External Monitor Output broken with Kernel 5.10 (Regression)
With Kernel 5.10 my external Monitor, (connected to a Laptop via HDMI output -> DVI converter -> DVI Input on the Display, is broken. The output is blue and blurry. The output is already broken in boot, before X even starts. It worked fine with Kernel 5.9.
Model name: Intel(R) Core(TM) i7-10610U CPU @ 1.80GHz
Manufacturer: Dell Inc.
Product Name: Latitude 7410
But I did a bisect:
181567aa9f0d297804f1ea5d3ff4ba4518e05f2c is the first bad commit commit 181567aa9f0d297804f1ea5d3ff4ba4518e05f2c Author: Ville Syrjälä <email@example.com> Date: Fri Sep 4 14:53:54 2020 +0300 drm/i915: Do YCbCr 444->420 conversion via DP protocol converters For platforms that can't do native 4:2:0 outout we may still be able to do it by getting the DP->HDMI protocol converter to perform the 4:4:4->4:2:0 downsamling for us. In this case we have to configure our hardware to output YCbCr 4:4:4, which we've already hooked up so all we need to do is flip the switch. Signed-off-by: Ville Syrjälä <firstname.lastname@example.org> Link: https://email@example.com Reviewed-by: Lyude Paul <firstname.lastname@example.org> Acked-by: Daniel Vetter <email@example.com> drivers/gpu/drm/i915/display/intel_display_types.h | 1 + drivers/gpu/drm/i915/display/intel_dp.c | 121 +++++++++++++++++---- drivers/gpu/drm/i915/display/intel_hdmi.c | 8 +- drivers/gpu/drm/i915/display/intel_hdmi.h | 4 +- 4 files changed, 109 insertions(+), 25 deletions(-)
NOTE: To recover from this issue a simple reboot to kernel 5.9 is not enough. I MUST turn off the laptop and wait a few seconds, otherwise the issue remains with kernel 5.9.