Re: 5.6 DP-MST regression: 1 of 2 monitors on TB3 (DP-MST) dock no longer light up

From: Hans de Goede <hdegoede@redhat.com>
To: Alex Deucher <alexdeucher@gmail.com>,
	"Lipski, Mikita" <mikita.lipski@amd.com>
Cc: intel-gfx <intel-gfx@lists.freedesktop.org>,
	"dri-devel@lists.freedesktop.org"
	<dri-devel@lists.freedesktop.org>
Subject: Re: 5.6 DP-MST regression: 1 of 2 monitors on TB3 (DP-MST) dock no longer light up
Date: Wed, 26 Feb 2020 18:52:34 +0100	[thread overview]
Message-ID: <77b812d5-5b87-49b7-87dc-16d50a5666df@redhat.com> (raw)
In-Reply-To: <CADnq5_MjaOD+QrupjQwjdu-MgVZm1sg1x9=4uxdv92u1xuSdvQ@mail.gmail.com>

Hi,

On 2/26/20 5:05 PM, Alex Deucher wrote:
> On Wed, Feb 26, 2020 at 10:43 AM Hans de Goede <hdegoede@redhat.com> wrote:
>>
>> Hi,
>>
>> On 2/26/20 4:29 PM, Alex Deucher wrote:
>>> On Wed, Feb 26, 2020 at 10:16 AM Hans de Goede <hdegoede@redhat.com> wrote:
>>>>
>>>> Hi Lyude and everyone else,
>>>>
>>>> Lyude I'm mailing you about this because you have done a lot of
>>>> work on DP MST, but if this rings a bell to anyone else feel
>>>> free to weigh in on this.
>>>
>>> Might be a duplicate of:
>>> https://gitlab.freedesktop.org/drm/amd/issues/1052
>>
>> Looks like you are right, reverting the commit which the bisect
>> from that issue points to:
>>
>> cd82d82cbc04 ("drm/dp_mst: Add branch bandwidth validation to MST atomic check")
>>
>> Fixes the issue for me. I will add a comment to the issue.
>>
>> Note I'm using integrated Intel gfx, so that means that this issue
>> definitely is not amdgpu specific.
>>
> 
> I'm not too familiar with the mst code, but I wonder if we were
> exceeding the bandwidth limits in some setups and it just happened to
> work, but now that we enforcing them, they don't which is correct, but
> a regression from some users' perspective?

I seriously doubt that is the case according to:
https://support.lenovo.com/nl/en/solutions/pd029622

The gen 2 tb3 dock can handle 2 external
displays at 3840*2160@60Hz together with the internal
panel being on and both my external displays run at
1920x1080@60 so I'm consuming less then half of the
maximum bandwidth.

There definitely is a bug somewhere in the
cd82d82cbc04 ("drm/dp_mst: Add branch bandwidth validation to MST atomic check")
commit (or somewhere else and triggered by that commit).

Regards,

Hans

> 
> Alex
> 
> 
>> Regards,
>>
>> Hans
>>
>>
>>
>>
>>>> I'm currently using a Lenovo X1 7th gen + a Lenovo TB3 gen 2 dock
>>>> as my daily rider for testing purposes. When 5.6-rc1 came out I
>>>> noticed that only 1 of the 2 1920x1080@60 monitors on the dock
>>>> lights up.
>>>>
>>>> There are no kernel errors in the logs, but mutter/gnome-shell says:
>>>>
>>>> gnome-shell[1316]: Failed to post KMS update: Page flip of 93 failed
>>>>
>>>> With 93 being the crtc-id of the crtc used for the monitor which is
>>>> displaying black. Since then I've waited for 5.6-rc3 hoping that a
>>>> fix was already queued up, but 5.6-rc3 still has this problem.
>>>>
>>>> gnome-shell does behave as if all monitors are connected, so the
>>>> monitor is seen, but we are failing to actually send any frames
>>>> to it.
>>>>
>>>> I've put a log collected with drm.debug=0x104 here:
>>>> https://fedorapeople.org/~jwrdegoede/drm-debug.log
>>>>
>>>> This message stands out as pointing to the likely cause of this problem:
>>>>
>>>> [    3.309061] [drm:intel_dump_pipe_config [i915]] MST master transcoder: <invalid>
>>>>
>>>> Regards,
>>>>
>>>> Hans
>>>>
>>>> _______________________________________________
>>>> dri-devel mailing list
>>>> dri-devel@lists.freedesktop.org
>>>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>>>
>>
> 

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