From 88548710d2aed71677f7594a78219bf081d4297f Mon Sep 17 00:00:00 2001 From: Daniel Matyas Date: Tue, 31 Oct 2023 20:21:53 +0200 Subject: hwmon: (max31827) Handle new properties from the devicetree Used fwnode to retrieve data from the devicetree in the init_client function. If the uint32 properties are not present, the default values are used for max31827 chip. Signed-off-by: Daniel Matyas Link: https://lore.kernel.org/r/20231031182158.124608-1-daniel.matyas@analog.com Signed-off-by: Guenter Roeck --- Documentation/hwmon/max31827.rst | 48 ++++++++++++++++++++++++++++++++-------- 1 file changed, 39 insertions(+), 9 deletions(-) (limited to 'Documentation/hwmon') diff --git a/Documentation/hwmon/max31827.rst b/Documentation/hwmon/max31827.rst index 9a1055a007cf..a8bbfb85dd02 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 @@ -68,6 +76,18 @@ 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 @@ -83,8 +103,18 @@ 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 and resolution are not implemented. -- cgit v1.2.3