https://bugzilla.kernel.org/show_bug.cgi?id=66341
--- Comment #4 from Alex Deucher alexdeucher@gmail.com --- It looks like maybe you have a loose or bad connection to the LCD panel. As you can see in your log, the driver isn't even detecting a panel:
[drm] Radeon Display Connectors [drm] Connector 0: [drm] VGA-1 [drm] DDC: 0x7e40 0x7e40 0x7e44 0x7e44 0x7e48 0x7e48 0x7e4c 0x7e4c [drm] Encoders: [drm] CRT1: INTERNAL_KLDSCP_DAC1 [drm] Connector 1: [drm] HDMI-A-1 [drm] HPD1 [drm] DDC: 0x7e60 0x7e60 0x7e64 0x7e64 0x7e68 0x7e68 0x7e6c 0x7e6c [drm] Encoders: [drm] DFP1: INTERNAL_UNIPHY