[Intel-gfx] Broken DPMS with DisplayPort on CHV (also BYT?)

Sridhara.Venkatanara at dell.com Sridhara.Venkatanara at dell.com
Fri Jan 27 07:13:56 UTC 2017

Please find My replay.



-----Original Message-----
From: Takashi Iwai [mailto:tiwai at suse.de]
Sent: Thursday, January 26, 2017 7:50 PM
To: Ville Syrjälä <ville.syrjala at linux.intel.com>
Cc: intel-gfx <intel-gfx at lists.freedesktop.org>; Michal Marek <mmarek at suse.cz>; Chen, Angus <angus.chen at intel.com>; Jeffrey Cheung <jcheung at suse.com>; Hsu, Ray <ray.hsu at intel.com>; Venkatanara, Sridhara <Sridhara_Venkatanara at DELL.com>
Subject: Re: [Intel-gfx] Broken DPMS with DisplayPort on CHV (also BYT?)

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?

[Sridhar] Monitor types  E2316H, E2216H


> > 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 :)

[Sridhar] It is tied to the Cherry Trail based box. Not observed with Bay Trail machines.

> > - 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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