[lm-sensors] Looking for IT8720 datasheet.
fmyhr at fhmtech.com
Fri Oct 3 19:14:31 CEST 2008
Jean-Marc Spaggiari wrote:
>>> Regarding pwm4 and pwm5, I'm not really sure how to do
>> Simplest and probably best to just ignore/don't worry about pwm4 and
>> pwm5 for now. Letting the user select pwm4 and pwm5 control will require
>> new sysfs attributes, there is currently no standard for these.
>> Something like:
>> which could take values [1|2|3]
>> But I haven't yet successfully used pwm control on fans 4 and 5 on my
>> boards, not yet sure it's possible, so it's probably premature to
>> consider new sysfs interfaces for potentially useless features.
To clear up some confusion (please see file sysfs-interface):
fan1_input thru fan5_input are measured fan rpms
pwm1 thru pwm5 are driving fan voltage pulse-width-modulation duty
cycles in range 0-255. (Some boards convert pwm to linearized dc voltage).
> When I force has_fan to 5 fans, I get:
> fan1: 3000 RPM (min = 0 RPM)
> fan2: 0 RPM (min = 0 RPM)
> fan3: 5973 RPM (min = 0 RPM)
> fan4: -1 RPM (min = -1 RPM)
> fan5: -1 RPM (min = -1 RPM)
> So can I just help him to read to pwm 4 and 5 correctly?
The -1 values you're reporting for fan4 and fan5 come from
#define FAN16_FROM_REG(val) ((val)==0?-1:(val)==0xffff?0:1350000/((val)*2))
In other words, the 8720 reports "0", the above macro converts that to
-1. (I'm not entirely clear why this is done.)
> Regarding the resistors. should I publish the values? Or it's useless?
I think it would help at least other users of your board. Perhaps add it
to Documentation/hwmon/it87 ?
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