On 5/5/23 10:25, Daniel Matyas wrote:
MAX31827 is a low-power temperature switch with I2C interface.
The device is a ±1°C accuracy from -40°C to +125°C
(12 bits) local temperature switch and sensor with I2C/SM-
Bus interface. The combination of small 6-bump wafer-lev-
el package (WLP) and high accuracy makes this temper-
ature sensor/switch ideal for a wide range of applications.
Signed-off-by: Daniel Matyas <daniel.matyas@xxxxxxxxxx>
---
v5 -> v6: Corrected the mistakes with mutex. Explained why I shift the
last 4 bits in the .rst file. (because the LSB is 0.0625 degrees Celsius).
Documentation/hwmon/index.rst | 1 +
Documentation/hwmon/max31827.rst | 90 +++++++
MAINTAINERS | 2 +
drivers/hwmon/Kconfig | 11 +
drivers/hwmon/Makefile | 2 +-
drivers/hwmon/max31827.c | 430 +++++++++++++++++++++++++++++++
6 files changed, 535 insertions(+), 1 deletion(-)
create mode 100644 Documentation/hwmon/max31827.rst
create mode 100644 drivers/hwmon/max31827.c
diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
index fa1208c62855..8cc0922f3b36 100644
--- a/Documentation/hwmon/index.rst
+++ b/Documentation/hwmon/index.rst
@@ -140,6 +140,7 @@ Hardware Monitoring Kernel Drivers
max31760
max31785
max31790
+ max31827
max34440
max6620
max6639
diff --git a/Documentation/hwmon/max31827.rst b/Documentation/hwmon/max31827.rst
new file mode 100644
index 000000000000..b0971d05b8a4
--- /dev/null
+++ b/Documentation/hwmon/max31827.rst
@@ -0,0 +1,90 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Kernel driver max31827
+======================
+
+Supported chips:
+
+ * Maxim MAX31827
+
+ Prefix: 'max31827'
+
+ Addresses scanned: I2C 0x40 - 0x5f
+
+ Datasheet: Publicly available at the Analog Devices website
+
+ * Maxim MAX31828
+
+ Prefix: 'max31828'
+
+ Addresses scanned: I2C 0x40 - 0x5f
+
+ Datasheet: Publicly available at the Analog Devices website
+
+ * Maxim MAX31829
+
+ Prefix: 'max31829'
+
+ Addresses scanned: I2C 0x40 - 0x5f
+
+ Datasheet: Publicly available at the Analog Devices website
+
+
+Authors:
+ - Daniel Matyas <daniel.matyas@xxxxxxxxxx>
+
+Description
+-----------
+
+The chips supported by this driver are quite similar. The only difference
+between them is found in the default power-on behaviour of the chips. While the
+MAX31827's fault queue is set to 1, the other two chip's fault queue is set to
+4. Besides this, the MAX31829's alarm active state is high, while the other two
+chip's alarms are active on low. It is important to note that the chips can be
+configured to operate in the same manner with 1 write operation to the
+configuration register. From here on, we will refer to all these chips as
+MAX31827.
+
+MAX31827 implements a temperature sensor with a 6 WLP packaging scheme. This
+sensor measures the temperature of the chip itself.
+
+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.
+
+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
+reset may be required before it begins to behave normally. To prevent this,
+it is recommended to perform a read of the configuration/status register to
+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.
+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 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
+lost. The step between 2 consecutive values is 62 or 63. This effect can be seen
+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.
+
+Notes
+-----
+
+Currently fault queue, alarm polarity and resolution cannot be modified.
+PEC is not implemented either.
diff --git a/MAINTAINERS b/MAINTAINERS
index 91de1e95f11d..40504fc94db5 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -12624,6 +12624,8 @@ L: linux-hwmon@xxxxxxxxxxxxxxx
S: Supported
W: http://ez.analog.com/community/linux-device-drivers
F: Documentation/devicetree/bindings/hwmon/adi,max31827.yaml
+F: Documentation/hwmon/max31827.rst
+F: drivers/hwmon/max31827.c
MAX6650 HARDWARE MONITOR AND FAN CONTROLLER DRIVER
L: linux-hwmon@xxxxxxxxxxxxxxx
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index fc640201a2de..12bd17075dc4 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -1097,6 +1097,17 @@ config SENSORS_MAX31760
This driver can also be built as a module. If so, the module
will be called max31760.
+config MAX31827
+ tristate "MAX31827 low-power temperature switch and similar devices"
+ depends on I2C
+ select REGMAP_I2C
+ help
+ If you say yes here you get support for MAX31827, MAX31828 and
+ MAX31829 low-power temperature switches and sensors connected with I2C.
+
+ This driver can also be built as a module. If so, the module
+ will be called max31827.
+
config SENSORS_MAX6620
tristate "Maxim MAX6620 fan controller"
depends on I2C
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index cd8c568c80a9..8a8021f9ca9e 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -149,6 +149,7 @@ obj-$(CONFIG_SENSORS_MAX6642) += max6642.o
obj-$(CONFIG_SENSORS_MAX6650) += max6650.o
obj-$(CONFIG_SENSORS_MAX6697) += max6697.o
obj-$(CONFIG_SENSORS_MAX31790) += max31790.o
+obj-$(CONFIG_MAX31827) += max31827.o
obj-$(CONFIG_SENSORS_MC13783_ADC)+= mc13783-adc.o
obj-$(CONFIG_SENSORS_MC34VR500) += mc34vr500.o
obj-$(CONFIG_SENSORS_MCP3021) += mcp3021.o
@@ -224,4 +225,3 @@ obj-$(CONFIG_SENSORS_PECI) += peci/
obj-$(CONFIG_PMBUS) += pmbus/
ccflags-$(CONFIG_HWMON_DEBUG_CHIP) := -DDEBUG
-
diff --git a/drivers/hwmon/max31827.c b/drivers/hwmon/max31827.c
new file mode 100644
index 000000000000..03f5524d6d9b
--- /dev/null
+++ b/drivers/hwmon/max31827.c
@@ -0,0 +1,430 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * max31827.c - Support for Maxim Low-Power Switch
+ *
+ * Copyright (c) 2023 Daniel Matyas <daniel.matyas@xxxxxxxxxx>
+ */
+
+#include <linux/bitfield.h>
+#include <linux/bitops.h>
+#include <linux/delay.h>
+#include <linux/hwmon.h>
+#include <linux/i2c.h>
+#include <linux/mutex.h>
+#include <linux/regmap.h>
+
+#define MAX31827_T_REG 0x0
+#define MAX31827_CONFIGURATION_REG 0x2
+#define MAX31827_TH_REG 0x4
+#define MAX31827_TL_REG 0x6
+#define MAX31827_TH_HYST_REG 0x8
+#define MAX31827_TL_HYST_REG 0xA
+
+#define MAX31827_CONFIGURATION_1SHOT_MASK BIT(0)
+#define MAX31827_CONFIGURATION_CNV_RATE_MASK GENMASK(3, 1)
+#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_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)
+
+struct max31827_state {
+ /*
+ * Prevent simultaneous access to the i2c client.
+ */
+ struct mutex lock;
+ struct regmap *regmap;
+ bool enable;
+};
+
+static const struct regmap_config max31827_regmap = {
+ .reg_bits = 8,
+ .val_bits = 16,
+ .max_register = 0xA,
+};
+
+static int write_alarm_val(struct max31827_state *st, unsigned int reg,
+ long val)
+{
+ unsigned int cfg;
+ unsigned int tmp;
+ int ret;
+
+ val = MAX31827_M_DGR_TO_16_BIT(val);
+
+ /*
+ * Before the Temperature Threshold Alarm and Alarm Hysteresis Threshold
+ * register values 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.
+ */
+ mutex_lock(&st->lock);
+
+ if (!st->enable) {
+ mutex_unlock(&st->lock);
+ return regmap_write(st->regmap, reg, val);
That defeats the purpose of the lock. It should be something like
ret = regmap_write(st->regmap, reg, val);
goto unlock;
with
unlock:
mutex_unlock(&st->lock);
return ret;
+ }
+
+ ret = regmap_read(st->regmap, MAX31827_CONFIGURATION_REG, &cfg);
+ if (ret) {
+ mutex_unlock(&st->lock);
+ return ret;
goto unlock;
See Documentation/process/coding-style.rst, 7) "Centralized exiting of functions".
Same below.
+ }
+
+ tmp = cfg & ~(MAX31827_CONFIGURATION_1SHOT_MASK |
+ MAX31827_CONFIGURATION_CNV_RATE_MASK);
+ ret = regmap_write(st->regmap, MAX31827_CONFIGURATION_REG, tmp);
+ if (ret) {
+ mutex_unlock(&st->lock);
+ return ret;
+ }
+
+ ret = regmap_write(st->regmap, reg, val);
+ if (ret) {
+ mutex_unlock(&st->lock);
+ return ret;
+ }
+
+ ret = regmap_write(st->regmap, MAX31827_CONFIGURATION_REG, cfg);
+
+ mutex_unlock(&st->lock);
+
+ return ret;
+}
+
+static umode_t max31827_is_visible(const void *state,
+ enum hwmon_sensor_types type, u32 attr,
+ int channel)
+{
+ if (type == hwmon_temp) {
+ switch (attr) {
+ case hwmon_temp_enable:
+ case hwmon_temp_max:
+ case hwmon_temp_min:
+ case hwmon_temp_max_hyst:
+ case hwmon_temp_min_hyst:
+ return 0644;
+ case hwmon_temp_input:
+ case hwmon_temp_min_alarm:
+ case hwmon_temp_max_alarm:
+ return 0444;
+ default:
+ return 0;
+ }
+ } else if (type == hwmon_chip) {
+ if (attr == hwmon_chip_update_interval)
+ return 0644;
+ }
+
+ return 0;
+}
+
+static int max31827_read(struct device *dev, enum hwmon_sensor_types type,
+ u32 attr, int channel, long *val)
+{
+ struct max31827_state *st = dev_get_drvdata(dev);
+ unsigned int uval;
+ int ret;
+
+ switch (type) {
+ case hwmon_temp:
+ switch (attr) {
+ case hwmon_temp_enable:
+ ret = regmap_read(st->regmap,
+ MAX31827_CONFIGURATION_REG, &uval);
+ uval = FIELD_GET(MAX31827_CONFIGURATION_1SHOT_MASK |
+ MAX31827_CONFIGURATION_CNV_RATE_MASK,
+ uval);
+ *val = !!uval;
+
+ break;
+ case hwmon_temp_input:
+ mutex_lock(&st->lock);
+
+ if (!st->enable) {
+ /*
+ * This operation requires mutex protection,
+ * because the chip configuration should not
+ * be changed during the conversion process.
+ */
+
+ ret = regmap_update_bits(st->regmap,
+ MAX31827_CONFIGURATION_REG,
+ MAX31827_CONFIGURATION_1SHOT_MASK,
+ 1);
+ if (ret) {
+ mutex_unlock(&st->lock);
+ return ret;
+ }
+
+ msleep(MAX31827_12_BIT_CNV_TIME);
+ }
+ ret = regmap_read(st->regmap, MAX31827_T_REG, &uval);
+
+ mutex_unlock(&st->lock);
+
+ *val = MAX31827_16_BIT_TO_M_DGR(uval);
+
+ break;
+ case hwmon_temp_max:
+ ret = regmap_read(st->regmap, MAX31827_TH_REG, &uval);
+ *val = MAX31827_16_BIT_TO_M_DGR(uval);
+ break;
+ case hwmon_temp_max_hyst:
+ ret = regmap_read(st->regmap, MAX31827_TH_HYST_REG,
+ &uval);
+ *val = MAX31827_16_BIT_TO_M_DGR(uval);
+ break;
+ case hwmon_temp_max_alarm:
+ ret = regmap_read(st->regmap,
+ MAX31827_CONFIGURATION_REG, &uval);
+ *val = FIELD_GET(MAX31827_CONFIGURATION_O_TEMP_STAT_MASK,
+ uval);
+ break;
+ case hwmon_temp_min:
+ ret = regmap_read(st->regmap, MAX31827_TL_REG, &uval);
+ *val = MAX31827_16_BIT_TO_M_DGR(uval);
+ break;
+ case hwmon_temp_min_hyst:
+ ret = regmap_read(st->regmap, MAX31827_TL_HYST_REG,
+ &uval);
+ *val = MAX31827_16_BIT_TO_M_DGR(uval);
+ break;
+ case hwmon_temp_min_alarm:
+ ret = regmap_read(st->regmap,
+ MAX31827_CONFIGURATION_REG, &uval);
+ *val = FIELD_GET(MAX31827_CONFIGURATION_U_TEMP_STAT_MASK,
+ uval);
+ break;
+ default:
+ ret = -EOPNOTSUPP;
+ break;
+ }
+
+ break;
+
+ case hwmon_chip:
+ if (attr == hwmon_chip_update_interval) {
+ ret = regmap_read(st->regmap,
+ MAX31827_CONFIGURATION_REG, &uval);
if (ret)
break;
because calculations don't really make sense in that case.
Same everywhere above where you do the same.
+ 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;
+ }
+ }
+ break;
+
+ default:
+ ret = -EOPNOTSUPP;
+ break;
+ }
+
+ return ret;
+}
+
+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);
+
+ switch (type) {
+ case hwmon_temp:
+ switch (attr) {
+ case hwmon_temp_enable:
+ if (val >> 1)
+ return -EOPNOTSUPP;
+
+ st->enable = val;
+
+ return regmap_update_bits(st->regmap,
+ MAX31827_CONFIGURATION_REG,
+ MAX31827_CONFIGURATION_1SHOT_MASK |
+ MAX31827_CONFIGURATION_CNV_RATE_MASK,
+ MAX31827_DEVICE_ENABLE(val));
The missing lock here makes the mutex above quite pointless. The chip can
still be enabled while the above code is waiting for a conversion result
from a disabled chip. Similar, the mutex in write_alarm_val is pointless
without a lock here because that means that the enable status can change
while the mutex is locked.
On top of that, changing st->enable and then the register without lock means
that it is not well defined if the flag and the actual chip status are
in sync.
+
+ case hwmon_temp_max:
+ return write_alarm_val(st, MAX31827_TH_REG, val);
+
+ case hwmon_temp_max_hyst:
+ return write_alarm_val(st, MAX31827_TH_HYST_REG, val);
+
+ case hwmon_temp_min:
+ return write_alarm_val(st, MAX31827_TL_REG, val);
+
+ case hwmon_temp_min_hyst:
+ return write_alarm_val(st, MAX31827_TL_HYST_REG, val);
+
+ default:
+ return -EOPNOTSUPP;
+ }
+
+ case hwmon_chip:
+ if (attr == hwmon_chip_update_interval) {
+ 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:
+ return -EOPNOTSUPP;
+ }
+
+ val = FIELD_PREP(MAX31827_CONFIGURATION_CNV_RATE_MASK,
+ val);
+
+ return regmap_update_bits(st->regmap,
+ MAX31827_CONFIGURATION_REG,
+ MAX31827_CONFIGURATION_CNV_RATE_MASK,
+ val);
Doesn't this automatically enable the chip ?
+ }
+ break;
+
+ default:
+ return -EOPNOTSUPP;
+ }
+
+ return -EOPNOTSUPP;
+}
+
+static int max31827_init_client(struct max31827_state *st)
+{
+ st->enable = true;
+
+ return regmap_update_bits(st->regmap, MAX31827_CONFIGURATION_REG,
+ MAX31827_CONFIGURATION_1SHOT_MASK |
+ MAX31827_CONFIGURATION_CNV_RATE_MASK,
+ MAX31827_DEVICE_ENABLE(1));
+}
+
+static const struct hwmon_channel_info *max31827_info[] = {
+ HWMON_CHANNEL_INFO(temp, HWMON_T_ENABLE | HWMON_T_INPUT | HWMON_T_MIN |
+ HWMON_T_MIN_HYST | HWMON_T_MIN_ALARM |
+ HWMON_T_MAX | HWMON_T_MAX_HYST |
+ HWMON_T_MAX_ALARM),
+ HWMON_CHANNEL_INFO(chip, HWMON_C_UPDATE_INTERVAL),
+ NULL,
+};
+
+static const struct hwmon_ops max31827_hwmon_ops = {
+ .is_visible = max31827_is_visible,
+ .read = max31827_read,
+ .write = max31827_write,
+};
+
+static const struct hwmon_chip_info max31827_chip_info = {
+ .ops = &max31827_hwmon_ops,
+ .info = max31827_info,
+};
+
+static int max31827_probe(struct i2c_client *client)
+{
+ struct device *dev = &client->dev;
+ struct device *hwmon_dev;
+ struct max31827_state *st;
+ int err;
+
+ if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_WORD_DATA))
+ return -EOPNOTSUPP;
+
+ st = devm_kzalloc(dev, sizeof(*st), GFP_KERNEL);
+ if (!st)
+ return -ENOMEM;
+
+ mutex_init(&st->lock);
+
+ st->regmap = devm_regmap_init_i2c(client, &max31827_regmap);
+ if (IS_ERR(st->regmap))
+ return dev_err_probe(dev, PTR_ERR(st->regmap),
+ "Failed to allocate regmap.\n");
+
+ err = max31827_init_client(st);
+ if (err)
+ return err;
+
+ hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name, st,
+ &max31827_chip_info,
+ NULL);
+
+ 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 = "max31827" },
+ { }
+};
+MODULE_DEVICE_TABLE(of, max31827_of_match);
+
+static struct i2c_driver max31827_driver = {
+ .class = I2C_CLASS_HWMON,
+ .driver = {
+ .name = "max31827",
+ .of_match_table = max31827_of_match,
+ },
+ .probe_new = max31827_probe,
+ .id_table = max31827_i2c_ids,
+};
+module_i2c_driver(max31827_driver);
+
+MODULE_AUTHOR("Daniel Matyas <daniel.matyas@xxxxxxxxxx>");
+MODULE_DESCRIPTION("Maxim MAX31827 low-power temperature switch driver");
+MODULE_LICENSE("GPL");
