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diff --git a/Documentation/i2c/chips/lm85 b/Documentation/i2c/chips/lm85 new file mode 100644 index 000000000000..9549237530cf --- /dev/null +++ b/Documentation/i2c/chips/lm85 @@ -0,0 +1,221 @@ +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 <ppokorny@penguincomputing.com>, + Frodo Looijaard <frodol@dds.nl>, + Richard Barrington <rich_b_nz@clear.net.nz>, + Margit Schubert-While <margitsw@t-online.de>, + Justin Thiessen <jthiessen@penguincomputing.com> + +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 + 0 PWM always 0% (off) + -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. |
