| 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 1 to the sysfs chassis_clear 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. |
