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-Kernel driver adm9240
-=====================
-
-Supported chips:
- * Analog Devices ADM9240
- Prefix: 'adm9240'
- Addresses scanned: I2C 0x2c - 0x2f
- Datasheet: Publicly available at the Analog Devices website
- http://www.analog.com/UploadedFiles/Data_Sheets/79857778ADM9240_0.pdf
-
- * Dallas Semiconductor DS1780
- Prefix: 'ds1780'
- Addresses scanned: I2C 0x2c - 0x2f
- Datasheet: Publicly available at the Dallas Semiconductor (Maxim) website
- http://pdfserv.maxim-ic.com/en/ds/DS1780.pdf
-
- * National Semiconductor LM81
- Prefix: 'lm81'
- Addresses scanned: I2C 0x2c - 0x2f
- Datasheet: Publicly available at the National Semiconductor website
- http://www.national.com/ds.cgi/LM/LM81.pdf
-
-Authors:
- Frodo Looijaard <frodol@dds.nl>,
- Philip Edelbrock <phil@netroedge.com>,
- Michiel Rook <michiel@grendelproject.nl>,
- Grant Coady <gcoady.lk@gmail.com> with guidance
- from Jean Delvare <khali@linux-fr.org>
-
-Interface
----------
-The I2C addresses listed above assume BIOS has not changed the
-chip MSB 5-bit address. Each chip reports a unique manufacturer
-identification code as well as the chip revision/stepping level.
-
-Description
------------
-[From ADM9240] The ADM9240 is a complete system hardware monitor for
-microprocessor-based systems, providing measurement and limit comparison
-of up to four power supplies and two processor core voltages, plus
-temperature, two fan speeds and chassis intrusion. Measured values can
-be read out via an I2C-compatible serial System Management Bus, and values
-for limit comparisons can be programmed in over the same serial bus. The
-high speed successive approximation ADC allows frequent sampling of all
-analog channels to ensure a fast interrupt response to any out-of-limit
-measurement.
-
-The ADM9240, DS1780 and LM81 are register compatible, the following
-details are common to the three chips. Chip differences are described
-after this section.
-
-
-Measurements
-------------
-The measurement cycle
-
-The adm9240 driver will take a measurement reading no faster than once
-each two seconds. User-space may read sysfs interface faster than the
-measurement update rate and will receive cached data from the most
-recent measurement.
-
-ADM9240 has a very fast 320us temperature and voltage measurement cycle
-with independent fan speed measurement cycles counting alternating rising
-edges of the fan tacho inputs.
-
-DS1780 measurement cycle is about once per second including fan speed.
-
-LM81 measurement cycle is about once per 400ms including fan speed.
-The LM81 12-bit extended temperature measurement mode is not supported.
-
-Temperature
------------
-On chip temperature is reported as degrees Celsius as 9-bit signed data
-with resolution of 0.5 degrees Celsius. High and low temperature limits
-are 8-bit signed data with resolution of one degree Celsius.
-
-Temperature alarm is asserted once the temperature exceeds the high limit,
-and is cleared when the temperature falls below the temp1_max_hyst value.
-
-Fan Speed
----------
-Two fan tacho inputs are provided, the ADM9240 gates an internal 22.5kHz
-clock via a divider to an 8-bit counter. Fan speed (rpm) is calculated by:
-
-rpm = (22500 * 60) / (count * divider)
-
-Automatic fan clock divider
-
- * User sets 0 to fan_min limit
- - low speed alarm is disabled
- - fan clock divider not changed
- - auto fan clock adjuster enabled for valid fan speed reading
-
- * User sets fan_min limit too low
- - low speed alarm is enabled
- - fan clock divider set to max
- - fan_min set to register value 254 which corresponds
- to 664 rpm on adm9240
- - low speed alarm will be asserted if fan speed is
- less than minimum measurable speed
- - auto fan clock adjuster disabled
-
- * User sets reasonable fan speed
- - low speed alarm is enabled
- - fan clock divider set to suit fan_min
- - auto fan clock adjuster enabled: adjusts fan_min
-
- * User sets unreasonably high low fan speed limit
- - resolution of the low speed limit may be reduced
- - alarm will be asserted
- - auto fan clock adjuster enabled: adjusts fan_min
-
- * fan speed may be displayed as zero until the auto fan clock divider
- adjuster brings fan speed clock divider back into chip measurement
- range, this will occur within a few measurement cycles.
-
-Analog Output
--------------
-An analog output provides a 0 to 1.25 volt signal intended for an external
-fan speed amplifier circuit. The analog output is set to maximum value on
-power up or reset. This doesn't do much on the test Intel SE440BX-2.
-
-Voltage Monitor
-
-Voltage (IN) measurement is internally scaled:
-
- nr label nominal maximum resolution
- mV mV mV
- 0 +2.5V 2500 3320 13.0
- 1 Vccp1 2700 3600 14.1
- 2 +3.3V 3300 4380 17.2
- 3 +5V 5000 6640 26.0
- 4 +12V 12000 15940 62.5
- 5 Vccp2 2700 3600 14.1
-
-The reading is an unsigned 8-bit value, nominal voltage measurement is
-represented by a reading of 192, being 3/4 of the measurement range.
-
-An alarm is asserted for any voltage going below or above the set limits.
-
-The driver reports and accepts voltage limits scaled to the above table.
-
-VID Monitor
------------
-The chip has five inputs to read the 5-bit VID and reports the mV value
-based on detected CPU type.
-
-Chassis Intrusion
------------------
-An alarm is asserted when the CI pin goes active high. The ADM9240
-Datasheet has an example of an external temperature sensor driving
-this pin. On an Intel SE440BX-2 the Chassis Intrusion header is
-connected to a normally open switch.
-
-The ADM9240 provides an internal open drain on this line, and may output
-a 20 ms active low pulse to reset an external Chassis Intrusion latch.
-
-Clear the CI latch by writing value 0 to the sysfs intrusion0_alarm file.
-
-Alarm flags reported as 16-bit word
-
- bit label comment
- --- ------------- --------------------------
- 0 +2.5 V_Error high or low limit exceeded
- 1 VCCP_Error high or low limit exceeded
- 2 +3.3 V_Error high or low limit exceeded
- 3 +5 V_Error high or low limit exceeded
- 4 Temp_Error temperature error
- 6 FAN1_Error fan low limit exceeded
- 7 FAN2_Error fan low limit exceeded
- 8 +12 V_Error high or low limit exceeded
- 9 VCCP2_Error high or low limit exceeded
- 12 Chassis_Error CI pin went high
-
-Remaining bits are reserved and thus undefined. It is important to note
-that alarm bits may be cleared on read, user-space may latch alarms and
-provide the end-user with a method to clear alarm memory.