[Bug 102820] [bisected][DC] commit ebbf7337e2daacacef3e01114e6be68a2a4f11b4 prevents X11 from starting

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=102820

--- Comment #13 from Alex Deucher <alexdeucher at gmail.com> ---
(In reply to dwagner from comment #11)
> 
> This is the manufacturers page advertising my graphics board:
> 
> http://www.xfxforce.com/en-us/products/amd-radeon-rx-400-series/rx-460-4gb-
> heatsink-rx-460p4hfg5-
> 
> It couldn't be more affirmative regarding support of HDMI 2.0b and high
> refresh rates for 4k modes...

It's pretty vague unfortunately regarding HDMI:

"Latest Display Connections

Ready for the latest displays

Radeon™ GPUs with the Polaris architecture support HDMI® 2.0b and DisplayPort™
1.3 for compatibility with a new generation of monitors that would make any
gamer excited:

• 1080p @ 240Hz • 1440p @ 240Hz • 4K @ 120Hz • 1440p ultra-wide @ 190Hz"

It does not explicitly say 4K at 60 on HDMI.  The high refresh rates may only be
available on DP.  HDMI 2.0b does not imply 4K at 60.

> 
> (And practical experience during the last months also tells me: Yes, HDMI 4k
> @ 60Hz output is stable - even when using a 4m length HDMI cable.
> 

Your board may work, but others might not depending on the board, cable,
monitor, etc.

> > The driver drops the higher bandwidth modes for HDMI connectors if the board
> > does not support them.
> 
> I have looked if there are any firmware upgrades for this card or any hints
> from others regarding lack of 4k 60 Hz support, but found neither. (I only
> found unofficial firmware that switches on shader units the manufacturer
> keeps dormant, but I am not using that.)

The display features that are validated are stored in the vbios and the vbios
is updated by the board vendor based on what features they validated on the
board.

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