[Intel-gfx] Broken DPMS with DisplayPort on CHV (also BYT?)
tiwai at suse.de
Thu Jan 26 14:19:44 UTC 2017
On Thu, 26 Jan 2017 14:58:55 +0100,
Ville Syrjälä wrote:
> On Wed, Jan 25, 2017 at 01:56:35PM +0100, Takashi Iwai wrote:
> > Hi,
> > we've got a bug report about the blank monitor on Cherry Trail
> > machines. And, Intel team (Cc'ed) spotted out that this seems
> > triggered by DPMS transition. A patch like below actually fixes the
> > problem.
> > Of course it doesn't look like a right "fix". Do you guys have any
> > hint for further debugging?
> Is it some kind of new fangled MST capable monitor? I've noticed that
> those tend to be super easy to mess up.
The monitors are in Dell team. Sridhara, could you give details about
the problematic monitors?
> > Some more (not alt-) facts:
> > - The machine we've tested is a Cherry Trail based box with two
> > DisplayPorts. Intel team mentioned that there are other machines
> > suffering from the same problem.
> Is it really somehow tied to the machine? I would imagine it should
> behave exactly the same way no matter what machine you have.
A good question. Again the question is delegated to Sridhara :)
> > - With some monitors, the screen remains blank during boot and on X.
> > This can be cured after "xset dpms force off" and resume, or
> > reconfiguring via xrandr.
> > - The issue seems specific to DP connections. When two (identical)
> > monitors are connected, only one monitor goes blank.
> Hmm. Have you tried 9f2bdb006a7e ("drm/i915: Prevent PPS stealing
> from a normal DP port on VLV/CHV") ?
No, it's not tested. I'll prepare a test kernel with it.
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