A few suspected hardware limitations

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Hi Community!

I’ve been playing with Rubik Pi 3 for a few weeks. Tried Qualcomm Linux, Debian and Canonical Ubuntu (Desktop). Here are a few hardware related issues that I’ve encountered, rather than limited to a single OS image, but all of the OSes that I’ve tried. I hope someone from Qualcomm or Thundercomm may see this and clarify.

  1. Suspend to RAM not supported
    This is explictly stated in Ubuntu release notes:

Power Management - Suspend and Resume - Not supported

I’m also not seeing it working in any other OS, so may be hardware limitation. If STR is not possible, I want to know what is the best we can do to put Rubik Pi 3 into a low-power consumption standby mode.

  1. On-board HDMI (1.4) resolution support incomplete

In all cases, I cannot let it output at 1920x1200, which is the resolution of my monitor that I’ve been using daily. As a result, I have to take the usb-c to DP path, which seems to support a broader range of resolutions.

  1. Audio via USB-C to DP
    There seems to be no such an option in any OS.
    @Hongyang.Zhao mentioned this in his “Known issue of Debian System”:
    Debian 系统已知问题 --- - 问题咨询 - RUBIK Pi

Working options are:

  • 3.5 mm jack
  • HDMI (on-board)
  • USB UAC

Since that the on-board HDMI doesn’t support 1920x1200, I’m really interested in wiring audio through the USB-C DP path.

Thanks.

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I’ve just read some previous posts and it seems that #2 is not a hardware limitation but a software issue with Ubuntu & Debian. Expecting fixes.

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Support for 1920×1200 resolution will be introduced in a future release. Should you have any additional requirements or recommended resolutions, please let us know.
If you are able to download and compile the source code, we can also supply the corresponding patch.

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For both the Debian and Ubuntu releases, you may use the systemctl suspend command to initiate suspend-to-RAM.

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6

I’ve just tried “systemctl suspend” in Ubuntu Desktop. My current situation is that, the system suspends shortly, then waken up automatically.

Then I tried

journalctl -b 0 | grep -i “wake”

And there’s:

12月 23 00:08:49 ubuntu kernel: qcom_geni_serial 99c000.serial: wake IRQ with no resume: -13

Which seems to be related to UART

PS. I’m not really sure where to look at to check the reason of the interruption. The above log is picked based on my own opinion, could be wrong.

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Could you kindly confirm whether you are using the latest release? We recommend conducting your tests with the most recent version.
Additionally, could you please let us know what peripherals were connected to the board when you ran the systemctl suspend command—such as power supply, serial cable, or HDMI?

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  • Could you kindly confirm whether you are using the latest release?

Yes. I’ve been doing “sudo apt upgrade” regularly.

  • Additionally, could you please let us know what peripherals were connected…

I got a quite complicated setup in this case. Apart from the PD adapter, I got a few devices connected through a docking station: 2 external drives, 1 Ethernet cable and a few input devices connected by Bluetooth. When I simplified the setup by disconnecting them one by one, the problem was gone at some point, so I can actually narrow it down!

It turned out to be a Bluetooth remote controller that is interrupting. By removing its battery, now I can successfully suspend my Rubik Pi 3.

Thanks for the suggestions!

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Excellent news! Thank you for your response.