hwmon/it87: Add PWM base frequency control
Let the user select the base PWM frequency when using the it87
hardware monitoring driver. Different frequencies can give better
control on some fans.
Also update the documentation to mention the PWM frequency control
files, with misc cleanups to the PWM section.
Signed-off-by: Jean Delvare <khali@linux-fr.org>
diff --git a/Documentation/hwmon/it87 b/Documentation/hwmon/it87
index 74a8099..c0528d6 100644
--- a/Documentation/hwmon/it87
+++ b/Documentation/hwmon/it87
@@ -135,6 +135,16 @@
startup, consult lm_sensors's /etc/sensors.conf. (2 = thermistor;
3 = thermal diode)
+
+Fan speed control
+-----------------
+
The fan speed control features are limited to manual PWM mode. Automatic
"Smart Guardian" mode control handling is not implemented. However
if you want to go for "manual mode" just write 1 to pwmN_enable.
+
+If you are only able to control the fan speed with very small PWM values,
+try lowering the PWM base frequency (pwm1_freq). Depending on the fan,
+it may give you a somewhat greater control range. The same frequency is
+used to drive all fan outputs, which is why pwm2_freq and pwm3_freq are
+read-only.