[Bug 101373] [KBL] modeset to a different refresh rate periodically results in a black screen

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=101373

--- Comment #15 from Joseph Yasi <joe.yasi at gmail.com> ---
Denon suggested a possible signaling issue at first. They suggested trying
shorter cables, and using a the HDMI input port closest to the output on the
receiver. I was already doing that, and I switched out a 10 ft cable for a 6 ft
cable, and used cables rated for HDMI 2.0 bandwidth with no change.

I noticed in the dmesg that the driver is setting a 12 bpc mode:
[  310.091302] [drm:intel_hdmi_compute_config [i915]] picking bpc to 12 for
HDMI output
[  310.091333] [drm:intel_hdmi_compute_config [i915]] forcing pipe bpc to 36
for HDMI
[  310.091366] [drm:intel_atomic_check [i915]] hw max bpp: 36, pipe bpp: 36,
dithering: 0

Denon suggested forcing a 10 bpc mode to see if it helps the issue. I noticed
the problem is worse if I set a 3840x2160 @ 30 Hz mode and then toggle back to
1080p @ 60 Hz and 1080p @ 59.94 Hz. I'm only using 8 bpc in the X
configuration. Is there a way for me to force 10 or 8 bpc on the physical mode?

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