX31827_DEVICE_ENABLE(1);
+
+ st->resolution = MAX31827_RES_12_BIT;
+ res |= MAX31827_CONFIGURATION_RESOLUTION_MASK;
- return regmap_update_bits(st->regmap, MAX31827_CONFIGURATION_REG,
- MAX31827_CONFIGURATION_1SHOT_MASK |
- MAX31827_CONFIGURATION_CNV_RATE_MASK,
- MAX31827_DEVICE_ENABLE(1));
+ comp_int = fwnode_property_read_bool(fwnode, "adi,comp-int");
+ res |= FIELD_PREP(MAX31827_CONFIGURATION_COMP_INT_MASK, comp_int);
+
+ alrm_pol = fwnode_property_read_bool(fwnode, "adi,alrm-pol");
+ res |= FIELD_PREP(MAX31827_CONFIGURATION_ALRM_POL_MASK, alrm_pol);
+
+ ret = fwnode_property_read_u32(fwnode, "adi,flt-q", &flt_q);
+ if (ret)
+ return ret;
+
+ /*
+ * Convert the desired fault queue into register bits.
+ */
+ lsb_idx = max31827__bf_shf(flt_q);
+ if (lsb_idx > 3 || flt_q != BIT(lsb_idx)) {
+ pr_err("max31827: Invalid data in fault queue\n");
+ return -EOPNOTSUPP;
+ }
+
+ res |= FIELD_PREP(MAX31827_CONFIGURATION_FLT_Q_MASK, lsb_idx);
+
+ return regmap_write(st->regmap, MAX31827_CONFIGURATION_REG, res);
}
static const struct hwmon_channel_info *max31827_info[] = {
@@ -411,6 +592,7 @@ static int max31827_probe(struct i2c_client *client)
struct device *dev = &client->dev;
struct device *hwmon_dev;
struct max31827_state *st;
+ struct fwnode_handle *fwnode;
int err;
if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_WORD_DATA))
@@ -427,13 +609,15 @@ 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);
+ fwnode = dev_fwnode(dev);
+
+ err = max31827_init_client(st, fwnode);
if (err)
return err;
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