Commit b825037d authored by Juerg Haefliger's avatar Juerg Haefliger Committed by Mark M. Hoffman
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hwmon/dme1737: Add documentation

Add documentation for the new SMSC DME1737 driver.

Signed-off-by: Juerg Haefliger <juergh at>
Signed-off-by: default avatarJean Delvare <>
parent 9431996f
Kernel driver dme1737
Supported chips:
* SMSC DME1737 and compatibles (like Asus A8000)
Prefix: 'dme1737'
Addresses scanned: I2C 0x2c, 0x2d, 0x2e
Datasheet: Provided by SMSC upon request and under NDA
Juerg Haefliger <>
Module Parameters
* force_start: bool Enables the monitoring of voltage, fan and temp inputs
and PWM output control functions. Using this parameter
shouldn't be required since the BIOS usually takes care
of this.
Note that there is no need to use this parameter if the driver loads without
complaining. The driver will say so if it is necessary.
This driver implements support for the hardware monitoring capabilities of the
SMSC DME1737 and Asus A8000 (which are the same) Super-I/O chips. This chip
features monitoring of 3 temp sensors temp[1-3] (2 remote diodes and 1
internal), 7 voltages in[0-6] (6 external and 1 internal) and 6 fan speeds
fan[1-6]. Additionally, the chip implements 5 PWM outputs pwm[1-3,5-6] for
controlling fan speeds both manually and automatically.
Fan[3-6] and pwm[3,5-6] are optional features and their availability is
dependent on the configuration of the chip. The driver will detect which
features are present during initialization and create the sysfs attributes
Voltage Monitoring
The voltage inputs are sampled with 12-bit resolution and have internal
scaling resistors. The values returned by the driver therefore reflect true
millivolts and don't need scaling. The voltage inputs are mapped as follows
(the last column indicates the input ranges):
in0: +5VTR (+5V standby) 0V - 6.64V
in1: Vccp (processor core) 0V - 3V
in2: VCC (internal +3.3V) 0V - 4.38V
in3: +5V 0V - 6.64V
in4: +12V 0V - 16V
in5: VTR (+3.3V standby) 0V - 4.38V
in6: Vbat (+3.0V) 0V - 4.38V
Each voltage input has associated min and max limits which trigger an alarm
when crossed.
Temperature Monitoring
Temperatures are measured with 12-bit resolution and reported in millidegree
Celsius. The chip also features offsets for all 3 temperature inputs which -
when programmed - get added to the input readings. The chip does all the
scaling by itself and the driver therefore reports true temperatures that don't
need any user-space adjustments. The temperature inputs are mapped as follows
(the last column indicates the input ranges):
temp1: Remote diode 1 (3904 type) temperature -127C - +127C
temp2: DME1737 internal temperature -127C - +127C
temp3: Remote diode 2 (3904 type) temperature -127C - +127C
Each temperature input has associated min and max limits which trigger an alarm
when crossed. Additionally, each temperature input has a fault attribute that
returns 1 when a faulty diode or an unconnected input is detected and 0
Fan Monitoring
Fan RPMs are measured with 16-bit resolution. The chip provides inputs for 6
fan tachometers. All 6 inputs have an associated min limit which triggers an
alarm when crossed. Fan inputs 1-4 provide type attributes that need to be set
to the number of pulses per fan revolution that the connected tachometer
generates. Supported values are 1, 2, and 4. Fan inputs 5-6 only support fans
that generate 2 pulses per revolution. Fan inputs 5-6 also provide a max
attribute that needs to be set to the maximum attainable RPM (fan at 100% duty-
cycle) of the input. The chip adjusts the sampling rate based on this value.
PWM Output Control
This chip features 5 PWM outputs. PWM outputs 1-3 are associated with fan
inputs 1-3 and PWM outputs 5-6 are associated with fan inputs 5-6. PWM outputs
1-3 can be configured to operate either in manual or automatic mode by setting
the appropriate enable attribute accordingly. PWM outputs 5-6 can only operate
in manual mode, their enable attributes are therefore read-only. When set to
manual mode, the fan speed is set by writing the duty-cycle value to the
appropriate PWM attribute. In automatic mode, the PWM attribute returns the
current duty-cycle as set by the fan controller in the chip. All PWM outputs
support the setting of the output frequency via the freq attribute.
In automatic mode, the chip supports the setting of the PWM ramp rate which
defines how fast the PWM output is adjusting to changes of the associated
temperature input. Associating PWM outputs to temperature inputs is done via
temperature zones. The chip features 3 zones whose assignments to temperature
inputs is static and determined during initialization. These assignments can
be retrieved via the zone[1-3]_auto_channels_temp attributes. Each PWM output
is assigned to one (or hottest of multiple) temperature zone(s) through the
pwm[1-3]_auto_channels_zone attributes. Each PWM output has 3 distinct output
duty-cycles: full, low, and min. Full is internally hard-wired to 255 (100%)
and low and min can be programmed via pwm[1-3]_auto_point1_pwm and
pwm[1-3]_auto_pwm_min, respectively. The thermal thresholds of the zones are
programmed via zone[1-3]_auto_point[1-3]_temp and
pwm[1-3]_auto_point2_pwm full-speed duty-cycle (255, i.e., 100%)
pwm[1-3]_auto_point1_pwm low-speed duty-cycle
pwm[1-3]_auto_pwm_min min-speed duty-cycle
zone[1-3]_auto_point3_temp full-speed temp (all outputs)
zone[1-3]_auto_point2_temp full-speed temp
zone[1-3]_auto_point1_temp low-speed temp
zone[1-3]_auto_point1_temp_hyst min-speed temp
The chip adjusts the output duty-cycle linearly in the range of auto_point1_pwm
to auto_point2_pwm if the temperature of the associated zone is between
auto_point1_temp and auto_point2_temp. If the temperature drops below the
auto_point1_temp_hyst value, the output duty-cycle is set to the auto_pwm_min
value which only supports two values: 0 or auto_point1_pwm. That means that the
fan either turns completely off or keeps spinning with the low-speed
duty-cycle. If any of the temperatures rise above the auto_point3_temp value,
all PWM outputs are set to 100% duty-cycle.
Following is another representation of how the chip sets the output duty-cycle
based on the temperature of the associated thermal zone:
Duty-Cycle Duty-Cycle
Temperature Rising Temp Falling Temp
----------- ----------- ------------
full-speed full-speed full-speed
< linearly adjusted duty-cycle >
low-speed low-speed low-speed
min-speed low-speed
min-speed min-speed min-speed
min-speed min-speed
Sysfs Attributes
Following is a list of all sysfs attributes that the driver provides, their
permissions and a short description:
Name Perm Description
---- ---- -----------
cpu0_vid RO CPU core reference voltage in
vrm RW Voltage regulator module version
in[0-6]_input RO Measured voltage in millivolts.
in[0-6]_min RW Low limit for voltage input.
in[0-6]_max RW High limit for voltage input.
in[0-6]_alarm RO Voltage input alarm. Returns 1 if
voltage input is or went outside the
associated min-max range, 0 otherwise.
temp[1-3]_input RO Measured temperature in millidegree
temp[1-3]_min RW Low limit for temp input.
temp[1-3]_max RW High limit for temp input.
temp[1-3]_offset RW Offset for temp input. This value will
be added by the chip to the measured
temp[1-3]_alarm RO Alarm for temp input. Returns 1 if temp
input is or went outside the associated
min-max range, 0 otherwise.
temp[1-3]_fault RO Temp input fault. Returns 1 if the chip
detects a faulty thermal diode or an
unconnected temp input, 0 otherwise.
zone[1-3]_auto_channels_temp RO Temperature zone to temperature input
mapping. This attribute is a bitfield
and supports the following values:
1: temp1
2: temp2
4: temp3
zone[1-3]_auto_point1_temp_hyst RW Auto PWM temp point1 hysteresis. The
output of the corresponding PWM is set
to the pwm_auto_min value if the temp
falls below the auto_point1_temp_hyst
zone[1-3]_auto_point[1-3]_temp RW Auto PWM temp points. Auto_point1 is
the low-speed temp, auto_point2 is the
full-speed temp, and auto_point3 is the
temp at which all PWM outputs are set
to full-speed (100% duty-cycle).
fan[1-6]_input RO Measured fan speed in RPM.
fan[1-6]_min RW Low limit for fan input.
fan[1-6]_alarm RO Alarm for fan input. Returns 1 if fan
input is or went below the associated
min value, 0 otherwise.
fan[1-4]_type RW Type of attached fan. Expressed in
number of pulses per revolution that
the fan generates. Supported values are
1, 2, and 4.
fan[5-6]_max RW Max attainable RPM at 100% duty-cycle.
Required for chip to adjust the
sampling rate accordingly.
pmw[1-3,5-6] RO/RW Duty-cycle of PWM output. Supported
values are 0-255 (0%-100%). Only
writeable if the associated PWM is in
manual mode.
pwm[1-3]_enable RW Enable of PWM outputs 1-3. Supported
values are:
0: turned off (output @ 100%)
1: manual mode
2: automatic mode
pwm[5-6]_enable RO Enable of PWM outputs 5-6. Always
returns 1 since these 2 outputs are
hard-wired to manual mode.
pmw[1-3,5-6]_freq RW Frequency of PWM output. Supported
values are in the range 11Hz-30000Hz
(default is 25000Hz).
pmw[1-3]_ramp_rate RW Ramp rate of PWM output. Determines how
fast the PWM duty-cycle will change
when the PWM is in automatic mode.
Expressed in ms per PWM step. Supported
values are in the range 0ms-206ms
(default is 0, which means the duty-
cycle changes instantly).
pwm[1-3]_auto_channels_zone RW PWM output to temperature zone mapping.
This attribute is a bitfield and
supports the following values:
1: zone1
2: zone2
4: zone3
6: highest of zone[2-3]
7: highest of zone[1-3]
pwm[1-3]_auto_pwm_min RW Auto PWM min pwm. Minimum PWM duty-
cycle. Supported values are 0 or
pwm[1-3]_auto_point1_pwm RW Auto PWM pwm point. Auto_point1 is the
low-speed duty-cycle.
pwm[1-3]_auto_point2_pwm RO Auto PWM pwm point. Auto_point2 is the
full-speed duty-cycle which is hard-
wired to 255 (100% duty-cycle).
......@@ -1283,6 +1283,12 @@ M:
S: Maintained
P: Juerg Haefliger
S: Maintained
P: Randy Dunlap
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