Documentation/hwmon/nct6775

   1 Note
   2 ====
   3
   4 This driver supersedes the NCT6775F and NCT6776F support in the W83627EHF
   5 driver.
   6
   7 Kernel driver NCT6775
   8 =====================
   9
  10 Supported 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
  40 Authors:
  41         Guenter Roeck <linux@roeck-us.net>
  42
  43 Description
  44 -----------
  45
  46 This driver implements support for the Nuvoton NCT6775F, NCT6776F, and NCT6779D
  47 and compatible super I/O chips.
  48
  49 The chips support up to 25 temperature monitoring sources. Up to 6 of those are
  50 direct temperature sensor inputs, the others are special sources such as PECI,
  51 PCH, and SMBUS. Depending on the chip type, 2 to 6 of the temperature sources
  52 can be monitored and compared against minimum, maximum, and critical
  53 temperatures. The driver reports up to 10 of the temperatures to the user.
  54 There are 4 to 5 fan rotation speed sensors, 8 to 15 analog voltage sensors,
  55 one VID, alarms with beep warnings (control unimplemented), and some automatic
  56 fan regulation strategies (plus manual fan control mode).
  57
  58 The temperature sensor sources on all chips are configurable. The configured
  59 source for each of the temperature sensors is provided in tempX_label.
  60
  61 Temperatures are measured in degrees Celsius and measurement resolution is
  62 either 1 degC or 0.5 degC, depending on the temperature source and
  63 configuration. An alarm is triggered when the temperature gets higher than
  64 the high limit; it stays on until the temperature falls below the hysteresis
  65 value. Alarms are only supported for temp1 to temp6, depending on the chip type.
  66
  67 Fan rotation speeds are reported in RPM (rotations per minute). An alarm is
  68 triggered if the rotation speed has dropped below a programmable limit. On
  69 NCT6775F, fan readings can be divided by a programmable divider (1, 2, 4, 8,
  70 16, 32, 64 or 128) to give the readings more range or accuracy; the other chips
  71 do not have a fan speed divider. The driver sets the most suitable fan divisor
  72 itself; specifically, it increases the divider value each time a fan speed
  73 reading returns an invalid value, and it reduces it if the fan speed reading
  74 is lower than optimal. Some fans might not be present because they share pins
  75 with other functions.
  76
  77 Voltage sensors (also known as IN sensors) report their values in millivolts.
  78 An alarm is triggered if the voltage has crossed a programmable minimum
  79 or maximum limit.
  80
  81 The driver supports automatic fan control mode known as Thermal Cruise.
  82 In this mode, the chip attempts to keep the measured temperature in a
  83 predefined temperature range. If the temperature goes out of range, fan
  84 is driven slower/faster to reach the predefined range again.
  85
  86 The mode works for fan1-fan5.
  87
  88 sysfs attributes
  89 ----------------
  90
  91 pwm[1-5] - this file stores PWM duty cycle or DC value (fan speed) in range:
  92            0 (lowest speed) to 255 (full)
  93
  94 pwm[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
 102 pwm[1-5]_mode - controls if output is PWM or DC level
 103         * 0 DC output
 104         * 1 PWM output
 105
 106 Common fan control attributes
 107 -----------------------------
 108
 109 pwm[1-5]_temp_sel       Temperature source. Value is temperature sensor index.
 110                         For example, select '1' for temp1_input.
 111 pwm[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
 116 If secondary temperature functionality is enabled, it is controlled with the
 117 following attributes.
 118
 119 pwm[1-5]_weight_duty_step
 120                         Duty step size.
 121 pwm[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.
 125 pwm[1-5]_weight_temp_step_base
 126                         Temperature at which secondary temperature control kicks
 127                         in.
 128 pwm[1-5]_weight_temp_step_tol
 129                         Temperature step tolerance.
 130
 131 Thermal Cruise mode (2)
 132 -----------------------
 133
 134 If the temperature is in the range defined by:
 135
 136 pwm[1-5]_target_temp    Target temperature, unit millidegree Celsius
 137                         (range 0 - 127000)
 138 pwm[1-5]_temp_tolerance
 139                         Target temperature tolerance, unit millidegree Celsius
 140
 141 there are no changes to fan speed. Once the temperature leaves the interval, fan
 142 speed increases (if temperature is higher that desired) or decreases (if
 143 temperature is lower than desired), using the following limits and time
 144 intervals.
 145
 146 pwm[1-5]_start          fan pwm start value (range 1 - 255), to start fan
 147                         when the temperature is above defined range.
 148 pwm[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.
 151 pwm[1-5]_step_up_time   milliseconds before fan speed is increased
 152 pwm[1-5]_step_down_time milliseconds before fan speed is decreased
 153 pwm[1-5]_stop_time      how many milliseconds must elapse to switch
 154                         corresponding fan off (when the temperature was below
 155                         defined range).
 156
 157 Speed Cruise mode (3)
 158 ---------------------
 159
 160 This modes tries to keep the fan speed constant.
 161
 162 fan[1-5]_target         Target fan speed
 163 fan[1-5]_tolerance
 164                         Target speed tolerance
 165
 166
 167 Untested; use at your own risk.
 168
 169 Smart Fan IV mode (5)
 170 ---------------------
 171
 172 This mode offers multiple slopes to control the fan speed. The slopes can be
 173 controlled by setting the pwm and temperature attributes. When the temperature
 174 rises, the chip will calculate the DC/PWM output based on the current slope.
 175 There are up to seven data points depending on the chip type. Subsequent data
 176 points should be set to higher temperatures and higher pwm values to achieve
 177 higher fan speeds with increasing temperature. The last data point reflects
 178 critical temperature mode, in which the fans should run at full speed.
 179
 180 pwm[1-5]_auto_point[1-7]_pwm
 181                         pwm value to be set if temperature reaches matching
 182                         temperature range.
 183 pwm[1-5]_auto_point[1-7]_temp
 184                         Temperature over which the matching pwm is enabled.
 185 pwm[1-5]_temp_tolerance
 186                         Temperature tolerance, unit millidegree Celsius
 187 pwm[1-5]_crit_temp_tolerance
 188                         Temperature tolerance for critical temperature,
 189                         unit millidegree Celsius
 190
 191 pwm[1-5]_step_up_time   milliseconds before fan speed is increased
 192 pwm[1-5]_step_down_time milliseconds before fan speed is decreased
 193
 194 Usage Notes
 195 -----------
 196
 197 On various ASUS boards with NCT6776F, it appears that CPUTIN is not really
 198 connected to anything and floats, or that it is connected to some non-standard
 199 temperature measurement device. As a result, the temperature reported on CPUTIN
 200 will not reflect a usable value. It often reports unreasonably high
 201 temperatures, and in some cases the reported temperature declines if the actual
 202 temperature increases (similar to the raw PECI temperature value - see PECI
 203 specification for details). CPUTIN should therefore be be ignored on ASUS
 204 boards. The CPU temperature on ASUS boards is reported from PECI 0.