Imac Radeon HD 4850 switch "Mini Display Port" output during install resulting black screen

[artik]

I tried to install Lucid on the new Apple Imac27" with ATI radeon HD 4850 video card. After selected "install", the screen goes black. few investigations later, I discovered display output switch to the Mini Display Port. So, I tried to connect a second screen, and I was right : just after select "install lucid", the video output switch to the second screen, and the main screen turn black.

I continue my installation using my 2nd screen (connected to the mini display port), and after it, I'm on the desktop. I activate Open radeon drivers, they works perfectly, but in the second screen (Vsync is perfect, and very smooth using compiz). Impossible to switch to the main screen. It's not recognized, and stay black.

I tried proprietary ati drivers (10.6). With them, I can activate my main screen, but they are not better than the open ones : there is a big vsync bug. Actually, It's totally impossible for a normal user to use open ati drivers on the main screen with an Imac27 and ati radeon 4850 graphic card.

I think issue is in the kms driver, I tried to deactivate them. Main screen is recognized, but impossible to turn it on, it stay black, and Vsync issue re-appear on the second screen. Maybe the open radeon drivers also got a bug, cause after deactivate them, my main screen is now recognized on display manager, but impossible after activate it, it stay black => back to proprietary drivers, and the Vsync issue)

i tried 2.6.32, 2.6.34, 2.6.35 rc1 released, bug is still here.

[Peter T Hayward (energonic)]

I've been suffering this problem on my new iMac 21.5 (11,2 i3, Radeon 4670). All linux live CDs would give black screen even though I could hear the disc loading up.

I've got round the problem for my system by doing two things:
1 connecting an external monitor through the Mini Display port.
2 Using F6 on the grub boot menu to add options - radeon.modeset=0 nomodeset

I don't know if the radeon modesetting works on the external monitor (LG1710, has worked OK on a Mac Mini but will test it on iMac) but it certainly doesn't work on the main monitor.
I've only tried live CDs so far; in 'xrandr' the main monitor is identified as eDP-0 and it lists the full range of supported resolutions up to 1920x1080.

[Peter T Hayward (energonic)]

Radeon modesetting does not work on my LG1710. I can only get it to light up if I use the two options above.

[MountainX (dave-mountain)]

This issue is affecting me too. I verified that this is the exact behavior I'm seeing with my iMac 11,1. This issue does not affect all model iMacs. Mine is a 27" late 2009 model.

Here is how to check the serial number to determine the model.

On the bottom of your iMac stand, you'll find a label with the serial number printed on it, or from the Apple menu, choose About This Mac. Configure To Order (CTO) models are designated with an asterisk (*). Check the last three characters on the serial number:
iMac (Mid 2010)
DAS, DNM* iMac (21.5-inch, Mid 2010)
DB7, DNN* iMac (21.5-inch, Mid 2010)
DB6, DNP* iMac (27-inch, Mid 2010)
DB5, DNR* iMac (27-inch, Mid 2010)
iMac (Late 2009)
5PC, B9U, CY8* iMac (21.5-inch, Late 2009)
5PK*, B9S* iMac (21.5-inch, Late 2009)
5PE, 5PJ, CYB* iMac (27-inch, Late 2009)
CYC*, 5PM*, 5RU* iMac (27-inch, Late 2009)

[Richard Holmes (richholmes)]

I believe I have the same problem with a Mid 2010 21.5-inch iMac (serial ends in DAS). Trying to boot from a Mint 10 Live DVD, screen goes black early in the boot process. If I put 'nomodeset' or 'radeon.modeset=0' on the boot line I see text until after the "welcome to Linux Mint" message, command line prompt appears, then after some delay it goes to black screen again. If I put 'text' on the boot line I can boot into text mode and text display remains visible. I do not have an external display readily available to check if output is switching there.

[Peter T Hayward (energonic)]

Now using ubuntu natty 11.04 Alpha3 (was using maverick 10.10).

I have established that my main physical screen (iMac display) is detected by the OS radeon driver as output eDP-0, name 'Color LCD', and it is connected but not lit. The external physical screen is detected as output DisplayPort-0, name 'L1710B', and is connected *and* is lit.
Both these outputs are connected to logical (X) screen 0 and they both fit into the viewport of 1920x1080.

If I let KMS set up the graphics it sets DisplayPort-0 to have resolution 1920x1080 (it should be 1280x1024). The kernel modesetting seems to get confused between the two display ports, using the resolution of eDP-0 and assigning it to DisplayPort-0, but then disabling the eDP-0 for some reason.

If I use 'nomodeset' at boot then DisplayPort-0 gets resolution 1280x1024 (correct). This is probably the result of radeon driver probe.

Since it is possible to show terminal output on the iMac display before X starts I suspect that X (or the radeon driver) switches off this output as not being usable.

To me the question is why does the eDP-0 output get switched off? The logs do not offer much except

...
(EE) Radeon(0): channel eq failed: 5 tries
(EE) Radeon(0): channel eq failed
(EE) Radeon(0): clock recovery reached max voltage
(EE) Radeon(0): clock recovery failed
....

perhaps the radeon driver fails to establish the clock frequency for the monitor (iMac display) and switches it off as a precaution against damage?

Earlier I used the ati proprietary driver on ubuntu 10.10 and that worked when driving the iMac display, so it is possible, just not with the OS radeon driver (yet).

[Andy Whitcroft (apw)]

@Peter -- would you be able to get a boot with drm.debug=0x4 on the kernel command line, I think its F6 in the installer which lets you add those kinds of things (on the menu with nomodeset). We would then want the dmesg log for that boot. Thanks.

[paniq (paniq)]

I have a similar problem, although it does not seem to be related to the video card.

The setup is a MacBook 8,1 running Ubuntu 11.04 connected to a 27" iMac via a crosslink Mini DisplayPort cable. The iMac mirrors output when the GRUB screen is reached, but then remains black for the rest of the session.

When starting Ubuntu in Unity mode with effects enabled, the MacBook fails to update the screen once the iMac is connected. It either goes black or freezes, with the cursor still intact. The iMac remains dark.

When starting Ubuntu in classic mode without effects, the MacBook screen works as usual without freezing. When the display port is plugged in, the display goes blank for a second, but then returns properly. Yet, the iMac remains dark.

Still, the iMac is properly recognized. Via the "Monitors" configuration dialog, I can set its proper resolution and arrange it, yet it doesn't react.

The video card is an Intel one - I can't get the exact model right now, but the responsible kernel module is called "i915".

[paniq (paniq)]

I noticed that my problem may not fit this bugs description, so I filed a separate bug #790126 for it.

[Peter T Hayward (energonic)]

Apologies to Andy for not seeing his request on 12 April. I haven't had notification and I've moved on since then.
Currently running 11.04 (Unity desktop) on iMac i3 (21.5"). An update to fglrx and amdcc seemed to fix the display port problem. All runs well on main screen, full resolution. Cannot set up dual monitor with extended desktop though.
I triple boot my system and I can get Archlinux, with recent (11.3) catalyst drivers, to drive both screens as extended desktop.
11.3 was the first driver to recognise the two monitors correctly.
I think ubuntu video is a bit more choppy than Arch. Most ubuntu videos have flashing block artefacts. Also kde is a bit smoother than gnome desktop.

[artik (jeff-artik)]

Hi Peter,

yes, but this solution force us to use proprietary drivers. There is no solution using radeon drivers on my Imac 27", I5.

[Douglas Bauer (doug-bauer)]

This exact issue is affecting me as well. Is there anyone currently pursuing a solution?

I would love to get involved in the process, I am available for testing and troubleshooting almost any time.

Are there any switches to plug into the installation that would force Ubuntu installer to use Display0 as the screen and not MDP?

[Nicolas Jungers (unbug)]

I still have the same issue with Oneiric. It happens with ubuntu-server and kubuntu (both beta 2)

[Andrew Paxson (paxsonsa)]

I also have this same problem.
iMac 27" (late 2009)
4 Gb RAM
1 TB
ATI Radeon HD 4850

I have tried everything under the sun. ATi Drivers, Open Source Drivers, and Propretary Drivers. Some methods have brought the screen up but with major tearing and ghosting issues others have not done anything but move the output to my display port. Very Frustrating.

Hopefully a fix is out soon!

[Greg Cornish (graphico)]

I had the same problem installing windows 7 and found this fix. While it may not work on Ubuntu, It may give you some direction. I'm resigned to just use my external monitor for Ubuntu.

[Greg Cornish (graphico)]

Oops

http://support.apple.com/kb/TS3173

[penalvch (penalvch)]

artik, this bug was reported a while ago and there hasn't been any activity in it recently. We were wondering if this is still an issue? If so, could you please test for this with the latest development release of Ubuntu? ISO images are available from http://cdimage.ubuntu.com/daily-live/current/ .

If it remains an issue, could you please run the following command in the development release from a Terminal (Applications->Accessories->Terminal), as it will automatically gather and attach updated debug information to this report:

apport-collect -p linux <replace-with-bug-number>

Also, could you please test the latest upstream kernel available following https://wiki.ubuntu.com/KernelMainlineBuilds ? It will allow additional upstream developers to examine the issue. Please do not test the daily folder, but the one all the way at the bottom. Once you've tested the upstream kernel, please comment on which kernel version specifically you tested. If this bug is fixed in the mainline kernel, please add the following tags:
kernel-fixed-upstream
kernel-fixed-upstream-VERSION-NUMBER

where VERSION-NUMBER is the version number of the kernel you tested. For example:
kernel-fixed-upstream-v3.11-rc5

This can be done by clicking on the yellow circle with a black pencil icon next to the word Tags located at the bottom of the bug description. As well, please remove the tag:
needs-upstream-testing

If the mainline kernel does not fix this bug, please add the following tags:
kernel-bug-exists-upstream
kernel-bug-exists-upstream-VERSION-NUMBER

As well, please remove the tag:
needs-upstream-testing

If you are unable to test the mainline kernel, please comment as to why specifically you were unable to test it and add the following tags:
kernel-unable-to-test-upstream
kernel-unable-to-test-upstream-VERSION-NUMBER

Once testing of the upstream kernel is complete, please mark this bug's Status as Confirmed. Please let us know your results. Thank you for your understanding.

[artik (jeff-artik)]

It's fixed. I switch to this stut.

[Peter T Hayward (energonic)]

Bug still affects me. Any linux behaves the same. When I boot without external monitor, cannot see any terminal, let alone logon screen. Booting with external monitor gets full access to terminals on the external monitor..

[penalvch (penalvch)]

Peter T Hayward (energonic), given this was marked resolved by the original reporter in 2013 (who had different hardware), it will help immensely if you use the computer the problem is reproducible with, and provide necessary debugging logs by filing a new report with Ubuntu via a terminal:
ubuntu-bug linux

Please feel free to subscribe me to it.

[Toby (toby5699)]

I am in the exact same position as Peter T Hayward (energonic). I appreciate that this has been marked as fixed, but how can I go about implementing the fix?
Thank you