Comment 14 for bug 914437

I have a laptop. As soon as I connect my external monitor via HDMI, dmesg provides the following error:

[drm:drm_edid_block_valid] *ERROR* EDID checksum is invalid, remainder is 254
Raw EDID:
    ff ff ff ff ff ff ff ff 1a b3 45 07 01 01 01 01
   21 11 01 03 80 2f 1e 82 2a ee 95 a3 54 4c 99 26
   0f 50 54 a5 4b 00 95 0f 81 80 81 40 71 4f 95 00
   b3 00 81 c0 01 01 21 39 90 30 62 1a 27 40 68 b0
   36 00 da 28 11 00 00 1c 00 00 00 ff 00 59 45 33
   4c 30 31 30 32 36 33 0a 20 20 00 00 00 fd 00 38
   4b 1f 53 0f 00 0a 20 20 20 20 20 20 00 00 00 fc
   00 58 32 32 57 2d 31 0a 20 20 20 20 20 20 00 53
i915 0000:00:02.0: HDMI-A-1: EDID block 0 invalid.

When I connect the external monitor via VGA, it works fine.
The external monitor also used to work fine via HDMI/DVI quite some time ago.

xrandr has the following output (the external monitor in connected by VGA and also by HDMI/DVI):

Screen 0: minimum 320 x 200, current 1600 x 900, maximum 8192 x 8192
LVDS1 connected 1600x900+0+0 (normal left inverted right x axis y axis) 382mm x 214mm
   1600x900 60.0*+
   1440x900 59.9
   1360x768 59.8 60.0
   1152x864 60.0
   1024x768 60.0
   800x600 60.3 56.2
   640x480 59.9
VGA1 connected (normal left inverted right x axis y axis)
   1680x1050 60.0 +
   1280x1024 75.0 60.0
   1440x900 75.0 59.9
   1280x960 60.0
   1152x864 75.0
   1280x720 60.0
   1024x768 75.1 60.0
   800x600 75.0 60.3
   640x480 75.0 60.0
   720x400 70.1
HDMI1 disconnected (normal left inverted right x axis y axis)
DP1 disconnected (normal left inverted right x axis y axis)

So I can't even active the monitor by HDMI (xrandr --output HDMI1 --auto hs no effect).

As anyone found a workaround?