Librem 5 Hoyoki Dock Video Output Sleuthing

Hello hive brain. I’m attempting to troubleshoot a puzzling operational failure and would appreciate any pointers anyone has in case there’s something huge I am missing here.

The Problem: The Hoyoki CB-C71 USB-C hub I purchased from the Purism store no longer outputs video.

Steps Taken So Far:
Hardware Element Testing

  1. HDMI cables - I have verified that two different HDMI cables I have are good using two separate displays, two different source computers, and a cable tester (I work for an AV engineering firm, so hooray for off-hours use of office supplies!).
  2. Power adapters - I have the USB-C power adapter that came with my L5, which happily charges the phone with or without the Hoyoki dock in place. I also have an 85W Apple power adapter which works with everything I’ve plugged it into.
  3. Displays - I have two separate HDMI displays I’ve successfully used with the L5 in the past that are currently functional and showing content from other sources, using the same cables and same input port.

Librem 5 Diagnostic Investigation
I next wanted to be certain that with the Hoyoki connected to the L5 and the power adapter, there was enough of a power budget to work with.

purism@pureos:~$ cat /sys/class/power_supply/tps6598x-source-psy-0-003f/uevent 

Seems fine there. What does lsusb have to say for itself?

purism@pureos:~$ lsusb
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 004: ID 2020:2060 Qualcomm, Incorporated Qualcomm CDMA Technologies MSM
Bus 001 Device 003: ID 0424:4041 Microchip Technology, Inc. (formerly SMSC) Hub and media card controller
Bus 001 Device 002: ID 0424:2640 Microchip Technology, Inc. (formerly SMSC) USB 2.0 Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 003 Device 008: ID 05e3:0751 Genesys Logic, Inc. microSD Card Reader
Bus 003 Device 006: ID 05e3:0751 Genesys Logic, Inc. microSD Card Reader
Bus 003 Device 010: ID 09eb:0131 IM Networks, Inc. Virtual HID
Bus 003 Device 009: ID 3297:1969 ZSA Technology Labs Moonlander Mark I
Bus 003 Device 007: ID 09ea:0130 Generic Virtual HUB
Bus 003 Device 005: ID 05e3:0610 Genesys Logic, Inc. Hub
Bus 003 Device 004: ID 1a40:0101 Terminus Technology Inc. Hub
Bus 003 Device 003: ID 0bda:8153 Realtek Semiconductor Corp. RTL8153 Gigabit Ethernet Adapter
Bus 003 Device 002: ID 2109:2822 VIA Labs, Inc. USB2.0 Hub             
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

Notably absent from this is any mention of a video adapter.
Do we then conclude that there is an internal hardware failure in the Hoyoki device on the HDMI output side of things? I only have one of those so can’t A/B test with another.

(I also tried this same set of steps with an Anker A3380 hub that I have just to see if it’d work, and not only does that not put out HDMI it won’t even charge the phone - for some reason it seems to be current-limited all the way down to like 0.1A which is not consistent with its spec and I think that might just be down to some sort of hardware handshake problem…)

So yeah. This is what I’ve done so far. Any other steps anyone can think of?

Thanks in advance.


Just to cover some basics, is the dock powered on without the L5 as indicated by the green light?

Do other peripherals like USB ports function when plugged into the dock?

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Yes to both. Interestingly, the user manual for the Hoyoki (which I still have a paper copy of!) recommends connecting it to the host device before connecting anything else, but it doesn’t seem to make a difference whether I connect it to the L5 first or not. The only thing it’s not doing is video.

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I believe that video output does not itself occur via USB i.e. video altmode repurposes some of the USB bandwidth to carry something approximating DisplayPort.

Dare I ask whether you have captured output from lsusb when it did work?

Is a second display showing up in Settings?

Anything from journalctl -b 0 | grep something-appropriate
(and again whether you have captured journal from when it did work)?

Do you have another computer that is capable of video output over USB-C e.g. a Librem 14?

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Sadly no, I don’t have any info to show from when the system did work. The second display does not show up in Settings. My other computer has Thunderbolt out rather than vanilla USB-C, so I’m not sure how comparable that really is.

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