17ebd8b66SMauro Carvalho ChehabKernel driver pwm-fan 27ebd8b66SMauro Carvalho Chehab===================== 37ebd8b66SMauro Carvalho Chehab 47ebd8b66SMauro Carvalho ChehabThis driver enables the use of a PWM module to drive a fan. It uses the 57ebd8b66SMauro Carvalho Chehabgeneric PWM interface thus it is hardware independent. It can be used on 67ebd8b66SMauro Carvalho Chehabmany SoCs, as long as the SoC supplies a PWM line driver that exposes 77ebd8b66SMauro Carvalho Chehabthe generic PWM API. 87ebd8b66SMauro Carvalho Chehab 97ebd8b66SMauro Carvalho ChehabAuthor: Kamil Debski <k.debski@samsung.com> 107ebd8b66SMauro Carvalho Chehab 117ebd8b66SMauro Carvalho ChehabDescription 127ebd8b66SMauro Carvalho Chehab----------- 137ebd8b66SMauro Carvalho Chehab 147ebd8b66SMauro Carvalho ChehabThe driver implements a simple interface for driving a fan connected to 157ebd8b66SMauro Carvalho Chehaba PWM output. It uses the generic PWM interface, thus it can be used with 167ebd8b66SMauro Carvalho Chehaba range of SoCs. The driver exposes the fan to the user space through 177ebd8b66SMauro Carvalho Chehabthe hwmon's sysfs interface. 187ebd8b66SMauro Carvalho Chehab 197ebd8b66SMauro Carvalho ChehabThe fan rotation speed returned via the optional 'fan1_input' is extrapolated 207ebd8b66SMauro Carvalho Chehabfrom the sampled interrupts from the tachometer signal within 1 second. 21*b99152d4SAlexander Stein 22*b99152d4SAlexander SteinThe driver provides the following sensor accesses in sysfs: 23*b99152d4SAlexander Stein 24*b99152d4SAlexander Stein=============== ======= ======================================================= 25*b99152d4SAlexander Steinfan1_input ro fan tachometer speed in RPM 26*b99152d4SAlexander Steinpwm1_enable rw keep enable mode, defines behaviour when pwm1=0 27*b99152d4SAlexander Stein 0 -> disable pwm and regulator 28*b99152d4SAlexander Stein 1 -> enable pwm; if pwm==0, disable pwm, keep regulator enabled 29*b99152d4SAlexander Stein 2 -> enable pwm; if pwm==0, keep pwm and regulator enabled 30*b99152d4SAlexander Stein 3 -> enable pwm; if pwm==0, disable pwm and regulator 31*b99152d4SAlexander Steinpwm1 rw relative speed (0-255), 255=max. speed. 32*b99152d4SAlexander Stein=============== ======= ======================================================= 33