Ubuntu 16.10 / early 2011 MacBook Pro(8,2) - displayport link status failed

[Mattt]

Greetings all,

I'm running Ubuntu 16.10 (kernel 4.8.0-26-generic) on an early 2011 MBP (8,2). This has hybrid graphics, but I'm only presently concerned with the AMD Radeon HD 6490M...

I'm trying to connect an external display via an adapter connected to the ThunderBolt port. It works just fine under OSX / MacOS. When I attempt same under Ubuntu, I'm getting "displayport link status failed" and "clock recovery failed". The system (xrandr et al) can see that there's something plugged into the ThunderBolt / DP, but can't identify it (no display model name, incorrect resolution/s, etc). Moving windows across to the (blank) external display works - as in, the mouse and window can go all the way off the laptop's display panel. The external display, just to be clear, remains in suspend / sleep mode. Turning it off and back on results in a brief "no signal" message until it goes back into standby mode.

I've tried two very different displays, and tried both connected via both VGA and DVI cables. Results are always the same.

Relevant kernel boot flags are "i915.modeset=0 radeon.modeset=1 radeon.dpm=1". I've tried radeon.audio=0 and radeon.auxch=0 (and also without DPM) but neither helped.

The machine otherwise runs nicely, either on the Intel or Radeon GPUs.

Any ideas?

Cheers,
Mattt.

[Mattt]

Hey debianxfce,

Yeah, I tried "ForceThingsToWorkTheWayTheyAreMeantTo = 1", and even "ForceDriversNotToBeBroken = 1". Neither worked.

Extensive Googling has failed to help either. Most such issues involve software a lot older than the OS / driver I'm using, and most were resolved (via methods not relevant to my problem - many were driver issues (bugs) which were subsequently rectified by the developers)...

Cheers,
Mattt.

[bridgman]

Just to narrow things down a bit, is the DP portion of the Thunderbolt port connected to the Intel IGPU or AMD DGPU ? Your post suggests it's connected to the AMD GPU but in a hybrid graphics setup I would have expected it to be connected to the Intel iGPU (unless the Intel parts at the time didn't have suitable DP support).

If it is connected to the AMD GPU then my first thought would be to try a kernel driver built with DAL enabled, since AFAIK the DAL DP code is more advanced than the upstream non-DAL code. Could be either the kernel driver DKMS package from AMDGPU-PRO (in which case you'll want to be running 16.04 rather than 16.10 for sure) or a build from the 4.7 staging branch tree that agd5f posts in his repo (which might be new enough to work with 16.10... newer GFX drivers than 16.10 but 4.7 kernel rather than 4.8).

[bridgman]

Mattt, tried to respond but got auto-moderated

[Mattt]

Hey Bridgman,

Yiup - on these MacBooks it's the discrete GPU that's connected to the DP. Even Apple say that dynamic switching must be enabled to allow the use of an external display (in OSX / MacOS, disabling dynamic switching forces the IGP)...

Thanks for your pointers - I'll look into those options today. Certainly more playing around than I wanted to undertake, but I'm pretty determined to get Linux on this thing and finally run it the way *i* want ;-)

Cheers,
Mattt.

[Mattt]

Bridgman,

Damn - seems my GPU (Advanced Micro Devices, Inc. [AMD/ATI] Seymour [Radeon HD 6400M/7400M Series]) is not compatible with amdgpu :-(

Cheers,
Mattt.

[agd5f]

The thunderbolt chipset used by these systems is not properly supported yet in Linux.

[Mattt]

Hey agd5f,

Is this a regression? Folk have successfully used it with the (open) radeon driver before today - just that they've used much earlier versions of it (and Ubuntu), so I was rather hoping to use the current stuff...

Cheers,
Mattt.

[bridgman]

Damn - seems my GPU (Advanced Micro Devices, Inc. [AMD/ATI] Seymour [Radeon HD 6400M/7400M Series]) is not compatible with amdgpu :-(

Sorry, I missed that it was a 6490...

[Mattt]

Hmm... agd5f's comment seems to have put me on the right track, at least...

It would appear that plugging a mini-DP display directly into the TB port would (likely) work - and is thus likely what others have been doing to successfully get an external display working on this model (and ones like it) in the past. The problem appears to be when using the port as TB as I am attempting (with a TB to VGA / DVI / HDMI adapter).

This is a real pity as a) I really need the external display as I'm working away from my main desk (with 23", 24" and 32" displays) around 50% of the time these days; b) I don't have a DP display at my disposal and am loathe to buy one in case it still doesn't work, and c) I very, very much dislike OSX / MacOS - I can't even adjust the overall system font size/s to suit my aging eyes (and that's just one of the many problems I have with it).

Ubuntu 16.10 is otherwise working *very* well on this machine - aside from a little playing around for the UEFI implementation and possibly graphics switching (which I can live without anyways), everything has Just Worked out of the box. It also already out-performs OSX / MacOS by a fair margin (and I haven't "tuned" anything yet). As such, I'll keep on plugging away with it - and if I really can't have an external display at this stage, I'll perhaps hobble together a desktop PC for my other, part-time desk with some components I have sitting around...

Cheers,
Mattt.