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>

1 files changed, 10 insertions, 5 deletions

diff --git a/Documentation/hwmon/sysfs-interface b/Documentation/hwmon/sysfs-interface
index efef3b962cd3..d73d2e8c7534 100644
--- a/Documentation/hwmon/sysfs-interface
+++ b/Documentation/hwmon/sysfs-interface
@@ -166,16 +166,21 @@ pwm[1-*]	Pulse width modulation fan control.
 
 pwm[1-*]_enable
                 Switch PWM on and off.
-                Not always present even if fan*_pwm is.
+                Not always present even if pwmN is.
                 0: turn off
                 1: turn on in manual mode
                 2+: turn on in automatic mode
-                Check individual chip documentation files for automatic mode details.
+                Check individual chip documentation files for automatic mode
+                details.
                 RW
 
-pwm[1-*]_mode
-                0: DC mode
-                1: PWM mode
+pwm[1-*]_mode   0: DC mode (direct current)
+                1: PWM mode (pulse-width modulation)
+                RW
+
+pwm[1-*]_freq   Base PWM frequency in Hz.
+                Only possibly available when pwmN_mode is PWM, but not always
+                present even then.
                 RW
 
 pwm[1-*]_auto_channels_temp