tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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 NCT5572D/NCT6771F/NCT6772F/NCT6775F/W83677HG-I
12 Prefix: 'nct6775'
13 Addresses scanned: ISA address retrieved from Super I/O registers
14 Datasheet: Available from Nuvoton upon request
15 * Nuvoton NCT5577D/NCT6776D/NCT6776F
16 Prefix: 'nct6776'
17 Addresses scanned: ISA address retrieved from Super I/O registers
18 Datasheet: Available from Nuvoton upon request
19 * Nuvoton NCT5532D/NCT6779D
20 Prefix: 'nct6779'
21 Addresses scanned: ISA address retrieved from Super I/O registers
22 Datasheet: Available from Nuvoton upon request
23
24Authors:
25 Guenter Roeck <linux@roeck-us.net>
26
27Description
28-----------
29
30This driver implements support for the Nuvoton NCT6775F, NCT6776F, and NCT6779D
31and compatible super I/O chips.
32
33The chips support up to 25 temperature monitoring sources. Up to 6 of those are
34direct temperature sensor inputs, the others are special sources such as PECI,
35PCH, and SMBUS. Depending on the chip type, 2 to 6 of the temperature sources
36can be monitored and compared against minimum, maximum, and critical
37temperatures. The driver reports up to 10 of the temperatures to the user.
38There are 4 to 5 fan rotation speed sensors, 8 to 15 analog voltage sensors,
39one VID, alarms with beep warnings (control unimplemented), and some automatic
40fan regulation strategies (plus manual fan control mode).
41
42The temperature sensor sources on all chips are configurable. The configured
43source for each of the temperature sensors is provided in tempX_label.
44
45Temperatures are measured in degrees Celsius and measurement resolution is
46either 1 degC or 0.5 degC, depending on the temperature source and
47configuration. An alarm is triggered when the temperature gets higher than
48the high limit; it stays on until the temperature falls below the hysteresis
49value. Alarms are only supported for temp1 to temp6, depending on the chip type.
50
51Fan rotation speeds are reported in RPM (rotations per minute). An alarm is
52triggered if the rotation speed has dropped below a programmable limit. On
53NCT6775F, fan readings can be divided by a programmable divider (1, 2, 4, 8,
5416, 32, 64 or 128) to give the readings more range or accuracy; the other chips
55do not have a fan speed divider. The driver sets the most suitable fan divisor
56itself; specifically, it increases the divider value each time a fan speed
57reading returns an invalid value, and it reduces it if the fan speed reading
58is lower than optimal. Some fans might not be present because they share pins
59with other functions.
60
61Voltage sensors (also known as IN sensors) report their values in millivolts.
62An alarm is triggered if the voltage has crossed a programmable minimum
63or maximum limit.
64
65The driver supports automatic fan control mode known as Thermal Cruise.
66In this mode, the chip attempts to keep the measured temperature in a
67predefined temperature range. If the temperature goes out of range, fan
68is driven slower/faster to reach the predefined range again.
69
70The mode works for fan1-fan5.
71
72sysfs attributes
73----------------
74
75pwm[1-5] - this file stores PWM duty cycle or DC value (fan speed) in range:
76 0 (lowest speed) to 255 (full)
77
78pwm[1-5]_enable - this file controls mode of fan/temperature control:
79 * 0 Fan control disabled (fans set to maximum speed)
80 * 1 Manual mode, write to pwm[0-5] any value 0-255
81 * 2 "Thermal Cruise" mode
82 * 3 "Fan Speed Cruise" mode
83 * 4 "Smart Fan III" mode (NCT6775F only)
84 * 5 "Smart Fan IV" mode
85
86pwm[1-5]_mode - controls if output is PWM or DC level
87 * 0 DC output
88 * 1 PWM output
89
90Common fan control attributes
91-----------------------------
92
93pwm[1-5]_temp_sel Temperature source. Value is temperature sensor index.
94 For example, select '1' for temp1_input.
95pwm[1-5]_weight_temp_sel
96 Secondary temperature source. Value is temperature
97 sensor index. For example, select '1' for temp1_input.
98 Set to 0 to disable secondary temperature control.
99
100If secondary temperature functionality is enabled, it is controlled with the
101following attributes.
102
103pwm[1-5]_weight_duty_step
104 Duty step size.
105pwm[1-5]_weight_temp_step
106 Temperature step size. With each step over
107 temp_step_base, the value of weight_duty_step is added
108 to the current pwm value.
109pwm[1-5]_weight_temp_step_base
110 Temperature at which secondary temperature control kicks
111 in.
112pwm[1-5]_weight_temp_step_tol
113 Temperature step tolerance.
114
115Thermal Cruise mode (2)
116-----------------------
117
118If the temperature is in the range defined by:
119
120pwm[1-5]_target_temp Target temperature, unit millidegree Celsius
121 (range 0 - 127000)
122pwm[1-5]_temp_tolerance
123 Target temperature tolerance, unit millidegree Celsius
124
125there are no changes to fan speed. Once the temperature leaves the interval, fan
126speed increases (if temperature is higher that desired) or decreases (if
127temperature is lower than desired), using the following limits and time
128intervals.
129
130pwm[1-5]_start fan pwm start value (range 1 - 255), to start fan
131 when the temperature is above defined range.
132pwm[1-5]_floor lowest fan pwm (range 0 - 255) if temperature is below
133 the defined range. If set to 0, the fan is expected to
134 stop if the temperature is below the defined range.
135pwm[1-5]_step_up_time milliseconds before fan speed is increased
136pwm[1-5]_step_down_time milliseconds before fan speed is decreased
137pwm[1-5]_stop_time how many milliseconds must elapse to switch
138 corresponding fan off (when the temperature was below
139 defined range).
140
141Speed Cruise mode (3)
142---------------------
143
144This modes tries to keep the fan speed constant.
145
146fan[1-5]_target Target fan speed
147fan[1-5]_tolerance
148 Target speed tolerance
149
150
151Untested; use at your own risk.
152
153Smart Fan IV mode (5)
154---------------------
155
156This mode offers multiple slopes to control the fan speed. The slopes can be
157controlled by setting the pwm and temperature attributes. When the temperature
158rises, the chip will calculate the DC/PWM output based on the current slope.
159There are up to seven data points depending on the chip type. Subsequent data
160points should be set to higher temperatures and higher pwm values to achieve
161higher fan speeds with increasing temperature. The last data point reflects
162critical temperature mode, in which the fans should run at full speed.
163
164pwm[1-5]_auto_point[1-7]_pwm
165 pwm value to be set if temperature reaches matching
166 temperature range.
167pwm[1-5]_auto_point[1-7]_temp
168 Temperature over which the matching pwm is enabled.
169pwm[1-5]_temp_tolerance
170 Temperature tolerance, unit millidegree Celsius
171pwm[1-5]_crit_temp_tolerance
172 Temperature tolerance for critical temperature,
173 unit millidegree Celsius
174
175pwm[1-5]_step_up_time milliseconds before fan speed is increased
176pwm[1-5]_step_down_time milliseconds before fan speed is decreased
177
178Usage Notes
179-----------
180
181On various ASUS boards with NCT6776F, it appears that CPUTIN is not really
182connected to anything and floats, or that it is connected to some non-standard
183temperature measurement device. As a result, the temperature reported on CPUTIN
184will not reflect a usable value. It often reports unreasonably high
185temperatures, and in some cases the reported temperature declines if the actual
186temperature increases (similar to the raw PECI temperature value - see PECI
187specification for details). CPUTIN should therefore be be ignored on ASUS
188boards. The CPU temperature on ASUS boards is reported from PECI 0.