linux/Documentation/hwmon/g760a
Herbert Valerio Riedel 3bcfa9e47a hwmon: add support for GMT G760A fan speed PWM controller
This controller can be found on the D-Link DNS-323 for instance, where
it is to be configured via static i2c_board_info in the board-specific
mach-orion/dns323-setup.c; this driver supports only the new-style
driver model.

Tested-by: Martin Michlmayr <tbm@cyrius.com>
Signed-off-by: Herbert Valerio Riedel <hvr@gnu.org>
Signed-off-by: Matthew Palmer <mpalmer@debian.org>
Signed-off-by: Laurie Bradshaw <bradshaw.laurie@googlemail.com>
Signed-off-by: Martin Michlmayr <tbm@cyrius.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-04-07 08:31:03 -07:00

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Kernel driver g760a
===================
Supported chips:
* Global Mixed-mode Technology Inc. G760A
Prefix: 'g760a'
Datasheet: Publicly available at the GMT website
http://www.gmt.com.tw/datasheet/g760a.pdf
Author: Herbert Valerio Riedel <hvr@gnu.org>
Description
-----------
The GMT G760A Fan Speed PWM Controller is connected directly to a fan
and performs closed-loop control of the fan speed.
The fan speed is programmed by setting the period via 'pwm1' of two
consecutive speed pulses. The period is defined in terms of clock
cycle counts of an assumed 32kHz clock source.
Setting a period of 0 stops the fan; setting the period to 255 sets
fan to maximum speed.
The measured fan rotation speed returned via 'fan1_input' is derived
from the measured speed pulse period by assuming again a 32kHz clock
source and a 2 pulse-per-revolution fan.
The 'alarms' file provides access to the two alarm bits provided by
the G760A chip's status register: Bit 0 is set when the actual fan
speed differs more than 20% with respect to the programmed fan speed;
bit 1 is set when fan speed is below 1920 RPM.
The g760a driver will not update its values more frequently than every
other second; reading them more often will do no harm, but will return
'old' values.