17ebd8b66SMauro Carvalho ChehabKernel driver g760a 27ebd8b66SMauro Carvalho Chehab=================== 37ebd8b66SMauro Carvalho Chehab 47ebd8b66SMauro Carvalho ChehabSupported chips: 57ebd8b66SMauro Carvalho Chehab 67ebd8b66SMauro Carvalho Chehab * Global Mixed-mode Technology Inc. G760A 77ebd8b66SMauro Carvalho Chehab 87ebd8b66SMauro Carvalho Chehab Prefix: 'g760a' 97ebd8b66SMauro Carvalho Chehab 107ebd8b66SMauro Carvalho Chehab Datasheet: Publicly available at the GMT website 117ebd8b66SMauro Carvalho Chehab 127ebd8b66SMauro Carvalho Chehab http://www.gmt.com.tw/product/datasheet/EDS-760A.pdf 137ebd8b66SMauro Carvalho Chehab 147ebd8b66SMauro Carvalho ChehabAuthor: Herbert Valerio Riedel <hvr@gnu.org> 157ebd8b66SMauro Carvalho Chehab 167ebd8b66SMauro Carvalho ChehabDescription 177ebd8b66SMauro Carvalho Chehab----------- 187ebd8b66SMauro Carvalho Chehab 197ebd8b66SMauro Carvalho ChehabThe GMT G760A Fan Speed PWM Controller is connected directly to a fan 207ebd8b66SMauro Carvalho Chehaband performs closed-loop control of the fan speed. 217ebd8b66SMauro Carvalho Chehab 227ebd8b66SMauro Carvalho ChehabThe fan speed is programmed by setting the period via 'pwm1' of two 237ebd8b66SMauro Carvalho Chehabconsecutive speed pulses. The period is defined in terms of clock 247ebd8b66SMauro Carvalho Chehabcycle counts of an assumed 32kHz clock source. 257ebd8b66SMauro Carvalho Chehab 267ebd8b66SMauro Carvalho ChehabSetting a period of 0 stops the fan; setting the period to 255 sets 277ebd8b66SMauro Carvalho Chehabfan to maximum speed. 287ebd8b66SMauro Carvalho Chehab 297ebd8b66SMauro Carvalho ChehabThe measured fan rotation speed returned via 'fan1_input' is derived 307ebd8b66SMauro Carvalho Chehabfrom the measured speed pulse period by assuming again a 32kHz clock 317ebd8b66SMauro Carvalho Chehabsource and a 2 pulse-per-revolution fan. 327ebd8b66SMauro Carvalho Chehab 337ebd8b66SMauro Carvalho ChehabThe 'alarms' file provides access to the two alarm bits provided by 347ebd8b66SMauro Carvalho Chehabthe G760A chip's status register: Bit 0 is set when the actual fan 357ebd8b66SMauro Carvalho Chehabspeed differs more than 20% with respect to the programmed fan speed; 367ebd8b66SMauro Carvalho Chehabbit 1 is set when fan speed is below 1920 RPM. 377ebd8b66SMauro Carvalho Chehab 387ebd8b66SMauro Carvalho ChehabThe g760a driver will not update its values more frequently than every 397ebd8b66SMauro Carvalho Chehabother second; reading them more often will do no harm, but will return 407ebd8b66SMauro Carvalho Chehab'old' values. 41