Documentation/hwmon/lm93 - kernel/msm-4.9 - Gitiles

 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

 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.


 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
	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

	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.


	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