PinePhone modem keeps "disappearing"
[UPDATE: TL;DR: The resolution is that the hardware is faulty (in fact, not just the modem, but the entire USB subsystem except charging), and that I just bought a new PinePhone which works.]

Since late December (so for the last 3 weeks or so), I have been struggling with a strange issue on my PinePhone (Beta Edition). The modem keeps going down for some reason, making it just "disappear" from the PinePhone's point of view. eg25-manager tries to restart it, and sometimes it succeeds, but often the restart also fails, or eg25-manager gets stuck waiting for a long time and does not even try a reset even though the modem device is not visible to ModemManager or anything else (I cannot even see the device node). Sometimes, the modem does not even come up on boot, and even rebooting several times does not necessarily fix it.

It did happen in the past (before December) that the modem had to be restarted, but that was around once a day, and the auto-restart (in eg25-manager and ModemManager) had been just working for weeks now. (And I believe that was a known issue, which is also why the auto-restart had been implemented.) But now, the modem often goes down every 5 minutes, and the auto-restart does not reliably work anymore either. (Sometimes it does, often it does not.)

The first thing I would have suspected would be the latest software updates. (I run Manjaro Plasma Mobile, the one that was preinstalled on the Beta Edition, but continuously upgraded from the stable repository using pamac-gtk. FYI, Discover is just broken for system updates on Manjaro, so I gave up on using that one long ago, but that is not the issue here.) But if that were the case (i.e., if it were a software regression), the issue would have hit more users, would it not? Yet, I have not seen any other report of this happening. Or does anybody else see the same thing?

The behavior looks a lot like a wrong contact on the USB connection, but the modem is soldered onto the mainboard, is it not? So how can it possibly make a loose contact?

The remaining suspect then was the battery, also considering that the PinePhone modem is connected directly to the battery on the PinePhone. So I bought a replacement battery (a Samsung EB-BJ700CBE, which is documented as fitting) from a local retailer today. And well, yes, the battery fits, and yes, the battery works in principle. But the modem issue is the same whether I use the replacement battery or the original PinePhone battery (that I have now put back in), it makes no visible difference.

So at this point, I am stuck. I am completely out of ideas.

I am pretty annoyed at this point because I was using the PinePhone as my daily driver just fine, but now this issue makes it extremely unreliable (since without the modem, it is really just a tablet!) and I have no idea how to resolve the issue.

Messages In This Thread
PinePhone modem keeps "disappearing" - by Kevin Kofler - 01-17-2023, 05:50 PM

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