Cannot connect Apple Cinema Display through DisplayPort

Framework Laptop 13 Linux
1

I have an Apple Cinema Display (model A1081) connected to a DVI-female to HDMI male adapter, which is connected to the Framework 13 Laptop with a DisplayPort Expansion Card (FRACCDBZA 2409202DV, 2nd Gen).

Laptop information:

  • OS: Ubuntu 24.04.1 LTS x86_64
  • Host: Laptop (13th Gen Intel Core) A4
  • Kernel: 6.8.0-51-generic
  • Shell: zsh 5.9
  • Resolution: 1920×1080
  • DE: Plasma 5.27.11
  • WM: kwin
  • CPU: 13th Gen Intel i5-1340P (16) @ 4.600GHz
  • GPU: Intel Raptor Lake-P [Iris Xe Graphics]
  • GPU Driver: i915

The DisplayPort–DVI adapter, when connected to another computer, works as expected. When an HDMI–DVI adapter is used instead of the DisplayPort adapter, the laptop also works well with the display. However, the combination of DisplayPort expansion card and DisplayPort–DVI adapter causes the monitor to stay blank, and the laptop to not recognize it.

The laptop does recognize the DisplayPort adapter on its own, but shows no sign of detecting an external display.

$ lshw -short
H/W path        Device          Class          Description
==========================================================
[...]
/0/100/14                       bus            Alder Lake PCH USB 3.2 xHCI Host Controller
/0/100/14/0     usb1            bus            xHCI Host Controller
/0/100/14/0/2                   input          DisplayPort Expansion Card
/0/100/14/0/3                   input          HDMI Expansion Card
[...]

Below follows the journalctl entries for when the DisplayPort expansion card is inserted into the laptop:

kernel: usb 1-2: new full-speed USB device number 11 using xhci_hcd
kernel: usb 1-2: New USB device found, idVendor=32ac, idProduct=0003, bcdDevice= 0.00
kernel: usb 1-2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
kernel: usb 1-2: Product: DisplayPort Expansion Card
kernel: usb 1-2: Manufacturer: Framework
kernel: usb 1-2: SerialNumber: 11AD1D002180400339310B00
kernel: hid-generic 0003:32AC:0003.0009: hiddev0,hidraw2: USB HID v1.11 Device [Framework DisplayPort Expansion Card] on usb-0000:00:14.0-2/input1
mtp-probe[6964]: checking bus 1, device 11: "/sys/devices/pci0000:00/0000:00:14.0/usb1/1-2"
mtp-probe[6964]: bus: 1, device: 11 was not an MTP device
mtp-probe[6983]: checking bus 1, device 11: "/sys/devices/pci0000:00/0000:00:14.0/usb1/1-2"
mtp-probe[6983]: bus: 1, device: 11 was not an MTP device

and the journalctl entries for when the DisplayPort cable (adapter) is inserted into the expansion card:

kernel: usb 1-2: USB disconnect, device number 11
wpa_supplicant[1268]: wlp170s0: CTRL-EVENT-SIGNAL-CHANGE above=0 signal=-63 noise=9999 txrate=648500
kernel: usb 1-2: new full-speed USB device number 12 using xhci_hcd
kernel: usb 1-2: New USB device found, idVendor=32ac, idProduct=0003, bcdDevice= 0.00
kernel: usb 1-2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
kernel: usb 1-2: Product: DisplayPort Expansion Card
kernel: usb 1-2: Manufacturer: Framework
kernel: usb 1-2: SerialNumber: 11AD1D002180400339310B00
kernel: hid-generic 0003:32AC:0003.000A: hiddev0,hidraw2: USB HID v1.11 Device [Framework DisplayPort Expansion Card] on usb-0000:00:14.0-2/input1
mtp-probe[7092]: checking bus 1, device 12: "/sys/devices/pci0000:00/0000:00:14.0/usb1/1-2"
mtp-probe[7092]: bus: 1, device: 12 was not an MTP device
mtp-probe[7111]: checking bus 1, device 12: "/sys/devices/pci0000:00/0000:00:14.0/usb1/1-2"
mtp-probe[7111]: bus: 1, device: 12 was not an MTP device

On its own, every piece of hardware works, but when combined, the monitor is not detected. I’m not sure whether this is a hardware or OS issue. Any help is appreciated. Thank you!

2

I have a theory as to why this does not work.
Display port has parameters called “Voltage Swing and Pre-emphasis”.
If it does not negotiate these settings correctly, the display screen will not work.
I found a bug in amdgpu driver a while back in kernel 6.6.x that caused the negotiation to not work, and it just choose a fixed value. It would work with some screens and not others. Once the software bug was fixed, it worked with all the screens I had again.

One of the symptoms is that the “Voltage Swing and Pre-emphasis” is not negotiating correctly is that one can swap out the Display port cable with a different one and it starts working. The “Voltage Swing and Pre-emphasis” is there to automatically adapt to varying quality and lengths of Display Port cables.

So my question is, does anyone have any test equipment that could test the “Voltage Swing and Pre-emphasis” negotiation on the FW display port slot cards.
Maybe it is using a fixed value and not negotiating?

3

Your DisplayPort-DVI adapter may require DP++.

DP++ is a feature where a DisplayPort port can support both the DisplayPort protocol and the HDMI/DVI protocol (HDMI and DVI are the same protocol).

That makes it possible to have much cheaper adapters that simply request the DVI protocol and then connect the wires from the DisplayPort port to the DVI port. Otherwise it would be necessary for the adapter to contain a chip to translate between the two protocols.

The problem is that not all DisplayPort ports are DP++. Framework’s DisplayPort Expansion Card only supports the DisplayPort protocol, which means a DisplayPort to DVI adapter needs to have an active conversion chip.

The HDMI to DVI adapter works because Framework’s HDMI Expansion Card contains an active conversion chip to convert from the DisplayPort protocol to the HDMI protocol.

4

I think the DisplayPort–DVI adapter does have DP++. I was looking up the two protocols, and the adapter has the following mark imprinted on the DisplayPort side:

image
image260×152 4.64 KB

5

DP++ isn’t a feature of adapters.

DP++ is a feature of some DisplayPort ports on computers that makes it possible to use cheaper adapters.

It sounds like your adapter requires a computer that supports DP++, however Framework’s DisplayPort Expansion Card doesn’t support DP++.

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6

I think @Kyle_Reis has the correct answer for you.
DP++ uses a different method to get the video to the screen that allows for “passive” adapters to get the Display Port to HDMI or DVI.
The FW is not DP++, so one needs active adapters to convert from Display Port to DVI or HDMI.
The FW HDMI slot card has the active components in it, so that is why you can plug into the FW HDMI and it works.
The FW Display port slot card does not have the active components in it, so that is why your passive Display Port to DVI adapter is not working. You will need to get an active Display Port to DVI adapter for it to work.

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