Bug 101059

Summary:	[GLK] Blank screen with Acer S277HK monitor at 12bpc 2560x1440@60
Product:	DRI	Reporter:	Ander Conselvan de Oliveira <conselvan2>
Component:	DRM/Intel	Assignee:	Ander Conselvan de Oliveira <conselvan2>
Status:	CLOSED INVALID	QA Contact:	Intel GFX Bugs mailing list <intel-gfx-bugs>
Severity:	normal
Priority:	medium	CC:	conselvan2, intel-gfx-bugs, luis.botello.ortega, shashank.sharma
Version:	DRI git
Hardware:	Other
OS:	All
Whiteboard:
i915 platform:	GLK	i915 features:	display/HDMI

Description Ander Conselvan de Oliveira 2017-05-16 13:11:01 UTC

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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