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  * Nuvoton NCT6793D
36    Prefix: 'nct6793'
37    Addresses scanned: ISA address retrieved from Super I/O registers
38    Datasheet: Available from Nuvoton upon request
39
40Authors:
41        Guenter Roeck <linux@roeck-us.net>
42
43Description
44-----------
45
46This driver implements support for the Nuvoton NCT6775F, NCT6776F, and NCT6779D
47and compatible super I/O chips.
48
49The chips support up to 25 temperature monitoring sources. Up to 6 of those are
50direct temperature sensor inputs, the others are special sources such as PECI,
51PCH, and SMBUS. Depending on the chip type, 2 to 6 of the temperature sources
52can be monitored and compared against minimum, maximum, and critical
53temperatures. The driver reports up to 10 of the temperatures to the user.
54There are 4 to 5 fan rotation speed sensors, 8 to 15 analog voltage sensors,
55one VID, alarms with beep warnings (control unimplemented), and some automatic
56fan regulation strategies (plus manual fan control mode).
57
58The temperature sensor sources on all chips are configurable. The configured
59source for each of the temperature sensors is provided in tempX_label.
60
61Temperatures are measured in degrees Celsius and measurement resolution is
62either 1 degC or 0.5 degC, depending on the temperature source and
63configuration. An alarm is triggered when the temperature gets higher than
64the high limit; it stays on until the temperature falls below the hysteresis
65value. Alarms are only supported for temp1 to temp6, depending on the chip type.
66
67Fan rotation speeds are reported in RPM (rotations per minute). An alarm is
68triggered if the rotation speed has dropped below a programmable limit. On
69NCT6775F, fan readings can be divided by a programmable divider (1, 2, 4, 8,
7016, 32, 64 or 128) to give the readings more range or accuracy; the other chips
71do not have a fan speed divider. The driver sets the most suitable fan divisor
72itself; specifically, it increases the divider value each time a fan speed
73reading returns an invalid value, and it reduces it if the fan speed reading
74is lower than optimal. Some fans might not be present because they share pins
75with other functions.
76
77Voltage sensors (also known as IN sensors) report their values in millivolts.
78An alarm is triggered if the voltage has crossed a programmable minimum
79or maximum limit.
80
81The driver supports automatic fan control mode known as Thermal Cruise.
82In this mode, the chip attempts to keep the measured temperature in a
83predefined temperature range. If the temperature goes out of range, fan
84is driven slower/faster to reach the predefined range again.
85
86The mode works for fan1-fan5.
87
88sysfs attributes
89----------------
90
91pwm[1-5] - this file stores PWM duty cycle or DC value (fan speed) in range:
92	   0 (lowest speed) to 255 (full)
93
94pwm[1-5]_enable - this file controls mode of fan/temperature control:
95	* 0 Fan control disabled (fans set to maximum speed)
96	* 1 Manual mode, write to pwm[0-5] any value 0-255
97	* 2 "Thermal Cruise" mode
98	* 3 "Fan Speed Cruise" mode
99	* 4 "Smart Fan III" mode (NCT6775F only)
100	* 5 "Smart Fan IV" mode
101
102pwm[1-5]_mode - controls if output is PWM or DC level
103        * 0 DC output
104        * 1 PWM output
105
106Common fan control attributes
107-----------------------------
108
109pwm[1-5]_temp_sel	Temperature source. Value is temperature sensor index.
110			For example, select '1' for temp1_input.
111pwm[1-5]_weight_temp_sel
112			Secondary temperature source. Value is temperature
113			sensor index. For example, select '1' for temp1_input.
114			Set to 0 to disable secondary temperature control.
115
116If secondary temperature functionality is enabled, it is controlled with the
117following attributes.
118
119pwm[1-5]_weight_duty_step
120			Duty step size.
121pwm[1-5]_weight_temp_step
122			Temperature step size. With each step over
123			temp_step_base, the value of weight_duty_step is added
124			to the current pwm value.
125pwm[1-5]_weight_temp_step_base
126			Temperature at which secondary temperature control kicks
127			in.
128pwm[1-5]_weight_temp_step_tol
129			Temperature step tolerance.
130
131Thermal Cruise mode (2)
132-----------------------
133
134If the temperature is in the range defined by:
135
136pwm[1-5]_target_temp	Target temperature, unit millidegree Celsius
137			(range 0 - 127000)
138pwm[1-5]_temp_tolerance
139			Target temperature tolerance, unit millidegree Celsius
140
141there are no changes to fan speed. Once the temperature leaves the interval, fan
142speed increases (if temperature is higher that desired) or decreases (if
143temperature is lower than desired), using the following limits and time
144intervals.
145
146pwm[1-5]_start		fan pwm start value (range 1 - 255), to start fan
147			when the temperature is above defined range.
148pwm[1-5]_floor		lowest fan pwm (range 0 - 255) if temperature is below
149			the defined range. If set to 0, the fan is expected to
150			stop if the temperature is below the defined range.
151pwm[1-5]_step_up_time	milliseconds before fan speed is increased
152pwm[1-5]_step_down_time	milliseconds before fan speed is decreased
153pwm[1-5]_stop_time	how many milliseconds must elapse to switch
154			corresponding fan off (when the temperature was below
155			defined range).
156
157Speed Cruise mode (3)
158---------------------
159
160This modes tries to keep the fan speed constant.
161
162fan[1-5]_target		Target fan speed
163fan[1-5]_tolerance
164			Target speed tolerance
165
166
167Untested; use at your own risk.
168
169Smart Fan IV mode (5)
170---------------------
171
172This mode offers multiple slopes to control the fan speed. The slopes can be
173controlled by setting the pwm and temperature attributes. When the temperature
174rises, the chip will calculate the DC/PWM output based on the current slope.
175There are up to seven data points depending on the chip type. Subsequent data
176points should be set to higher temperatures and higher pwm values to achieve
177higher fan speeds with increasing temperature. The last data point reflects
178critical temperature mode, in which the fans should run at full speed.
179
180pwm[1-5]_auto_point[1-7]_pwm
181			pwm value to be set if temperature reaches matching
182			temperature range.
183pwm[1-5]_auto_point[1-7]_temp
184			Temperature over which the matching pwm is enabled.
185pwm[1-5]_temp_tolerance
186			Temperature tolerance, unit millidegree Celsius
187pwm[1-5]_crit_temp_tolerance
188			Temperature tolerance for critical temperature,
189			unit millidegree Celsius
190
191pwm[1-5]_step_up_time	milliseconds before fan speed is increased
192pwm[1-5]_step_down_time	milliseconds before fan speed is decreased
193
194Usage Notes
195-----------
196
197On various ASUS boards with NCT6776F, it appears that CPUTIN is not really
198connected to anything and floats, or that it is connected to some non-standard
199temperature measurement device. As a result, the temperature reported on CPUTIN
200will not reflect a usable value. It often reports unreasonably high
201temperatures, and in some cases the reported temperature declines if the actual
202temperature increases (similar to the raw PECI temperature value - see PECI
203specification for details). CPUTIN should therefore be be ignored on ASUS
204boards. The CPU temperature on ASUS boards is reported from PECI 0.
205