Steffen Deusch

You really can’t self host a git forge any more. A couple days ago Meta‘s crawler bombarded my forgejo instance and filled the disk with 500+GB of tar archives. Now I took it down because a fleet of residential proxies tries to crawl the Linux repository. Guess I have to set up Anubis after all or move public repos to GitHub… #mobilelinux #pixel9a

It quickly found the gate: an IOVAR named host_access (sounds obvious in hindsight) and a check on it actually receiving a D3 interrupt from the PCIe controller. With that, wifi idles between 10 and 30 mW now. Before we were at ~120mW (associated). There’s the possibility to further lower this by completely stopping the PCIe link and fully retrain it on wake, that’s what Android does. It idles wifi between 0 and 6mW (measured on the rail). All of this in ~1h. 2/2 #mobilelinux #pixel9a

So something that wouldn’t have been possible without LLMs for me: yesterday I debugged BCM4383 wifi host wake, so the host can almost fully power down the bus and still be reachable. There’s a GPIO that triggers an interrupt when the chip wants to wake the host, but I was unable to get it to be activated. So Claude casually patched the Broadcom firmware (approach from Nexmon) to dump the ROM (not accessible over host memory). Then deassmebled the code. 1/2 #mobilelinux #pixel9a

Oh and speaker safety is also working, so it doesn’t even fry your speakers! #mobilelinux #pixel9a

YES! I got the full audio pipeline working and the speakers actually sound great now after struggling with it for a couple of days. A prerequisite for audio was the AoC (the always on compute chip). It also provides access to almost all physical sensors. After reverse engineering the USF (googles AoC sensor framework) and bridging it to IIO, Phosh now properly rotates the screen when rotating the device. A couple more weeks and this could be an actually usable phone! #mobilelinux #pixel9a

There we go! Exynos 5300 with custom ModemManager SIT plugin #mobilelinux #pixel9a

Mobile data works now with some hacks. I also found the reason for a weird modem crash. The modem requests extra carrier data over a separate oem channel in protobuf format. It retries this a couple of times and while it does, data stalls. And if those requests are ignored for too long, an internal queue fills up until the modem crashes hard #mobilelinux #pixel9a

Update: I got the Exynos 5300 modem booting and was able to send a simple text message! Sadly, all very proprietary with no existing integration into e.g. ModemManager #mobilelinux #pixel9a

In-band deep sleep works now too. That drops the idle power usage when connected to wifi (measured WLAN+BT rail only) from nearly 400mW to 130mW. Still too high compared to downstream, but a big improvement. And while both GPT-5.5 and Claude Opus 4.8 were unable to pinpoint previous issues I've had, Fable 5 did nail it in one prompt. Not sure what to think of that... #mobilelinux #pixel9a

So it was more complicated than I thought. And it showed the limits of both Claude Opus and GPT-5.5. Both were unable to pin down the pattern needed to make the card accept the host_cap flag it seems to require for allowing D3 sleep. Then I found a commit message from Asahi Linux about brcmfmac host_cap by good old searching. I thought all the wifi changes from Asahi were upstreamed, but apparently not. Their kernel fork had the exact pattern I needed. Wifi still up after a night asleep!

Ah well, of course enabling WiFi broke sleep again, so back to debugging. Hopefully it’s a small fix.

Big progress, WiFi works now! I'm posting this from the Pixel 9a running #postmarketOS #mobilelinux