From 16d60ba8fdc4c6e4745005889dea6ed82b6b5cbd Mon Sep 17 00:00:00 2001 From: Daniel Matyas Date: Wed, 24 May 2023 19:01:30 +0300 Subject: hwmon: Add MAX31827 driver MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Link: https://lore.kernel.org/r/20230524160131.14081-2-daniel.matyas@analog.com [groeck: Improved define alignment, return -EINVAL after bad user input, fixed up compatible statement] Signed-off-by: Guenter Roeck --- Documentation/hwmon/index.rst | 1 + Documentation/hwmon/max31827.rst | 90 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 91 insertions(+) create mode 100644 Documentation/hwmon/max31827.rst (limited to 'Documentation/hwmon') diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst index 03b30a94a9e6..b3af03214b3e 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 + +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. -- cgit v1.2.3