i915: occasional hangs on Baytrail with deeper C-states

Daniel Bilik ddb at neosystem.org
Sun May 15 13:17:08 PDT 2016

I was probably too verbose in my previous post, making it unclear...

On Fri, 13 May 2016 08:56:53 +0200
Francois Tigeot <ftigeot at wolfpond.org> wrote:

> The problem is, both commits are present in Linux 4.3 and the DragonFly 
> code in master:
> ...

Exactly, these commits are already in Linux and Dragonfly, and this is the
problem, because AFAICT they introduced instability of i915 driver on
Baytrail systems. And patches I've attached to my previous post seem to
stabilize it, at least on my system.

One of the patches (dfly-i915-vlv-avoid-aggressive-downclocking.diff) was
already comitted to Dragonfly as 5d8e0f4+, but has been "overwritten"
recently with commit a05eeeb+. The other one is just a "oneliner" to fix
another problematic code that is known to cause machine hangs.

Though the patches seem to work for me (ie. I'm able to run my system with
machdep.mwait.CX.idle=AUTODEEP), it would be great to get it confirmed also
by other user(s) that run Dragonfly on Baytrail.


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