[GTALUG] Intel Baytrail systems may become stable under Linux!

[D. Hugh Redelmeier]

For two years, Intel Baytrail processors have been hanging under
Linux.

Baytrail is a generation of Atom processors and includes many low-end
processors that I think of as Atoms but are called things like
Pentium and Celeron.  But not all Pentium and Celeron processors.
  <http://ark.intel.com/products/codename/55844/Bay-Trail>

The bug report is
  <https://bugzilla.kernel.org/show_bug.cgi?id=109051>
but started elsewhere.  A few days ago, entry 724 (!) in that bug
report noted the submission of a kernel patch that strongly reduces
the problem.  The thread for the patch is interesting:
  <https://lists.freedesktop.org/archives/intel-gfx/2017-January/117932.html>

- the fix doesn't fix all the underlying problems but very
  significantly improves stability.  Perhaps to the point that
  the instability fades into the background noise of crashes.

- the fix slightly cripples power management on these systems but much
  less than the only known work-around (preventing the use of cstates
  higher than 1)

- this may slow down the search for residual bugs, but how can it be
  slower than the current process has been?

- The fix was already in the kernel for Cherryview processors.  I'm
  not sure what those are: it certainly includes Cherry Trail processors.
	<http://ark.intel.com/products/codename/46629/Cherry-Trail>

- the bug started to become visible in Linux 3.17-rc1 and should be
  ameliorated in 4.11.  What a long horrible run.  Most of the life of
  the chips!

I have a number of Atom systems that I never got around to Linuxifying
due to fear of this bug and, for some, annoyance with 32-bit UEFI
firmware.  I will say that I've had a great experience with a netbook
with a Celeron N2840 (Baytrail).  Perhaps because I don't often play
video content with it.

Some of these Baytrail systems are still a nightmare for Linux due to 
non-systematic and undocumented connection of the SoCs to the peripheral 
circuits.  Here's a sample thread for one such system (more than 200 
entries!):
  <https://bugzilla.kernel.org/show_bug.cgi?id=95681>