It looks like their are also two modes in your EDID for your panel:

[  1248.508] (II) RADEON(0): Supported detailed timing:
[  1248.508] (II) RADEON(0): clock: 138.8 MHz   Image Size:  282 x 165 mm
[  1248.508] (II) RADEON(0): h_active: 1920  h_sync: 1966  h_sync_end 1996
h_blank_end 2080 h_border: 0
[  1248.508] (II) RADEON(0): v_active: 1080  v_sync: 1082  v_sync_end 1086
v_blanking: 1112 v_border: 0
[  1248.508] (II) RADEON(0): Supported detailed timing:
[  1248.508] (II) RADEON(0): clock: 92.5 MHz   Image Size:  282 x 165 mm
[  1248.508] (II) RADEON(0): h_active: 1920  h_sync: 1966  h_sync_end 1996
h_blank_end 2080 h_border: 0
[  1248.508] (II) RADEON(0): v_active: 1080  v_sync: 1082  v_sync_end 1086
v_blanking: 1112 v_border: 0

[  1248.508] (II) RADEON(0): Modeline "1920x1080"x60.0  138.78  1920 1966 1996
2080  1080 1082 1086 1112 -hsync -vsync (66.7 kHz eP)
[  1248.508] (II) RADEON(0): Modeline "1920x1080"x40.0   92.52  1920 1966 1996
2080  1080 1082 1086 1112 -hsync -vsync (44.5 kHz e)

perhaps one of the modes is problematic.