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Thanks Sridhar -----Original Message----- From: Takashi Iwai [mailto:ti...@suse.de] Sent: Thursday, January 26, 2017 7:50 PM To: Ville Syrjälä <ville.syrj...@linux.intel.com> Cc: intel-gfx <intel-gfx@lists.freedesktop.org>; Michal Marek <mma...@suse.cz>; Chen, Angus <angus.c...@intel.com>; Jeffrey Cheung <jche...@suse.com>; Hsu, Ray <ray....@intel.com>; Venkatanara, Sridhara <sridhara_venkatan...@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 http://www.dell.com/ed/business/p/dell-e2316h-monitor/pd > > 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. Thanks! Takashi
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