1Note
2====
3
4This driver supersedes the NCT6775F and NCT6776F support in the W83627EHF
5driver.
6
7Kernel driver NCT6775
8=====================
9
10Supported chips:
11  * Nuvoton NCT6102D/NCT6104D/NCT6106D
12    Prefix: 'nct6106'
13    Addresses scanned: ISA address retrieved from Super I/O registers
14    Datasheet: Available from the Nuvoton web site
15  * Nuvoton NCT5572D/NCT6771F/NCT6772F/NCT6775F/W83677HG-I
16    Prefix: 'nct6775'
17    Addresses scanned: ISA address retrieved from Super I/O registers
18    Datasheet: Available from Nuvoton upon request
19  * Nuvoton NCT5573D/NCT5577D/NCT6776D/NCT6776F
20    Prefix: 'nct6776'
21    Addresses scanned: ISA address retrieved from Super I/O registers
22    Datasheet: Available from Nuvoton upon request
23  * Nuvoton NCT5532D/NCT6779D
24    Prefix: 'nct6779'
25    Addresses scanned: ISA address retrieved from Super I/O registers
26    Datasheet: Available from Nuvoton upon request
27  * Nuvoton NCT6791D
28    Prefix: 'nct6791'
29    Addresses scanned: ISA address retrieved from Super I/O registers
30    Datasheet: Available from Nuvoton upon request
31  * Nuvoton NCT6792D
32    Prefix: 'nct6792'
33    Addresses scanned: ISA address retrieved from Super I/O registers
34    Datasheet: Available from Nuvoton upon request
35
36Authors:
37        Guenter Roeck <linux@roeck-us.net>
38
39Description
40-----------
41
42This driver implements support for the Nuvoton NCT6775F, NCT6776F, and NCT6779D
43and compatible super I/O chips.
44
45The chips support up to 25 temperature monitoring sources. Up to 6 of those are
46direct temperature sensor inputs, the others are special sources such as PECI,
47PCH, and SMBUS. Depending on the chip type, 2 to 6 of the temperature sources
48can be monitored and compared against minimum, maximum, and critical
49temperatures. The driver reports up to 10 of the temperatures to the user.
50There are 4 to 5 fan rotation speed sensors, 8 to 15 analog voltage sensors,
51one VID, alarms with beep warnings (control unimplemented), and some automatic
52fan regulation strategies (plus manual fan control mode).
53
54The temperature sensor sources on all chips are configurable. The configured
55source for each of the temperature sensors is provided in tempX_label.
56
57Temperatures are measured in degrees Celsius and measurement resolution is
58either 1 degC or 0.5 degC, depending on the temperature source and
59configuration. An alarm is triggered when the temperature gets higher than
60the high limit; it stays on until the temperature falls below the hysteresis
61value. Alarms are only supported for temp1 to temp6, depending on the chip type.
62
63Fan rotation speeds are reported in RPM (rotations per minute). An alarm is
64triggered if the rotation speed has dropped below a programmable limit. On
65NCT6775F, fan readings can be divided by a programmable divider (1, 2, 4, 8,
6616, 32, 64 or 128) to give the readings more range or accuracy; the other chips
67do not have a fan speed divider. The driver sets the most suitable fan divisor
68itself; specifically, it increases the divider value each time a fan speed
69reading returns an invalid value, and it reduces it if the fan speed reading
70is lower than optimal. Some fans might not be present because they share pins
71with other functions.
72
73Voltage sensors (also known as IN sensors) report their values in millivolts.
74An alarm is triggered if the voltage has crossed a programmable minimum
75or maximum limit.
76
77The driver supports automatic fan control mode known as Thermal Cruise.
78In this mode, the chip attempts to keep the measured temperature in a
79predefined temperature range. If the temperature goes out of range, fan
80is driven slower/faster to reach the predefined range again.
81
82The mode works for fan1-fan5.
83
84sysfs attributes
85----------------
86
87pwm[1-5] - this file stores PWM duty cycle or DC value (fan speed) in range:
88	   0 (lowest speed) to 255 (full)
89
90pwm[1-5]_enable - this file controls mode of fan/temperature control:
91	* 0 Fan control disabled (fans set to maximum speed)
92	* 1 Manual mode, write to pwm[0-5] any value 0-255
93	* 2 "Thermal Cruise" mode
94	* 3 "Fan Speed Cruise" mode
95	* 4 "Smart Fan III" mode (NCT6775F only)
96	* 5 "Smart Fan IV" mode
97
98pwm[1-5]_mode - controls if output is PWM or DC level
99        * 0 DC output
100        * 1 PWM output
101
102Common fan control attributes
103-----------------------------
104
105pwm[1-5]_temp_sel	Temperature source. Value is temperature sensor index.
106			For example, select '1' for temp1_input.
107pwm[1-5]_weight_temp_sel
108			Secondary temperature source. Value is temperature
109			sensor index. For example, select '1' for temp1_input.
110			Set to 0 to disable secondary temperature control.
111
112If secondary temperature functionality is enabled, it is controlled with the
113following attributes.
114
115pwm[1-5]_weight_duty_step
116			Duty step size.
117pwm[1-5]_weight_temp_step
118			Temperature step size. With each step over
119			temp_step_base, the value of weight_duty_step is added
120			to the current pwm value.
121pwm[1-5]_weight_temp_step_base
122			Temperature at which secondary temperature control kicks
123			in.
124pwm[1-5]_weight_temp_step_tol
125			Temperature step tolerance.
126
127Thermal Cruise mode (2)
128-----------------------
129
130If the temperature is in the range defined by:
131
132pwm[1-5]_target_temp	Target temperature, unit millidegree Celsius
133			(range 0 - 127000)
134pwm[1-5]_temp_tolerance
135			Target temperature tolerance, unit millidegree Celsius
136
137there are no changes to fan speed. Once the temperature leaves the interval, fan
138speed increases (if temperature is higher that desired) or decreases (if
139temperature is lower than desired), using the following limits and time
140intervals.
141
142pwm[1-5]_start		fan pwm start value (range 1 - 255), to start fan
143			when the temperature is above defined range.
144pwm[1-5]_floor		lowest fan pwm (range 0 - 255) if temperature is below
145			the defined range. If set to 0, the fan is expected to
146			stop if the temperature is below the defined range.
147pwm[1-5]_step_up_time	milliseconds before fan speed is increased
148pwm[1-5]_step_down_time	milliseconds before fan speed is decreased
149pwm[1-5]_stop_time	how many milliseconds must elapse to switch
150			corresponding fan off (when the temperature was below
151			defined range).
152
153Speed Cruise mode (3)
154---------------------
155
156This modes tries to keep the fan speed constant.
157
158fan[1-5]_target		Target fan speed
159fan[1-5]_tolerance
160			Target speed tolerance
161
162
163Untested; use at your own risk.
164
165Smart Fan IV mode (5)
166---------------------
167
168This mode offers multiple slopes to control the fan speed. The slopes can be
169controlled by setting the pwm and temperature attributes. When the temperature
170rises, the chip will calculate the DC/PWM output based on the current slope.
171There are up to seven data points depending on the chip type. Subsequent data
172points should be set to higher temperatures and higher pwm values to achieve
173higher fan speeds with increasing temperature. The last data point reflects
174critical temperature mode, in which the fans should run at full speed.
175
176pwm[1-5]_auto_point[1-7]_pwm
177			pwm value to be set if temperature reaches matching
178			temperature range.
179pwm[1-5]_auto_point[1-7]_temp
180			Temperature over which the matching pwm is enabled.
181pwm[1-5]_temp_tolerance
182			Temperature tolerance, unit millidegree Celsius
183pwm[1-5]_crit_temp_tolerance
184			Temperature tolerance for critical temperature,
185			unit millidegree Celsius
186
187pwm[1-5]_step_up_time	milliseconds before fan speed is increased
188pwm[1-5]_step_down_time	milliseconds before fan speed is decreased
189
190Usage Notes
191-----------
192
193On various ASUS boards with NCT6776F, it appears that CPUTIN is not really
194connected to anything and floats, or that it is connected to some non-standard
195temperature measurement device. As a result, the temperature reported on CPUTIN
196will not reflect a usable value. It often reports unreasonably high
197temperatures, and in some cases the reported temperature declines if the actual
198temperature increases (similar to the raw PECI temperature value - see PECI
199specification for details). CPUTIN should therefore be be ignored on ASUS
200boards. The CPU temperature on ASUS boards is reported from PECI 0.
201