DisplayLink
Current version of evdi does not support DP-Alt mode (or chained displaylink chips)
Dear sirs,
according to the specs of my docking-station Startech triple 4K (DK31C3HDPD) 3 monitors should work, but only 2 are adressed. The specs says, that the 3rd 4K display can be adressed, iff the USB3 gen2 has been connected, this is the case.
Hi there. 😇 The third 4k display is provided by DP alt-mode, which requires a USB Type-C interface port. May I ask what is the model of your computer?
Salut, your are right for some Docking-Stations, but this one only reauires a USB3 Gen2 Connection. https://www.startech.com/en-us/cards-adapters/dk31c3hdpd. In contrast, this one needs DP (https://www.startech.com/en-us/cards-adapters/dk31c2dhspd). Anyway my Lenovo ThinkBook 16p G2 ACH Mineral Gre has a USB3 Gen2 connectivity. Some specs says it as a DP, but i am not sure due to the AMD Chipset.
Sometime the logical monitor 1goes over 2 screens, where the secound is useless.
Maybe I am reading something wrong but if you look at the description from the link you provided, it does require DP in order to get three 4k monitors.
HDMI & DisplayPort for Triple Monitor Outputs This USB-C Gen 2 docking station with DP 1.4 and HDMI 2.0 HDR support, is a perfect choice for dual or triple monitor setup, supporting up to triple 4K 60Hz display output, with any combination of three DisplayPort or HDMI video interfaces, on USB-C Gen 2 (with DP 1.4 support) laptops, MacBooks and Windows-based Thunderbolt 3 laptops. Older USB-A laptops will only support dual monitor setup.
Host Display Output USB-C Gen 1 or 2 (with DP 1.4) Triple Display - 3x 4K 60Hz Thunderbolt 3 (DP 1.4 Supported) Triple Display - 3x 4K 60Hz USB-C Gen 1 (with DP 1.2) Triple Display - 2x 4K 60Hz; 1x 4K 30Hz USB-A or USB-C (No DP Alt Mode) Dual Display - 2x 4K 60Hz
Does your USB-C port have the DP symbol next to it?
There are different dockig stations out there, most of them use the DP signed UCB-C connectors to run the 3rd monitor. My AMD-diriven Noteboook has no DP indication, despite the fact that lenovo says that monitors should use the USB-C connectors to attach a monitor and not the USB-A connector on the back. The docking station (the more expensive one) itself does not mention a DP access, but requires a 10Gb USB3.1-C Gen2 connector. My notebook offer two of them on the right handside.
So i figured outto buy the more expensive on with 3 * (HMDI/DP) connector at the back side demmanding a 10Gb USB-3.1 Gen1 connector. There are also some exprensive 4 port docking stations out there, that are capabel to run 4 4K monitors ovr a USB line.
I installed trhe original Lenovo W10 for the AMD on the Lenovo Laptop and i was able to adress 3 of 4K monitor in hight resolution without any problems. In comparison to a professional 4-way 4K card the performance was a bit slower but still fast enough to work with.
The lag was acceptable and the performance with the 10Gb USB-3.1 Gen1 surprisingly good. Last not least,. the CPU consumption was quite low, the 100% and more load (for one CPU) shows, that there is something wrong with evdi on Linux. Maybe the AMD USB code may be not perfect too inside the kernel.
Anyway, i would be happy to these the same performance on linux, cause the usability of a Linux Desktop is better than W10. DisplayLink can you hear me ???? I am a developer, i would like to help!
It seems, that the current evdi driver does not chained display-link adapters. For this reason i changed the title of this topic. It looks like, that StarTech uses more than one DisplayLink chips in order to allow an access of more than 2 4K monitors. This could be an explanation for the support of 3 monitors using the 6000 display-link chip, that officially supports only 2 4K monitors!
The DisplayLink Manage shows this configuration:
[Laptop-1QNO8F8 (Lenovo)]
|
+ --- [USB StarTech DK31C3HDPB]
| +-- 1. LG Ultra HD
| |
| +-- 3. LG Ultra HD
|
+ --- 2. LG Ultra HD
|
+ ---- Native Display (Disconnected)
or is the 2.Lg connected with USB DP-Alt mode? The notobook does not have any sign, indicating, that the USB-C 3.1 support DP Alt mode too?
Anyway evdi does not recognize the 3rd screen.