While trying to fix another bug I tried using kernel v4.0 and noticed that
after X.org has started (running fluxbox with mythtv in my case) the screen
stays black. My screen is attached on HDMI.
During boot I can see the console output just fine but when X started it stays
black. I don't even see the first small X shaped cursor.
I bisected this back to commit 0ea5fe8a83c2 ("drm/nouveau/kms: default to panel
scaling, except for fixed panels prior to nv50").
>From the commit message I suspect that "panel scaling" (whatever that means)
does not work on my NVAA. I check the values of nv_connector->type and
nv_connector->scaling_mode on both the bisected commit and the parent (last
commit working).
The type is 0x61 (DCB_CONNECTOR_HDMI_1) in both cases and the scaling_mode is 0
(DRM_MODE_SCALE_NONE) when the screen stays black while it is 1
(DRM_MODE_SCALE_FULLSCREEN) when everything works normally.
dmesg doesn't show anything interesting though. Maybe a higher log level,
please give me some hints which component and which debug level you may need.