Bug#919115: linux-image-4.19.0-0.bpo.1-amd64-unsigned: Graphical glitches (lightdm and cinnamon) after upgrading linux (RadeonRX540)

[N G <ledufff@hotmail.com>]

Few things about using 'amdgpu.dc=0' as a workaround for graphical 
glitches.

I can't get any HDMI audio output (works correctly with the default 
parameters).

On the other hand, redshift doesn't seem to be working correctly with 
'amdgpu.dc=0' (cursor temperature remains at 6500K). This works 
correctly as well with the default parameters.

> A workaround for this bug it's using 'amdgpu.dc=0'.  No more glitches
> for wallpapers, screensaver, or lightdm.
>