On Monday 30 May 2016 13:45:51 Thorsten Leemhuis wrote: > Pali Rohár wrote on 27.05.2016 15:21: > > On Friday 27 May 2016 15:05:54 Thorsten Leemhuis wrote: > >> Pali Rohár wrote on 27.05.2016 12:45: > >> So I tried a few things > >> and came to the conclusion: the problem shows up as soon as > >> i8k_get_fan_type() (introduced in f989e55452) is called somewhere. > > > > So, once kernel call i8k_get_fan_type() function, then fan speed > > going up/down? > > Yes. > > > To make sure that this is root of your problem, can you take some > > older kernel version (where is i8k working fine) and try to > > patch+call that i8k_get_fan_type() function? To check that > > something else cannot interference with it... > > I just tried with 3.19.8 (had to install a older distro first :-/ ), > where the problem does not show up (I verified just to be sure). Then > I applied below patch and voila: the fan speed starts going up/down. > > IOW: From what I can see that SMM call that i8k_get_fan_type() > triggers the problem on my Studio 8000 > > CU, knurd > Thank you for your testing! I believe now we definitely know root of this problem. It is buggy Dell BIOS/SMM code and we need to avoid calling I8K_SMM_GET_FAN_TYPE on affected buggy Dell machines. -- Pali Rohár pali.rohar@xxxxxxxxx
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