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+Kernel driver lm93
+==================
+
+Supported chips:
+
+  * National Semiconductor LM93
+
+    Prefix 'lm93'
+
+    Addresses scanned: I2C 0x2c-0x2e
+
+    Datasheet: http://www.national.com/ds.cgi/LM/LM93.pdf
+
+  * National Semiconductor LM94
+
+    Prefix 'lm94'
+
+    Addresses scanned: I2C 0x2c-0x2e
+
+    Datasheet: http://www.national.com/ds.cgi/LM/LM94.pdf
+
+
+Authors:
+        - Mark M. Hoffman <mhoffman@lightlink.com>
+        - Ported to 2.6 by Eric J. Bowersox <ericb@aspsys.com>
+        - Adapted to 2.6.20 by Carsten Emde <ce@osadl.org>
+        - Modified for mainline integration by Hans J. Koch <hjk@hansjkoch.de>
+
+Module Parameters
+-----------------
+
+* init: integer
+  Set to non-zero to force some initializations (default is 0).
+* disable_block: integer
+  A "0" allows SMBus block data transactions if the host supports them.  A "1"
+  disables SMBus block data transactions.  The default is 0.
+* vccp_limit_type: integer array (2)
+  Configures in7 and in8 limit type, where 0 means absolute and non-zero
+  means relative.  "Relative" here refers to "Dynamic Vccp Monitoring using
+  VID" from the datasheet.  It greatly simplifies the interface to allow
+  only one set of limits (absolute or relative) to be in operation at a
+  time (even though the hardware is capable of enabling both).  There's
+  not a compelling use case for enabling both at once, anyway.  The default
+  is "0,0".
+* vid_agtl: integer
+  A "0" configures the VID pins for V(ih) = 2.1V min, V(il) = 0.8V max.
+  A "1" configures the VID pins for V(ih) = 0.8V min, V(il) = 0.4V max.
+  (The latter setting is referred to as AGTL+ Compatible in the datasheet.)
+  I.e. this parameter controls the VID pin input thresholds; if your VID
+  inputs are not working, try changing this.  The default value is "0".
+
+
+Hardware Description
+--------------------
+
+(from the datasheet)
+
+The LM93 hardware monitor has a two wire digital interface compatible with
+SMBus 2.0. Using an 8-bit ADC, the LM93 measures the temperature of two remote
+diode connected transistors as well as its own die and 16 power supply
+voltages. To set fan speed, the LM93 has two PWM outputs that are each
+controlled by up to four temperature zones. The fancontrol algorithm is lookup
+table based. The LM93 includes a digital filter that can be invoked to smooth
+temperature readings for better control of fan speed. The LM93 has four
+tachometer inputs to measure fan speed. Limit and status registers for all
+measured values are included. The LM93 builds upon the functionality of
+previous motherboard management ASICs and uses some of the LM85's features
+(i.e. smart tachometer mode). It also adds measurement and control support
+for dynamic Vccp monitoring and PROCHOT. It is designed to monitor a dual
+processor Xeon class motherboard with a minimum of external components.
+
+LM94 is also supported in LM93 compatible mode. Extra sensors and features of
+LM94 are not supported.
+
+
+User Interface
+--------------
+
+#PROCHOT
+^^^^^^^^
+
+The LM93 can monitor two #PROCHOT signals.  The results are found in the
+sysfs files prochot1, prochot2, prochot1_avg, prochot2_avg, prochot1_max,
+and prochot2_max.  prochot1_max and prochot2_max contain the user limits
+for #PROCHOT1 and #PROCHOT2, respectively.  prochot1 and prochot2 contain
+the current readings for the most recent complete time interval.  The
+value of prochot1_avg and prochot2_avg is something like a 2 period
+exponential moving average (but not quite - check the datasheet). Note
+that this third value is calculated by the chip itself.  All values range
+from 0-255 where 0 indicates no throttling, and 255 indicates > 99.6%.
+
+The monitoring intervals for the two #PROCHOT signals is also configurable.
+These intervals can be found in the sysfs files prochot1_interval and
+prochot2_interval.  The values in these files specify the intervals for
+#P1_PROCHOT and #P2_PROCHOT, respectively.  Selecting a value not in this
+list will cause the driver to use the next largest interval.  The available
+intervals are (in seconds):
+
+#PROCHOT intervals:
+        0.73, 1.46, 2.9, 5.8, 11.7, 23.3, 46.6, 93.2, 186, 372
+
+It is possible to configure the LM93 to logically short the two #PROCHOT
+signals.  I.e. when #P1_PROCHOT is asserted, the LM93 will automatically
+assert #P2_PROCHOT, and vice-versa.  This mode is enabled by writing a
+non-zero integer to the sysfs file prochot_short.
+
+The LM93 can also override the #PROCHOT pins by driving a PWM signal onto
+one or both of them.  When overridden, the signal has a period of 3.56 ms,
+a minimum pulse width of 5 clocks (at 22.5kHz => 6.25% duty cycle), and
+a maximum pulse width of 80 clocks (at 22.5kHz => 99.88% duty cycle).
+
+The sysfs files prochot1_override and prochot2_override contain boolean
+integers which enable or disable the override function for #P1_PROCHOT and
+#P2_PROCHOT, respectively.  The sysfs file prochot_override_duty_cycle
+contains a value controlling the duty cycle for the PWM signal used when
+the override function is enabled.  This value ranges from 0 to 15, with 0
+indicating minimum duty cycle and 15 indicating maximum.
+
+#VRD_HOT
+^^^^^^^^
+
+The LM93 can monitor two #VRD_HOT signals. The results are found in the
+sysfs files vrdhot1 and vrdhot2. There is one value per file: a boolean for
+which 1 indicates #VRD_HOT is asserted and 0 indicates it is negated. These
+files are read-only.
+
+Smart Tach Mode (from the datasheet)::
+
+        If a fan is driven using a low-side drive PWM, the tachometer
+        output of the fan is corrupted. The LM93 includes smart tachometer
+        circuitry that allows an accurate tachometer reading to be
+        achieved despite the signal corruption.  In smart tach mode all
+        four signals are measured within 4 seconds.
+
+Smart tach mode is enabled by the driver by writing 1 or 2 (associating the
+the fan tachometer with a pwm) to the sysfs file fan<n>_smart_tach.  A zero
+will disable the function for that fan.  Note that Smart tach mode cannot be
+enabled if the PWM output frequency is 22500 Hz (see below).
+
+Manual PWM
+^^^^^^^^^^
+
+The LM93 has a fixed or override mode for the two PWM outputs (although, there
+are still some conditions that will override even this mode - see section
+15.10.6 of the datasheet for details.)  The sysfs files pwm1_override
+and pwm2_override are used to enable this mode; each is a boolean integer
+where 0 disables and 1 enables the manual control mode.  The sysfs files pwm1
+and pwm2 are used to set the manual duty cycle; each is an integer (0-255)
+where 0 is 0% duty cycle, and 255 is 100%.  Note that the duty cycle values
+are constrained by the hardware. Selecting a value which is not available
+will cause the driver to use the next largest value.  Also note: when manual
+PWM mode is disabled, the value of pwm1 and pwm2 indicates the current duty
+cycle chosen by the h/w.
+
+PWM Output Frequency
+^^^^^^^^^^^^^^^^^^^^
+
+The LM93 supports several different frequencies for the PWM output channels.
+The sysfs files pwm1_freq and pwm2_freq are used to select the frequency. The
+frequency values are constrained by the hardware.  Selecting a value which is
+not available will cause the driver to use the next largest value.  Also note
+that this parameter has implications for the Smart Tach Mode (see above).
+
+PWM Output Frequencies (in Hz):
+        12, 36, 48, 60, 72, 84, 96, 22500 (default)
+
+Automatic PWM
+^^^^^^^^^^^^^
+
+The LM93 is capable of complex automatic fan control, with many different
+points of configuration.  To start, each PWM output can be bound to any
+combination of eight control sources.  The final PWM is the largest of all
+individual control sources to which the PWM output is bound.
+
+The eight control sources are: temp1-temp4 (aka "zones" in the datasheet),
+#PROCHOT 1 & 2, and #VRDHOT 1 & 2.  The bindings are expressed as a bitmask
+in the sysfs files pwm<n>_auto_channels, where a "1" enables the binding, and
+a "0" disables it. The h/w default is 0x0f (all temperatures bound).
+
+        ====== ===========
+        0x01   Temp 1
+        0x02   Temp 2
+        0x04   Temp 3
+        0x08   Temp 4
+        0x10   #PROCHOT 1
+        0x20   #PROCHOT 2
+        0x40   #VRDHOT 1
+        0x80   #VRDHOT 2
+        ====== ===========
+
+The function y = f(x) takes a source temperature x to a PWM output y.  This
+function of the LM93 is derived from a base temperature and a table of 12
+temperature offsets.  The base temperature is expressed in degrees C in the
+sysfs files temp<n>_auto_base.  The offsets are expressed in cumulative
+degrees C, with the value of offset <i> for temperature value <n> being
+contained in the file temp<n>_auto_offset<i>.  E.g. if the base temperature
+is 40C:
+
+     ========== ======================= =============== =======
+     offset #   temp<n>_auto_offset<i>  range           pwm
+     ========== ======================= =============== =======
+         1              0               -                25.00%
+         2              0               -                28.57%
+         3              1               40C - 41C        32.14%
+         4              1               41C - 42C        35.71%
+         5              2               42C - 44C        39.29%
+         6              2               44C - 46C        42.86%
+         7              2               48C - 50C        46.43%
+         8              2               50C - 52C        50.00%
+         9              2               52C - 54C        53.57%
+        10              2               54C - 56C        57.14%
+        11              2               56C - 58C        71.43%
+        12              2               58C - 60C        85.71%
+        -               -               > 60C           100.00%
+     ========== ======================= =============== =======
+
+Valid offsets are in the range 0C <= x <= 7.5C in 0.5C increments.
+
+There is an independent base temperature for each temperature channel. Note,
+however, there are only two tables of offsets: one each for temp[12] and
+temp[34].  Therefore, any change to e.g. temp1_auto_offset<i> will also
+affect temp2_auto_offset<i>.
+
+The LM93 can also apply hysteresis to the offset table, to prevent unwanted
+oscillation between two steps in the offsets table.  These values are found in
+the sysfs files temp<n>_auto_offset_hyst.  The value in this file has the
+same representation as in temp<n>_auto_offset<i>.
+
+If a temperature reading falls below the base value for that channel, the LM93
+will use the minimum PWM value.  These values are found in the sysfs files
+temp<n>_auto_pwm_min.  Note, there are only two minimums: one each for temp[12]
+and temp[34].  Therefore, any change to e.g. temp1_auto_pwm_min will also
+affect temp2_auto_pwm_min.
+
+PWM Spin-Up Cycle
+^^^^^^^^^^^^^^^^^
+
+A spin-up cycle occurs when a PWM output is commanded from 0% duty cycle to
+some value > 0%.  The LM93 supports a minimum duty cycle during spin-up.  These
+values are found in the sysfs files pwm<n>_auto_spinup_min. The value in this
+file has the same representation as other PWM duty cycle values. The
+duration of the spin-up cycle is also configurable.  These values are found in
+the sysfs files pwm<n>_auto_spinup_time. The value in this file is
+the spin-up time in seconds.  The available spin-up times are constrained by
+the hardware.  Selecting a value which is not available will cause the driver
+to use the next largest value.
+
+Spin-up Durations:
+        0 (disabled, h/w default), 0.1, 0.25, 0.4, 0.7, 1.0, 2.0, 4.0
+
+#PROCHOT and #VRDHOT PWM Ramping
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+If the #PROCHOT or #VRDHOT signals are asserted while bound to a PWM output
+channel, the LM93 will ramp the PWM output up to 100% duty cycle in discrete
+steps. The duration of each step is configurable. There are two files, with
+one value each in seconds: pwm_auto_prochot_ramp and pwm_auto_vrdhot_ramp.
+The available ramp times are constrained by the hardware.  Selecting a value
+which is not available will cause the driver to use the next largest value.
+
+Ramp Times:
+        0 (disabled, h/w default) to 0.75 in 0.05 second intervals
+
+Fan Boost
+^^^^^^^^^
+
+For each temperature channel, there is a boost temperature: if the channel
+exceeds this limit, the LM93 will immediately drive both PWM outputs to 100%.
+This limit is expressed in degrees C in the sysfs files temp<n>_auto_boost.
+There is also a hysteresis temperature for this function: after the boost
+limit is reached, the temperature channel must drop below this value before
+the boost function is disabled.  This temperature is also expressed in degrees
+C in the sysfs files temp<n>_auto_boost_hyst.
+
+GPIO Pins
+^^^^^^^^^
+
+The LM93 can monitor the logic level of four dedicated GPIO pins as well as the
+four tach input pins.  GPIO0-GPIO3 correspond to (fan) tach 1-4, respectively.
+All eight GPIOs are read by reading the bitmask in the sysfs file gpio.  The
+LSB is GPIO0, and the MSB is GPIO7.
+
+
+LM93 Unique sysfs Files
+-----------------------
+
+=========================== ===============================================
+file                        description
+=========================== ===============================================
+prochot<n>                  current #PROCHOT %
+prochot<n>_avg              moving average #PROCHOT %
+prochot<n>_max              limit #PROCHOT %
+prochot_short               enable or disable logical #PROCHOT pin short
+prochot<n>_override         force #PROCHOT assertion as PWM
+prochot_override_duty_cycle duty cycle for the PWM signal used when
+                            #PROCHOT is overridden
+prochot<n>_interval         #PROCHOT PWM sampling interval
+vrdhot<n>                   0 means negated, 1 means asserted
+fan<n>_smart_tach           enable or disable smart tach mode
+pwm<n>_auto_channels        select control sources for PWM outputs
+pwm<n>_auto_spinup_min      minimum duty cycle during spin-up
+pwm<n>_auto_spinup_time     duration of spin-up
+pwm_auto_prochot_ramp       ramp time per step when #PROCHOT asserted
+pwm_auto_vrdhot_ramp        ramp time per step when #VRDHOT asserted
+temp<n>_auto_base           temperature channel base
+temp<n>_auto_offset[1-12]   temperature channel offsets
+temp<n>_auto_offset_hyst    temperature channel offset hysteresis
+temp<n>_auto_boost          temperature channel boost (PWMs to 100%)
+                            limit
+temp<n>_auto_boost_hyst     temperature channel boost hysteresis
+gpio                        input state of 8 GPIO pins; read-only
+=========================== ===============================================