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Kernel driver lm85

==================

Supported chips:

  * National Semiconductor LM85 (B and C versions)

    Prefix: 'lm85'

    Addresses scanned: I2C 0x2c, 0x2d, 0x2e

    Datasheet: http://www.national.com/pf/LM/LM85.html

  * Analog Devices ADM1027

    Prefix: 'adm1027'

    Addresses scanned: I2C 0x2c, 0x2d, 0x2e

    Datasheet: http://www.analog.com/en/prod/0,,766_825_ADM1027,00.html

  * Analog Devices ADT7463

    Prefix: 'adt7463'

    Addresses scanned: I2C 0x2c, 0x2d, 0x2e

    Datasheet: http://www.analog.com/en/prod/0,,766_825_ADT7463,00.html

  * SMSC EMC6D100, SMSC EMC6D101

    Prefix: 'emc6d100'

    Addresses scanned: I2C 0x2c, 0x2d, 0x2e

    Datasheet: http://www.smsc.com/main/tools/discontinued/6d100.pdf

  * SMSC EMC6D102

    Prefix: 'emc6d102'

    Addresses scanned: I2C 0x2c, 0x2d, 0x2e

    Datasheet: http://www.smsc.com/main/catalog/emc6d102.html

Authors:

        Philip Pokorny ,

        Frodo Looijaard ,

        Richard Barrington ,

        Margit Schubert-While ,

        Justin Thiessen 

Description

-----------

This driver implements support for the National Semiconductor LM85 and

compatible chips including the Analog Devices ADM1027, ADT7463 and

SMSC EMC6D10x chips family.

The LM85 uses the 2-wire interface compatible with the SMBUS 2.0

specification. Using an analog to digital converter it measures three (3)

temperatures and five (5) voltages. It has four (4) 16-bit counters for

measuring fan speed. Five (5) digital inputs are provided for sampling the

VID signals from the processor to the VRM. Lastly, there are three (3) PWM

outputs that can be used to control fan speed.

The voltage inputs have internal scaling resistors so that the following

voltage can be measured without external resistors:

  2.5V, 3.3V, 5V, 12V, and CPU core voltage (2.25V)

The temperatures measured are one internal diode, and two remote diodes.

Remote 1 is generally the CPU temperature. These inputs are designed to

measure a thermal diode like the one in a Pentium 4 processor in a socket

423 or socket 478 package. They can also measure temperature using a

transistor like the 2N3904.

A sophisticated control system for the PWM outputs is designed into the

LM85 that allows fan speed to be adjusted automatically based on any of the

three temperature sensors. Each PWM output is individually adjustable and

programmable. Once configured, the LM85 will adjust the PWM outputs in

response to the measured temperatures without further host intervention.

This feature can also be disabled for manual control of the PWM's.

Each of the measured inputs (voltage, temperature, fan speed) has

corresponding high/low limit values. The LM85 will signal an ALARM if any

measured value exceeds either limit.

The LM85 samples all inputs continuously. The lm85 driver will not read

the registers more often than once a second. Further, configuration data is

only read once each 5 minutes. There is twice as much config data as

measurements, so this would seem to be a worthwhile optimization.

Special Features

----------------

The LM85 has four fan speed monitoring modes. The ADM1027 has only two.

Both have special circuitry to compensate for PWM interactions with the

TACH signal from the fans. The ADM1027 can be configured to measure the

speed of a two wire fan, but the input conditioning circuitry is different

for 3-wire and 2-wire mode. For this reason, the 2-wire fan modes are not

exposed to user control. The BIOS should initialize them to the correct

mode. If you've designed your own ADM1027, you'll have to modify the

init_client function and add an insmod parameter to set this up.

To smooth the response of fans to changes in temperature, the LM85 has an

optional filter for smoothing temperatures. The ADM1027 has the same

config option but uses it to rate limit the changes to fan speed instead.

The ADM1027 and ADT7463 have a 10-bit ADC and can therefore measure

temperatures with 0.25 degC resolution. They also provide an offset to the

temperature readings that is automatically applied during measurement.

This offset can be used to zero out any errors due to traces and placement.

The documentation says that the offset is in 0.25 degC steps, but in

initial testing of the ADM1027 it was 1.00 degC steps. Analog Devices has

confirmed this "bug". The ADT7463 is reported to work as described in the

documentation. The current lm85 driver does not show the offset register.

The ADT7463 has a THERM asserted counter. This counter has a 22.76ms

resolution and a range of 5.8 seconds. The driver implements a 32-bit

accumulator of the counter value to extend the range to over a year. The

counter will stay at it's max value until read.

See the vendor datasheets for more information. There is application note

from National (AN-1260) with some additional information about the LM85.

The Analog Devices datasheet is very detailed and describes a procedure for

determining an optimal configuration for the automatic PWM control.

The SMSC EMC6D100 & EMC6D101 monitor external voltages, temperatures, and

fan speeds. They use this monitoring capability to alert the system to out

of limit conditions and can automatically control the speeds of multiple

fans in a PC or embedded system. The EMC6D101, available in a 24-pin SSOP

package, and the EMC6D100, available in a 28-pin SSOP package, are designed

to be register compatible. The EMC6D100 offers all the features of the

EMC6D101 plus additional voltage monitoring and system control features.

Unfortunately it is not possible to distinguish between the package

versions on register level so these additional voltage inputs may read

zero. The EMC6D102 features addtional ADC bits thus extending precision

of voltage and temperature channels.

Hardware Configurations

-----------------------

The LM85 can be jumpered for 3 different SMBus addresses. There are

no other hardware configuration options for the LM85.

The lm85 driver detects both LM85B and LM85C revisions of the chip. See the

datasheet for a complete description of the differences. Other than

identifying the chip, the driver behaves no differently with regard to

these two chips. The LM85B is recommended for new designs.

The ADM1027 and ADT7463 chips have an optional SMBALERT output that can be

used to signal the chipset in case a limit is exceeded or the temperature

sensors fail. Individual sensor interrupts can be masked so they won't

trigger SMBALERT. The SMBALERT output if configured replaces one of the other

functions (PWM2 or IN0). This functionality is not implemented in current

driver.

The ADT7463 also has an optional THERM output/input which can be connected

to the processor PROC_HOT output. If available, the autofan control

dynamic Tmin feature can be enabled to keep the system temperature within

spec (just?!) with the least possible fan noise.

Configuration Notes

-------------------

Besides standard interfaces driver adds following:

* Temperatures and Zones

Each temperature sensor is associated with a Zone. There are three

sensors and therefore three zones (# 1, 2 and 3). Each zone has the following

temperature configuration points:

* temp#_auto_temp_off - temperature below which fans should be off or spinning very low.

* temp#_auto_temp_min - temperature over which fans start to spin.

* temp#_auto_temp_max - temperature when fans spin at full speed.

* temp#_auto_temp_crit - temperature when all fans will run full speed.

* PWM Control

There are three PWM outputs. The LM85 datasheet suggests that the

pwm3 output control both fan3 and fan4. Each PWM can be individually

configured and assigned to a zone for it's control value. Each PWM can be

configured individually according to the following options.

* pwm#_auto_pwm_min - this specifies the PWM value for temp#_auto_temp_off

                      temperature. (PWM value from 0 to 255)

* pwm#_auto_pwm_freq - select base frequency of PWM output. You can select

                       in range of 10.0 to 94.0 Hz in .1 Hz units.

                       (Values 100 to 940).

The pwm#_auto_pwm_freq can be set to one of the following 8 values. Setting the

frequency to a value not on this list, will result in the next higher frequency

being selected. The actual device frequency may vary slightly from this

specification as designed by the manufacturer. Consult the datasheet for more

details. (PWM Frequency values:  100, 150, 230, 300, 380, 470, 620, 940)

* pwm#_auto_pwm_minctl - this flags selects for temp#_auto_temp_off temperature

                         the bahaviour of fans. Write 1 to let fans spinning at

                         pwm#_auto_pwm_min or write 0 to let them off.

NOTE: It has been reported that there is a bug in the LM85 that causes the flag

to be associated with the zones not the PWMs. This contradicts all the

published documentation. Setting pwm#_min_ctl in this case actually affects all

PWMs controlled by zone '#'.

* PWM Controlling Zone selection

* pwm#_auto_channels - controls zone that is associated with PWM

Configuration choices:

   Value     Meaning

  ------  ------------------------------------------------

      1    Controlled by Zone 1

      2    Controlled by Zone 2

      3    Controlled by Zone 3

     23    Controlled by higher temp of Zone 2 or 3

    123    Controlled by highest temp of Zone 1, 2 or 3

     -1    PWM always 100%  (full on)

     -2    Manual control (write to 'pwm#' to set)

The National LM85's have two vendor specific configuration

features. Tach. mode and Spinup Control. For more details on these,

see the LM85 datasheet or Application Note AN-1260.

The Analog Devices ADM1027 has several vendor specific enhancements.

The number of pulses-per-rev of the fans can be set, Tach monitoring

can be optimized for PWM operation, and an offset can be applied to

the temperatures to compensate for systemic errors in the

measurements.

In addition to the ADM1027 features, the ADT7463 also has Tmin control

and THERM asserted counts. Automatic Tmin control acts to adjust the

Tmin value to maintain the measured temperature sensor at a specified

temperature. There isn't much documentation on this feature in the

ADT7463 data sheet. This is not supported by current driver.