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+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.onsemi.com/PowerSolutions/product.do?id=ADM1027
+ * Analog Devices ADT7463
+ Prefix: 'adt7463'
+ Addresses scanned: I2C 0x2c, 0x2d, 0x2e
+ Datasheet: http://www.onsemi.com/PowerSolutions/product.do?id=ADT7463
+ * Analog Devices ADT7468
+ Prefix: 'adt7468'
+ Addresses scanned: I2C 0x2c, 0x2d, 0x2e
+ Datasheet: http://www.onsemi.com/PowerSolutions/product.do?id=ADT7468
+ * SMSC EMC6D100, SMSC EMC6D101
+ Prefix: 'emc6d100'
+ Addresses scanned: I2C 0x2c, 0x2d, 0x2e
+ Datasheet: http://www.smsc.com/media/Downloads_Public/discontinued/6d100.pdf
+ * SMSC EMC6D102
+ Prefix: 'emc6d102'
+ Addresses scanned: I2C 0x2c, 0x2d, 0x2e
+ Datasheet: http://www.smsc.com/main/catalog/emc6d102.html
+ * SMSC EMC6D103
+ Prefix: 'emc6d103'
+ Addresses scanned: I2C 0x2c, 0x2d, 0x2e
+ Datasheet: http://www.smsc.com/main/catalog/emc6d103.html
+ * SMSC EMC6D103S
+ Prefix: 'emc6d103s'
+ Addresses scanned: I2C 0x2c, 0x2d, 0x2e
+ Datasheet: http://www.smsc.com/main/catalog/emc6d103s.html
+ 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>
+This driver implements support for the National Semiconductor LM85 and
+compatible chips including the Analog Devices ADM1027, ADT7463, ADT7468 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, ADT7463 and ADT7468 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 ADT7468 has a high-frequency PWM mode, where all PWM outputs are
+driven by a 22.5 kHz clock. This is a global mode, not per-PWM output,
+which means that setting any PWM frequency above 11.3 kHz will switch
+all 3 PWM outputs to a 22.5 kHz frequency. Conversely, setting any PWM
+frequency below 11.3 kHz will switch all 3 PWM outputs to a frequency
+between 10 and 100 Hz, which can then be tuned separately.
+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. EMC6D102 and EMC6D103 feature additional ADC bits thus extending precision
+of voltage and temperature channels.
+SMSC EMC6D103S is similar to EMC6D103, but does not support pwm#_auto_pwm_minctl
+and temp#_auto_temp_off.
+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, ADT7463 and ADT7468 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 and ADT7468 also have 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 its 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_minctl - this flags selects for temp#_auto_temp_off temperature
+ the behaviour 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. These features
+are not currently supported by the lm85 driver.
+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. These features are not currently supported by the lm85
+In addition to the ADM1027 features, the ADT7463 and ADT7468 also have
+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.