Created attachment 88936 [details]
dmesg output

X11 doesn't work on my dual-graphics AMD laptop with kernels 3.10.X - 3.12.X, on 3.9.X and earlier kernels does.
Upon startup lxdm shows a garbage instead of normal picture (but the colors are from the picture), X restarts every few seconds, but kernel itself works fine - I can ssh into the comp or restart using the magic key.
Have been trying different combinations: EXA/Glamor, various xorg options with basically the same result: in some cases I can see the normal working mouse over the garbage, in some cases I get "GPU stall" message in dmesg, or EQ overflow in Xorg.0.log...
R600_DEBUG=sdsafemath - improves a picture a bit;
ColorTiling off - makes things even better - in this case about 70% of the screen are drawn correctly, but at wrong position on the screen;
NoAccel on - works as with 3.9.X kernel - windows and lxdm screen - ok, background with errors.

Created attachment 88937 [details]
Xorg.0.log

Created attachment 88939 [details]
lspci output

(In reply to comment #1)
> X11 doesn't work on my dual-graphics AMD laptop with kernels 3.10.X -
> 3.12.X, on 3.9.X and earlier kernels does.

Can you bisect with git?

Yes, within few  days...

Created attachment 89177 [details]
bisect log with some comments added

Alex,
here is a bisecting results. 
Please note that few commits away from the first bad commit it became half-broken - background isn't corrupted but lxdm doesn't start, and x keeps restarting.

Alex?
Did I provide all necessary information, don't I?

(In reply to comment #7)
> Alex?
> Did I provide all necessary information, don't I?

Yes.  thank you.  I haven't had a chance to look into this in depth yet.

Mr. Deucher?
Is there any chance for a Christmas gift?

This might be a duplicate of bug 60389.  Does attachment 90957 [details] [review] help?

Created attachment 91088 [details] [review]
possible fix

You might also try this patch in combination with the previous one if it doesn't work.

Unfortunately neither 1st one nor the combination of the two helped.
It just reshaped the garbage, and X still keeps restarting.
But now it looks like the screen is divided in small tiles that are maybe correct by themselves but placed at wrong positions and repeated now and then.

UPD: Tried to set ColorTiling and ColorTiling2D to off.
In this case about 60% of the screen is rendered correctly but is placed @ wrong position on the screen. Mouse works but X restarts just the same.

-- GitLab Migration Automatic Message --

This bug has been migrated to freedesktop.org's GitLab instance and has been closed from further activity.

You can subscribe and participate further through the new bug through this link to our GitLab instance: https://gitlab.freedesktop.org/drm/amd/issues/401.