hwmon: (nct6775) Add support for automatic fan control

Signed-off-by: Guenter Roeck <linux@roeck-us.net>

1 files changed, 69 insertions, 0 deletions

diff --git a/Documentation/hwmon/nct6775 b/Documentation/hwmon/nct6775
index 7c9f1d303913..b4fe6bc4d371 100644
--- a/Documentation/hwmon/nct6775
+++ b/Documentation/hwmon/nct6775
@@ -87,6 +87,75 @@ pwm[1-5]_mode - controls if output is PWM or DC level
         * 0 DC output
         * 1 PWM output
 
+Common fan control attributes
+-----------------------------
+
+pwm[1-5]_temp_sel       Temperature source. Value is temperature sensor index.
+                        For example, select '1' for temp1_input.
+
+Thermal Cruise mode (2)
+-----------------------
+
+If the temperature is in the range defined by:
+
+pwm[1-5]_target_temp    Target temperature, unit millidegree Celsius
+                        (range 0 - 127000)
+pwm[1-5]_temp_tolerance
+                        Target temperature tolerance, unit millidegree Celsius
+
+there are no changes to fan speed. Once the temperature leaves the interval, fan
+speed increases (if temperature is higher that desired) or decreases (if
+temperature is lower than desired), using the following limits and time
+intervals.
+
+pwm[1-5]_start          fan pwm start value (range 1 - 255), to start fan
+                        when the temperature is above defined range.
+pwm[1-5]_floor          lowest fan pwm (range 0 - 255) if temperature is below
+                        the defined range. If set to 0, the fan is expected to
+                        stop if the temperature is below the defined range.
+pwm[1-5]_step_up_time   milliseconds before fan speed is increased
+pwm[1-5]_step_down_time milliseconds before fan speed is decreased
+pwm[1-5]_stop_time      how many milliseconds must elapse to switch
+                        corresponding fan off (when the temperature was below
+                        defined range).
+
+Speed Cruise mode (3)
+---------------------
+
+This modes tries to keep the fan speed constant.
+
+fan[1-5]_target         Target fan speed
+fan[1-5]_tolerance
+                        Target speed tolerance
+
+
+Untested; use at your own risk.
+
+Smart Fan IV mode (5)
+---------------------
+
+This mode offers multiple slopes to control the fan speed. The slopes can be
+controlled by setting the pwm and temperature attributes. When the temperature
+rises, the chip will calculate the DC/PWM output based on the current slope.
+There are up to seven data points depending on the chip type. Subsequent data
+points should be set to higher temperatures and higher pwm values to achieve
+higher fan speeds with increasing temperature. The last data point reflects
+critical temperature mode, in which the fans should run at full speed.
+
+pwm[1-5]_auto_point[1-7]_pwm
+                        pwm value to be set if temperature reaches matching
+                        temperature range.
+pwm[1-5]_auto_point[1-7]_temp
+                        Temperature over which the matching pwm is enabled.
+pwm[1-5]_temp_tolerance
+                        Temperature tolerance, unit millidegree Celsius
+pwm[1-5]_crit_temp_tolerance
+                        Temperature tolerance for critical temperature,
+                        unit millidegree Celsius
+
+pwm[1-5]_step_up_time   milliseconds before fan speed is increased
+pwm[1-5]_step_down_time milliseconds before fan speed is decreased
+
 Usage Notes
 -----------