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Commit 57d60b1b authored by Guenter Roeck's avatar Guenter Roeck
Browse files

hwmon: (emc1403) Add driver documentation 



With the driver now supporting several chip variants,
it is about time to document what is supported.

Signed-off-by: default avatarGuenter Roeck <linux@roeck-us.net>
parent a9622663

Documentation/hwmon/emc1403

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Kernel driver emc1403

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



Supported chips:

  * SMSC / Microchip EMC1402, EMC1412

    Addresses scanned: I2C 0x18, 0x1c, 0x29, 0x4c, 0x4d, 0x5c

    Prefix: 'emc1402'

    Datasheets:

	http://ww1.microchip.com/downloads/en/DeviceDoc/1412.pdf

	http://ww1.microchip.com/downloads/en/DeviceDoc/1402.pdf

  * SMSC / Microchip EMC1403, EMC1404, EMC1413, EMC1414

    Addresses scanned: I2C 0x18, 0x29, 0x4c, 0x4d

    Prefix: 'emc1403', 'emc1404'

    Datasheets:

	http://ww1.microchip.com/downloads/en/DeviceDoc/1403_1404.pdf

	http://ww1.microchip.com/downloads/en/DeviceDoc/1413_1414.pdf

  * SMSC / Microchip EMC1422

    Addresses scanned: I2C 0x4c

    Prefix: 'emc1422'

    Datasheet:

	http://ww1.microchip.com/downloads/en/DeviceDoc/1422.pdf

  * SMSC / Microchip EMC1423, EMC1424

    Addresses scanned: I2C 0x4c

    Prefix: 'emc1423', 'emc1424'

    Datasheet:

	http://ww1.microchip.com/downloads/en/DeviceDoc/1423_1424.pdf



Author:

    Kalhan Trisal <kalhan.trisal@intel.com





Description

-----------



The Standard Microsystems Corporation (SMSC) / Microchip EMC14xx chips

contain up to four temperature sensors. EMC14x2 support two sensors

(one internal, one external). EMC14x3 support three sensors (one internal,

two external), and EMC14x4 support four sensors (one internal, three

external).



The chips implement three limits for each sensor: low (tempX_min), high

(tempX_max) and critical (tempX_crit.) The chips also implement an

hysteresis mechanism which applies to all limits. The relative difference

is stored in a single register on the chip, which means that the relative

difference between the limit and its hysteresis is always the same for

all three limits.



This implementation detail implies the following:

* When setting a limit, its hysteresis will automatically follow, the

  difference staying unchanged. For example, if the old critical limit

  was 80 degrees C, and the hysteresis was 75 degrees C, and you change

  the critical limit to 90 degrees C, then the hysteresis will

  automatically change to 85 degrees C.

* While hysteresis limits can be set for all critical limits, setting a single

  hysteresis value affects the hysteresis values for all limits on all sensors.

* The limits should be set before the hysteresis.