From 3bcfa9e47a7d1be6faef3be6c4b2049e585e2f38 Mon Sep 17 00:00:00 2001 From: Herbert Valerio Riedel Date: Mon, 6 Apr 2009 19:00:30 -0700 Subject: 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 Signed-off-by: Herbert Valerio Riedel Signed-off-by: Matthew Palmer Signed-off-by: Laurie Bradshaw Signed-off-by: Martin Michlmayr Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/hwmon/g760a | 36 ++++++++++++++++++++++++++++++++++++ 1 file changed, 36 insertions(+) create mode 100644 Documentation/hwmon/g760a (limited to 'Documentation/hwmon') diff --git a/Documentation/hwmon/g760a b/Documentation/hwmon/g760a new file mode 100644 index 00000000000..e032eeb7562 --- /dev/null +++ b/Documentation/hwmon/g760a @@ -0,0 +1,36 @@ +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 + +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. -- cgit v1.2.3-70-g09d2