Messages in this thread | | | Date | Sat, 17 May 2014 15:18:54 -0700 | From | Guenter Roeck <> | Subject | Re: Dell Latitude E6440 & i8k |
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On 05/17/2014 02:09 PM, Jean Delvare wrote: > On Sat, 17 May 2014 08:25:38 -0700, Guenter Roeck wrote: >> On 05/16/2014 12:11 PM, Jean Delvare wrote: >>> Load the i8k driver with fan_mult=1. >> >> Would it make sense to change the default multiplier to 1 ? >> Lots of people have problems with it, and trying to figure out >> affected machines one by one would be an all but impossible task. > > That would cause a regression on many (presumably older) machines. I > doubt this is acceptable. One option would be to use the ACPI year to > change the default, if indeed all new machines need fan_mult=1. I don't > know if this is the case. > > One this I had in mind was auto-detecting the scaling factor. AFAIK > only 30 and 1 are possible values, so any value above ~300 would imply > scaling factor of 1 (30 would make it > 9000 RPM which is unrealistic.) > But I don't know if we can actually do that, as such a simple heuristic > could easily fail is the fan is stopped (30 * 0 == 1 * 0) or if the > returned raw speed is temporarily unreliable for whatever reason. > Sounds like an idea. We could make the cutoff higher, such as 500 or even 1000. I am not much concerned about 0 rpm - the code could simply check the returned rpm and adjust the scaling factor to 1 if the reading is too high. Since 30*0 is still 0, there is no problem if the fan is stopped.
> I have to admit that working on a reverse engineered driver for > hardware I don't even have isn't quite at the top of my to-do list. >
;-). We have several of those systems, so there is at least some interest on my side. If I have time, I'll play around with it. The driver does need major cleanup, though, so that may take a while.
Guenter
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