[Bug 42490] NUTMEG DP to VGA bridge not working

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=42490

--- Comment #39 from diego.abelenda at gmail.com 2012-09-08 08:59:02 UTC ---
Created attachment 66828
  --> https://bugs.freedesktop.org/attachment.cgi?id=66828
dmesg booting with 2 monitors plugged patch applyed on top of drm-fixes-3.6
drm.debug=4 (X with NoAccel)

I tested a few things and found out that with the patch over drm-fixes-3.6 I
generally get the DVI screen working but the VGA has no signal if it is plugged
during the boot. The generally is there because sometimes I just get a black
screen on the DVI and then X causes a GPU Hangup (The NoAccel suppresses the
Hangup). This situation is rare and If the GPU hangup pressing the reset switch
(instead of letting the machine off during some time and doing a cold boot)
causes it to happen more often.

A "quick" way to do it is booting without the patch starting X without NoAccel
and then pressing the reset button and booting with the patch.

Seems the firmware doesn't reset the state of the card properly during POST or
something. Last night the problem happened "by itself", so it might happen
without trying to provoke it. This morning I tried rebooting a few times but
didn't get it to happen without provoking it.

The attachment is dmesg | grep -e drm -e radeon   when the DVI screen stays
black (VGA saying no signal) and without hangup (provoking it on the previous
boot). The last part is X turning the screens off and trying to wake them up.
The situation didn't change.

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