1*7ebd8b66SMauro Carvalho ChehabKernel driver g760a 2*7ebd8b66SMauro Carvalho Chehab=================== 3*7ebd8b66SMauro Carvalho Chehab 4*7ebd8b66SMauro Carvalho ChehabSupported chips: 5*7ebd8b66SMauro Carvalho Chehab 6*7ebd8b66SMauro Carvalho Chehab * Global Mixed-mode Technology Inc. G760A 7*7ebd8b66SMauro Carvalho Chehab 8*7ebd8b66SMauro Carvalho Chehab Prefix: 'g760a' 9*7ebd8b66SMauro Carvalho Chehab 10*7ebd8b66SMauro Carvalho Chehab Datasheet: Publicly available at the GMT website 11*7ebd8b66SMauro Carvalho Chehab 12*7ebd8b66SMauro Carvalho Chehab http://www.gmt.com.tw/product/datasheet/EDS-760A.pdf 13*7ebd8b66SMauro Carvalho Chehab 14*7ebd8b66SMauro Carvalho ChehabAuthor: Herbert Valerio Riedel <hvr@gnu.org> 15*7ebd8b66SMauro Carvalho Chehab 16*7ebd8b66SMauro Carvalho ChehabDescription 17*7ebd8b66SMauro Carvalho Chehab----------- 18*7ebd8b66SMauro Carvalho Chehab 19*7ebd8b66SMauro Carvalho ChehabThe GMT G760A Fan Speed PWM Controller is connected directly to a fan 20*7ebd8b66SMauro Carvalho Chehaband performs closed-loop control of the fan speed. 21*7ebd8b66SMauro Carvalho Chehab 22*7ebd8b66SMauro Carvalho ChehabThe fan speed is programmed by setting the period via 'pwm1' of two 23*7ebd8b66SMauro Carvalho Chehabconsecutive speed pulses. The period is defined in terms of clock 24*7ebd8b66SMauro Carvalho Chehabcycle counts of an assumed 32kHz clock source. 25*7ebd8b66SMauro Carvalho Chehab 26*7ebd8b66SMauro Carvalho ChehabSetting a period of 0 stops the fan; setting the period to 255 sets 27*7ebd8b66SMauro Carvalho Chehabfan to maximum speed. 28*7ebd8b66SMauro Carvalho Chehab 29*7ebd8b66SMauro Carvalho ChehabThe measured fan rotation speed returned via 'fan1_input' is derived 30*7ebd8b66SMauro Carvalho Chehabfrom the measured speed pulse period by assuming again a 32kHz clock 31*7ebd8b66SMauro Carvalho Chehabsource and a 2 pulse-per-revolution fan. 32*7ebd8b66SMauro Carvalho Chehab 33*7ebd8b66SMauro Carvalho ChehabThe 'alarms' file provides access to the two alarm bits provided by 34*7ebd8b66SMauro Carvalho Chehabthe G760A chip's status register: Bit 0 is set when the actual fan 35*7ebd8b66SMauro Carvalho Chehabspeed differs more than 20% with respect to the programmed fan speed; 36*7ebd8b66SMauro Carvalho Chehabbit 1 is set when fan speed is below 1920 RPM. 37*7ebd8b66SMauro Carvalho Chehab 38*7ebd8b66SMauro Carvalho ChehabThe g760a driver will not update its values more frequently than every 39*7ebd8b66SMauro Carvalho Chehabother second; reading them more often will do no harm, but will return 40*7ebd8b66SMauro Carvalho Chehab'old' values. 41