Bug 193261

(creating a new bug, as suggested in https://bugzilla.kernel.org/show_bug.cgi?id=109051#c700)

After kernel update (and distribution change) from 4.4.0 (Ubuntu 16.04LTS) to 4.8.6 (Fedora 25) kernel is freezing randomly after 5 minutes up to several hours (10 at most) of uptime (most of the freezes occur up to 2hrs after reboot).
When a freeze occurs, the computer stops responding completely (mouse, keyboard input, ctrl-alt-Fx keys, not even "Magic RysRq" keys work), display remains intact and CPU fan runs totally up in few seconds after freeze - only hard reset/power off is the way out.

Hardware - notebook Toshiba Tecra R840-110 containing:
- Intel(R) Core(TM) i5-2520M CPU @ 2.50GHz (Sandy Bridge)
- Network controller: Intel Corporation Centrino Advanced-N 6230 [Rainbow Peak] (rev 34) (will be important, see below)

OS: Fedora 25, kernel 4.8.6-300.fc25.x86_64

Partial workaround:
- script c6off+c7on from Wolfgang Reimer found on another bug related to baytrail (https://bugzilla.kernel.org/show_bug.cgi?id=109051#c434) slightly updated to match state names in Sandy Bridge
- system is running and can be used without any problem for many hours (tested up to 8hrs, several months, every day)
- small drawback - system must not be left idle. If left idle (no sleep, simply on without being used), will freeze within 20-30 minutes (which is something I found out later) - this seems to be caused somehow by WIFI module, because after disabling Network Manager and removing WIFI kernel module (using rmmod), system has survived idle for more than 16 hrs

Update to the latest kernel 4.9.X (4.9.3, 4.9.4 for example) made things worser as the script from Wolfgang Reimer completely stopped working and the freezes are coming randomly again regardless if the computer is idle or not.
On the other hand, kernel version 4.4.0 (Ubuntu 16.04LTS) seems to work well (few small problems but no freezes).

For more details, please take a look on my original post (https://bugzilla.kernel.org/show_bug.cgi?id=109051#c699), or let me know if I can do something to help identifying the problem...

Thank You very much

(PS: memtest has been started and passed without errors)