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diff --git a/Documentation/hwmon/adm9240.rst b/Documentation/hwmon/adm9240.rst new file mode 100644 index 000000000000..91063b0f4c6f --- /dev/null +++ b/Documentation/hwmon/adm9240.rst @@ -0,0 +1,201 @@ +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 <jdelvare@suse.de> + +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. |
