[Bug 207595] New: [amdgpu] Displayport MST not functional on AMD Stoney

[Bug 207595] New: [amdgpu] Displayport MST not functional on AMD Stoney

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=207595

            Bug ID: 207595
           Summary: [amdgpu] Displayport MST not functional on AMD Stoney
           Product: Drivers
           Version: 2.5
    Kernel Version: 5.4.28, 5.4.36
          Hardware: All
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: Video(DRI - non Intel)
          Assignee: drivers_video-dri@kernel-bugs.osdl.org
          Reporter: jjo.braun@gmail.com
        Regression: No

Created attachment 288939
  --> https://bugzilla.kernel.org/attachment.cgi?id=288939&action=edit
lspci output of Lenovo 14w notebook with stoney gpu

Hello,

I do have some issues running a Lenovo 14w notebook in a multi monitor setup.
The displays are connected as followed:

[Lenovo 14w]--(USB-C)-->[Dell U2719DC]--(Display Port)-->[Some other display]

The second display is not connected directly to the notebook. This display is
connected to the monitor output of the Dell display. The Dell display is
configured to use MST and this setup was successfully validated with a Windows
10 installation.

When I plug the Dell 2719DC with the daisy chained monitor via USB-C to the
notebook, the screens are staying black and I get crash of the amdgpu driver in
dmesg. Kernel logs (5.4.28 and 5.4.36) are attached.

My system is currently based on kernel 5.4.28. But I did checked also the
latest kernel version in the 5.4 LTS tree which was 5.4.36. The same error is
reproducable under Ubuntu 20.04 which is based on kernel 5.4.0.

If MST is disabled in the Dell 2719DC, it works as expected. My intenal
notebook screen is expanded with the USB-C connected Dell U2719DC. And the
third monitor is in clone mode with the Dell U2719DC.

Thank you for reading and kind regards,
Johannes Braun

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[Bug 207595] [amdgpu] Displayport MST not functional on AMD Stoney

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=207595

--- Comment #1 from Johannes Braun (jjo.braun@gmail.com) ---
Created attachment 288941
  --> https://bugzilla.kernel.org/attachment.cgi?id=288941&action=edit
Kernel log with connected display

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[Bug 207595] [amdgpu] Displayport MST not functional on AMD Stoney

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=207595

--- Comment #2 from Johannes Braun (jjo.braun@gmail.com) ---
Created attachment 288943
  --> https://bugzilla.kernel.org/attachment.cgi?id=288943&action=edit
kernel config 5.4.28

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[Bug 207595] [amdgpu] Displayport MST not functional on AMD Stoney

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=207595

Johannes Braun (jjo.braun@gmail.com) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
 Attachment #288939|lspci output of Lenovo 14w  |5.4.28: lspci output of
        description|notebook with stoney gpu    |Lenovo 14w notebook with
                   |                            |stoney gpu

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[Bug 207595] [amdgpu] Displayport MST not functional on AMD Stoney

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=207595

Johannes Braun (jjo.braun@gmail.com) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
 Attachment #288941|Kernel log with connected   |5.4.28: Kernel log with
        description|display                     |connected display

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[Bug 207595] [amdgpu] Displayport MST not functional on AMD Stoney

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=207595

Johannes Braun (jjo.braun@gmail.com) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
 Attachment #288943|kernel config 5.4.28        |5.4.28: kernel config
        description|                            |5.4.28

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[Bug 207595] [amdgpu] Displayport MST not functional on AMD Stoney

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=207595

--- Comment #3 from Johannes Braun (jjo.braun@gmail.com) ---
Created attachment 288945
  --> https://bugzilla.kernel.org/attachment.cgi?id=288945&action=edit
5.4.36: kernel config

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[Bug 207595] [amdgpu] Displayport MST not functional on AMD Stoney

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=207595

Johannes Braun (jjo.braun@gmail.com) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
 Attachment #288943|5.4.28: kernel config       |5.4.28: kernel config
        description|5.4.28                      |

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[Bug 207595] [amdgpu] Displayport MST not functional on AMD Stoney

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=207595

--- Comment #4 from Johannes Braun (jjo.braun@gmail.com) ---
Created attachment 288947
  --> https://bugzilla.kernel.org/attachment.cgi?id=288947&action=edit
5.4.36: lspci output of Lenovo 14w notebook with stoney gpu

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[Bug 207595] [amdgpu] Displayport MST not functional on AMD Stoney

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=207595

--- Comment #5 from Johannes Braun (jjo.braun@gmail.com) ---
Created attachment 288949
  --> https://bugzilla.kernel.org/attachment.cgi?id=288949&action=edit
5.4.36: Kernel log with connected display

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[Bug 207595] [amdgpu] Displayport MST not functional on AMD Stoney

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=207595

Alex Deucher (alexdeucher@gmail.com) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |alexdeucher@gmail.com

--- Comment #6 from Alex Deucher (alexdeucher@gmail.com) ---
Are you trying to use more than two total displays (including the laptop
panel)?  Stoney only has two display controllers so it can only driver a
maximum of two displays.

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[Bug 207595] [amdgpu] Displayport MST not functional on AMD Stoney

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=207595

--- Comment #7 from Johannes Braun (jjo.braun@gmail.com) ---
Yes, the plan was to use three displays in total. I was not aware that this is
not possible with Stoney. Thank you for the clarification.

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[Bug 207595] [amdgpu] Displayport MST not functional on AMD Stoney

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=207595

--- Comment #8 from Johannes Braun (jjo.braun@gmail.com) ---
Is there a way to ask the amdgpu driver how much displays are supported, e.g.
via a parameter in userspace?

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[Bug 207595] [amdgpu] Displayport MST not functional on AMD Stoney

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https://bugzilla.kernel.org/show_bug.cgi?id=207595

--- Comment #9 from Alex Deucher (alexdeucher@gmail.com) ---
You can ask any KMS driver via the drmModeGetResources() function call in
libdrm.

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[Bug 207595] [amdgpu] Displayport MST not functional on AMD Stoney

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https://bugzilla.kernel.org/show_bug.cgi?id=207595

--- Comment #10 from Alex Deucher (alexdeucher@gmail.com) ---
If using X, you can also use `xrandr --verbose` to see number of crtcs.

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