[Bug 101059] New: [GLK] Blank screen with Acer S277HK monitor at 12bpc 2560x1440 at 60

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=101059

            Bug ID: 101059
           Summary: [GLK] Blank screen with Acer S277HK monitor at 12bpc
                    2560x1440 at 60
           Product: DRI
           Version: DRI git
          Hardware: Other
                OS: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: DRM/Intel
          Assignee: intel-gfx-bugs at lists.freedesktop.org
          Reporter: conselvan2 at gmail.com
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

This was initially discussed in bug #100440, which tracked a different issue.

Attempting to enable the 2560x1440 mode with 12 bpc in an Acer S277HK monitor
leads to a blank screen.


from bug 100440, comment 19
> I also tested enabling the given mode with only scrambling and only high
> tmds. 
> 
> scrambling	high tmds	result
> yes		yes		fail
> yes		no		pass	
> no		yes		fail
> no		no		pass
> 
> So this seems to be a combination of 12 bpc, a port clock in the range
> [340,405) and high tmds ratios. But as far as I can tell, we are following
> the spec with respect to those. Shashank, any ideas?


from bug 100440, commend 32
> I was able to get this issue tested with a HDMI analyzer too. 
> Here are the updates:
...
> - The display never fails when using the analyzer. It only fails using real
> monitor. 
> - Scrambling and clock high ratio is getting enabled/set/disabled properly. 
> - Bootup and modeset dmesg logs attached.
> 
> I think this is a fault with monitor, which is not able to handle this mode
> at 12BPC (Also, This mode is a non-CEA modes, so not a standard one too)

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