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+Kernel driver lm93
+ * 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
+ Mark M. Hoffman <firstname.lastname@example.org>
+ Ported to 2.6 by Eric J. Bowersox <email@example.com>
+ Adapted to 2.6.20 by Carsten Emde <firstname.lastname@example.org>
+ Modified for mainline integration by Hans J. Koch <email@example.com>
+* 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".
+(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.
+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.
+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).
+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)
+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
+ 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 and
+temp. Therefore, any change to e.g. temp1_auto_offset<i> will also
+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
+and temp. Therefore, any change to e.g. temp1_auto_pwm_min will also
+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
+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.
+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
+ 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
+ temperature channel offsets
+ 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