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If I plug in my 1920x1080 HDMI monitor before starting up my Lenovo E325 (AMD E-350 / HD6310) laptop, everything works fine. However, if I plug in the HDMI cable when in the login screen or later, the screen resolution is capped at 1600x1200. Correspondingly, if I plug in another external 1600x1050 display, it's capped to 1400x1050. The laptop display panel has a resolution of 1366x768. I'm running the latest driver from fglrx-updates.

What I've found out so far:

  • xrandr does not show the correct mode at all. The active, wrong resolution is listed as number 1 in the list.
  • looking at tail -f /var/log/Xorg.0.log shows a hotplug event when the panel is plugged in. A few seconds after, a list of "DDC gathered" modelines is reported, with the native 1920x1080 display resolution being first.
  • If the panel is plugged in when booting, the same log says "Printing probed modes" instead.
  • fglrx(0) also logs that the wrong mode is #0 of "Supported standard timings", so the problem might be that the driver does not choose from the correct list of modes.
  • Disconnecting and replugging the cable does not lower the maximum resolution.
  • The problem is not dependent on the desktop environment. It occurs both in the default Unity install and Cinnamon.

How should I proceed to troubleshoot the problem, or how can I fix it, if there's an easy solution (plugging in the monitor before booting is not in this case)?

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