xref: /openbmc/linux/Documentation/hwmon/smsc47m192.rst (revision c39f2d9db0fd81ea20bb5cce9b3f082ca63753e2)

Kernel driver smsc47m192
========================

Supported chips:

  * SMSC LPC47M192, LPC47M15x, LPC47M292 and LPC47M997

    Prefix: 'smsc47m192'

    Addresses scanned: I2C 0x2c - 0x2d

    Datasheet: The datasheet for LPC47M192 is publicly available from

	       http://www.smsc.com/

	       The LPC47M15x, LPC47M292 and LPC47M997 are compatible for

	       hardware monitoring.



Author:
      - Hartmut Rick <linux@rick.claranet.de>

      - Special thanks to Jean Delvare for careful checking
	of the code and many helpful comments and suggestions.


Description
-----------

This driver implements support for the hardware sensor capabilities
of the SMSC LPC47M192 and compatible Super-I/O chips.

These chips support 3 temperature channels and 8 voltage inputs
as well as CPU voltage VID input.

They do also have fan monitoring and control capabilities, but the
these features are accessed via ISA bus and are not supported by this
driver. Use the 'smsc47m1' driver for fan monitoring and control.

Voltages and temperatures are measured by an 8-bit ADC, the resolution
of the temperatures is 1 bit per degree C.
Voltages are scaled such that the nominal voltage corresponds to
192 counts, i.e. 3/4 of the full range. Thus the available range for
each voltage channel is 0V ... 255/192*(nominal voltage), the resolution
is 1 bit per (nominal voltage)/192.
Both voltage and temperature values are scaled by 1000, the sys files
show voltages in mV and temperatures in units of 0.001 degC.

The +12V analog voltage input channel (in4_input) is multiplexed with
bit 4 of the encoded CPU voltage. This means that you either get
a +12V voltage measurement or a 5 bit CPU VID, but not both.
The default setting is to use the pin as 12V input, and use only 4 bit VID.
This driver assumes that the information in the configuration register
is correct, i.e. that the BIOS has updated the configuration if
the motherboard has this input wired to VID4.

The temperature and voltage readings are updated once every 1.5 seconds.
Reading them more often repeats the same values.


sysfs interface
---------------

===================== ==========================================================
in0_input	      +2.5V voltage input
in1_input	      CPU voltage input (nominal 2.25V)
in2_input	      +3.3V voltage input
in3_input	      +5V voltage input
in4_input	      +12V voltage input (may be missing if used as VID4)
in5_input	      Vcc voltage input (nominal 3.3V)
		      This is the supply voltage of the sensor chip itself.
in6_input	      +1.5V voltage input
in7_input	      +1.8V voltage input

in[0-7]_min,
in[0-7]_max	      lower and upper alarm thresholds for in[0-7]_input reading

		      All voltages are read and written in mV.

in[0-7]_alarm	      alarm flags for voltage inputs
		      These files read '1' in case of alarm, '0' otherwise.

temp1_input	      chip temperature measured by on-chip diode
temp[2-3]_input	      temperature measured by external diodes (one of these
		      would typically be wired to the diode inside the CPU)

temp[1-3]_min,
temp[1-3]_max	      lower and upper alarm thresholds for temperatures

temp[1-3]_offset      temperature offset registers
		      The chip adds the offsets stored in these registers to
		      the corresponding temperature readings.
		      Note that temp1 and temp2 offsets share the same register,
		      they cannot both be different from zero at the same time.
		      Writing a non-zero number to one of them will reset the other
		      offset to zero.

		      All temperatures and offsets are read and written in
		      units of 0.001 degC.

temp[1-3]_alarm       alarm flags for temperature inputs, '1' in case of alarm,
		      '0' otherwise.
temp[2-3]_input_fault diode fault flags for temperature inputs 2 and 3.
		      A fault is detected if the two pins for the corresponding
		      sensor are open or shorted, or any of the two is shorted
		      to ground or Vcc. '1' indicates a diode fault.

cpu0_vid	      CPU voltage as received from the CPU

vrm		      CPU VID standard used for decoding CPU voltage
===================== ==========================================================

The `*_min`, `*_max`, `*_offset` and `vrm` files can be read and written,
all others are read-only.