diff mbox series

[v7,2/2] hwmon: max31827: add MAX31827 driver

Message ID 20230508172427.23915-2-daniel.matyas@analog.com
State Superseded
Headers show
Series None | expand

Commit Message

Matyas, Daniel May 8, 2023, 5:24 p.m. UTC
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@analog.com>
---

v6 -> v7 : Used goto instead of return in write_alarm_val function.
Unlocked mutex in goto label.

Used mutex for enable.

Now update_interval can only be modified if the device is enabled. I did
this, b.c. modifying the update interval, when the device is in shutdown
mode, automatically enables the device.

 Documentation/hwmon/index.rst    |   1 +
 Documentation/hwmon/max31827.rst |  90 ++++++
 MAINTAINERS                      |   2 +
 drivers/hwmon/Kconfig            |  11 +
 drivers/hwmon/Makefile           |   2 +-
 drivers/hwmon/max31827.c         | 466 +++++++++++++++++++++++++++++++
 6 files changed, 571 insertions(+), 1 deletion(-)
 create mode 100644 Documentation/hwmon/max31827.rst
 create mode 100644 drivers/hwmon/max31827.c

Comments

kernel test robot May 11, 2023, 3:21 p.m. UTC | #1
Hi Daniel,

kernel test robot noticed the following build warnings:

[auto build test WARNING on groeck-staging/hwmon-next]
[also build test WARNING on robh/for-next linus/master v6.4-rc1 next-20230511]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Daniel-Matyas/hwmon-max31827-add-MAX31827-driver/20230508-222643
base:   https://git.kernel.org/pub/scm/linux/kernel/git/groeck/linux-staging.git hwmon-next
patch link:    https://lore.kernel.org/r/20230508172427.23915-2-daniel.matyas%40analog.com
patch subject: [PATCH v7 2/2] hwmon: max31827: add MAX31827 driver
config: hexagon-allyesconfig (https://download.01.org/0day-ci/archive/20230511/202305112351.DBkFfs76-lkp@intel.com/config)
compiler: clang version 17.0.0 (https://github.com/llvm/llvm-project b0fb98227c90adf2536c9ad644a74d5e92961111)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/89289262b54eadd8ac5f955bd358ed6d9a51908a
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Daniel-Matyas/hwmon-max31827-add-MAX31827-driver/20230508-222643
        git checkout 89289262b54eadd8ac5f955bd358ed6d9a51908a
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=hexagon olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=hexagon SHELL=/bin/bash drivers/hwmon/

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Link: https://lore.kernel.org/oe-kbuild-all/202305112351.DBkFfs76-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from drivers/hwmon/max31827.c:12:
   In file included from include/linux/i2c.h:19:
   In file included from include/linux/regulator/consumer.h:35:
   In file included from include/linux/suspend.h:5:
   In file included from include/linux/swap.h:9:
   In file included from include/linux/memcontrol.h:13:
   In file included from include/linux/cgroup.h:26:
   In file included from include/linux/kernel_stat.h:9:
   In file included from include/linux/interrupt.h:11:
   In file included from include/linux/hardirq.h:11:
   In file included from ./arch/hexagon/include/generated/asm/hardirq.h:1:
   In file included from include/asm-generic/hardirq.h:17:
   In file included from include/linux/irq.h:20:
   In file included from include/linux/io.h:13:
   In file included from arch/hexagon/include/asm/io.h:334:
   include/asm-generic/io.h:547:31: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           val = __raw_readb(PCI_IOBASE + addr);
                             ~~~~~~~~~~ ^
   include/asm-generic/io.h:560:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           val = __le16_to_cpu((__le16 __force)__raw_readw(PCI_IOBASE + addr));
                                                           ~~~~~~~~~~ ^
   include/uapi/linux/byteorder/little_endian.h:37:51: note: expanded from macro '__le16_to_cpu'
   #define __le16_to_cpu(x) ((__force __u16)(__le16)(x))
                                                     ^
   In file included from drivers/hwmon/max31827.c:12:
   In file included from include/linux/i2c.h:19:
   In file included from include/linux/regulator/consumer.h:35:
   In file included from include/linux/suspend.h:5:
   In file included from include/linux/swap.h:9:
   In file included from include/linux/memcontrol.h:13:
   In file included from include/linux/cgroup.h:26:
   In file included from include/linux/kernel_stat.h:9:
   In file included from include/linux/interrupt.h:11:
   In file included from include/linux/hardirq.h:11:
   In file included from ./arch/hexagon/include/generated/asm/hardirq.h:1:
   In file included from include/asm-generic/hardirq.h:17:
   In file included from include/linux/irq.h:20:
   In file included from include/linux/io.h:13:
   In file included from arch/hexagon/include/asm/io.h:334:
   include/asm-generic/io.h:573:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           val = __le32_to_cpu((__le32 __force)__raw_readl(PCI_IOBASE + addr));
                                                           ~~~~~~~~~~ ^
   include/uapi/linux/byteorder/little_endian.h:35:51: note: expanded from macro '__le32_to_cpu'
   #define __le32_to_cpu(x) ((__force __u32)(__le32)(x))
                                                     ^
   In file included from drivers/hwmon/max31827.c:12:
   In file included from include/linux/i2c.h:19:
   In file included from include/linux/regulator/consumer.h:35:
   In file included from include/linux/suspend.h:5:
   In file included from include/linux/swap.h:9:
   In file included from include/linux/memcontrol.h:13:
   In file included from include/linux/cgroup.h:26:
   In file included from include/linux/kernel_stat.h:9:
   In file included from include/linux/interrupt.h:11:
   In file included from include/linux/hardirq.h:11:
   In file included from ./arch/hexagon/include/generated/asm/hardirq.h:1:
   In file included from include/asm-generic/hardirq.h:17:
   In file included from include/linux/irq.h:20:
   In file included from include/linux/io.h:13:
   In file included from arch/hexagon/include/asm/io.h:334:
   include/asm-generic/io.h:584:33: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           __raw_writeb(value, PCI_IOBASE + addr);
                               ~~~~~~~~~~ ^
   include/asm-generic/io.h:594:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           __raw_writew((u16 __force)cpu_to_le16(value), PCI_IOBASE + addr);
                                                         ~~~~~~~~~~ ^
   include/asm-generic/io.h:604:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           __raw_writel((u32 __force)cpu_to_le32(value), PCI_IOBASE + addr);
                                                         ~~~~~~~~~~ ^
>> drivers/hwmon/max31827.c:238:7: warning: variable 'ret' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
                   if (attr == hwmon_chip_update_interval) {
                       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   drivers/hwmon/max31827.c:280:9: note: uninitialized use occurs here
           return ret;
                  ^~~
   drivers/hwmon/max31827.c:238:3: note: remove the 'if' if its condition is always true
                   if (attr == hwmon_chip_update_interval) {
                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   drivers/hwmon/max31827.c:134:9: note: initialize the variable 'ret' to silence this warning
           int ret;
                  ^
                   = 0
   7 warnings generated.


vim +238 drivers/hwmon/max31827.c

   128	
   129	static int max31827_read(struct device *dev, enum hwmon_sensor_types type,
   130				 u32 attr, int channel, long *val)
   131	{
   132		struct max31827_state *st = dev_get_drvdata(dev);
   133		unsigned int uval;
   134		int ret;
   135	
   136		switch (type) {
   137		case hwmon_temp:
   138			switch (attr) {
   139			case hwmon_temp_enable:
   140				ret = regmap_read(st->regmap,
   141						  MAX31827_CONFIGURATION_REG, &uval);
   142				if (ret)
   143					break;
   144	
   145				uval = FIELD_GET(MAX31827_CONFIGURATION_1SHOT_MASK |
   146						 MAX31827_CONFIGURATION_CNV_RATE_MASK,
   147						 uval);
   148				*val = !!uval;
   149	
   150				break;
   151			case hwmon_temp_input:
   152				mutex_lock(&st->lock);
   153	
   154				if (!st->enable) {
   155					/*
   156					 * This operation requires mutex protection,
   157					 * because the chip configuration should not
   158					 * be changed during the conversion process.
   159					 */
   160	
   161					ret = regmap_update_bits(st->regmap,
   162								 MAX31827_CONFIGURATION_REG,
   163								 MAX31827_CONFIGURATION_1SHOT_MASK,
   164								 1);
   165					if (ret) {
   166						mutex_unlock(&st->lock);
   167						return ret;
   168					}
   169	
   170					msleep(MAX31827_12_BIT_CNV_TIME);
   171				}
   172				ret = regmap_read(st->regmap, MAX31827_T_REG, &uval);
   173	
   174				mutex_unlock(&st->lock);
   175	
   176				if (ret)
   177					break;
   178	
   179				*val = MAX31827_16_BIT_TO_M_DGR(uval);
   180	
   181				break;
   182			case hwmon_temp_max:
   183				ret = regmap_read(st->regmap, MAX31827_TH_REG, &uval);
   184				if (ret)
   185					break;
   186	
   187				*val = MAX31827_16_BIT_TO_M_DGR(uval);
   188				break;
   189			case hwmon_temp_max_hyst:
   190				ret = regmap_read(st->regmap, MAX31827_TH_HYST_REG,
   191						  &uval);
   192				if (ret)
   193					break;
   194	
   195				*val = MAX31827_16_BIT_TO_M_DGR(uval);
   196				break;
   197			case hwmon_temp_max_alarm:
   198				ret = regmap_read(st->regmap,
   199						  MAX31827_CONFIGURATION_REG, &uval);
   200				if (ret)
   201					break;
   202	
   203				*val = FIELD_GET(MAX31827_CONFIGURATION_O_TEMP_STAT_MASK,
   204						 uval);
   205				break;
   206			case hwmon_temp_min:
   207				ret = regmap_read(st->regmap, MAX31827_TL_REG, &uval);
   208				if (ret)
   209					break;
   210	
   211				*val = MAX31827_16_BIT_TO_M_DGR(uval);
   212				break;
   213			case hwmon_temp_min_hyst:
   214				ret = regmap_read(st->regmap, MAX31827_TL_HYST_REG,
   215						  &uval);
   216				if (ret)
   217					break;
   218	
   219				*val = MAX31827_16_BIT_TO_M_DGR(uval);
   220				break;
   221			case hwmon_temp_min_alarm:
   222				ret = regmap_read(st->regmap,
   223						  MAX31827_CONFIGURATION_REG, &uval);
   224				if (ret)
   225					break;
   226	
   227				*val = FIELD_GET(MAX31827_CONFIGURATION_U_TEMP_STAT_MASK,
   228						 uval);
   229				break;
   230			default:
   231				ret = -EOPNOTSUPP;
   232				break;
   233			}
   234	
   235			break;
   236	
   237		case hwmon_chip:
 > 238			if (attr == hwmon_chip_update_interval) {
   239				ret = regmap_read(st->regmap,
   240						  MAX31827_CONFIGURATION_REG, &uval);
   241				if (ret)
   242					break;
   243	
   244				uval = FIELD_GET(MAX31827_CONFIGURATION_CNV_RATE_MASK,
   245						 uval);
   246				switch (uval) {
   247				case MAX31827_CNV_1_DIV_64_HZ:
   248					*val = 64000;
   249					break;
   250				case MAX31827_CNV_1_DIV_32_HZ:
   251					*val = 32000;
   252					break;
   253				case MAX31827_CNV_1_DIV_16_HZ:
   254					*val = 16000;
   255					break;
   256				case MAX31827_CNV_1_DIV_4_HZ:
   257					*val = 4000;
   258					break;
   259				case MAX31827_CNV_1_HZ:
   260					*val = 1000;
   261					break;
   262				case MAX31827_CNV_4_HZ:
   263					*val = 250;
   264					break;
   265				case MAX31827_CNV_8_HZ:
   266					*val = 125;
   267					break;
   268				default:
   269					*val = 0;
   270					break;
   271				}
   272			}
   273			break;
   274	
   275		default:
   276			ret = -EOPNOTSUPP;
   277			break;
   278		}
   279	
   280		return ret;
   281	}
   282
diff mbox series

Patch

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@analog.com>
+
+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@vger.kernel.org
 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@vger.kernel.org
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..fce20f52a680
--- /dev/null
+++ b/drivers/hwmon/max31827.c
@@ -0,0 +1,466 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * max31827.c - Support for Maxim Low-Power Switch
+ *
+ * Copyright (c) 2023 Daniel Matyas <daniel.matyas@analog.com>
+ */
+
+#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) {
+		ret = regmap_write(st->regmap, reg, val);
+		goto unlock;
+	}
+
+	ret = regmap_read(st->regmap, MAX31827_CONFIGURATION_REG, &cfg);
+	if (ret)
+		goto unlock;
+
+	tmp = cfg & ~(MAX31827_CONFIGURATION_1SHOT_MASK |
+		      MAX31827_CONFIGURATION_CNV_RATE_MASK);
+	ret = regmap_write(st->regmap, MAX31827_CONFIGURATION_REG, tmp);
+	if (ret)
+		goto unlock;
+
+	ret = regmap_write(st->regmap, reg, val);
+	if (ret)
+		goto unlock;
+
+	ret = regmap_write(st->regmap, MAX31827_CONFIGURATION_REG, cfg);
+
+unlock:
+	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);
+			if (ret)
+				break;
+
+			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);
+
+			if (ret)
+				break;
+
+			*val = MAX31827_16_BIT_TO_M_DGR(uval);
+
+			break;
+		case hwmon_temp_max:
+			ret = regmap_read(st->regmap, MAX31827_TH_REG, &uval);
+			if (ret)
+				break;
+
+			*val = MAX31827_16_BIT_TO_M_DGR(uval);
+			break;
+		case hwmon_temp_max_hyst:
+			ret = regmap_read(st->regmap, MAX31827_TH_HYST_REG,
+					  &uval);
+			if (ret)
+				break;
+
+			*val = MAX31827_16_BIT_TO_M_DGR(uval);
+			break;
+		case hwmon_temp_max_alarm:
+			ret = regmap_read(st->regmap,
+					  MAX31827_CONFIGURATION_REG, &uval);
+			if (ret)
+				break;
+
+			*val = FIELD_GET(MAX31827_CONFIGURATION_O_TEMP_STAT_MASK,
+					 uval);
+			break;
+		case hwmon_temp_min:
+			ret = regmap_read(st->regmap, MAX31827_TL_REG, &uval);
+			if (ret)
+				break;
+
+			*val = MAX31827_16_BIT_TO_M_DGR(uval);
+			break;
+		case hwmon_temp_min_hyst:
+			ret = regmap_read(st->regmap, MAX31827_TL_HYST_REG,
+					  &uval);
+			if (ret)
+				break;
+
+			*val = MAX31827_16_BIT_TO_M_DGR(uval);
+			break;
+		case hwmon_temp_min_alarm:
+			ret = regmap_read(st->regmap,
+					  MAX31827_CONFIGURATION_REG, &uval);
+			if (ret)
+				break;
+
+			*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;
+
+			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);
+	int ret;
+
+	switch (type) {
+	case hwmon_temp:
+		switch (attr) {
+		case hwmon_temp_enable:
+			if (val >> 1)
+				return -EOPNOTSUPP;
+
+			mutex_lock(&st->lock);
+			/**
+			 * The chip should not be enabled while a conversion is
+			 * performed. Neither should the chip be enabled when
+			 * the alarm values are changed.
+			 */
+
+			st->enable = val;
+
+			ret = regmap_update_bits(st->regmap,
+						 MAX31827_CONFIGURATION_REG,
+						 MAX31827_CONFIGURATION_1SHOT_MASK |
+						 MAX31827_CONFIGURATION_CNV_RATE_MASK,
+						 MAX31827_DEVICE_ENABLE(val));
+
+			mutex_unlock(&st->lock);
+
+			return ret;
+
+		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) {
+			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:
+				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);
+		}
+		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@analog.com>");
+MODULE_DESCRIPTION("Maxim MAX31827 low-power temperature switch driver");
+MODULE_LICENSE("GPL");