Hi all,
I bought a Pixel 8 Pro during Black Friday and after checking everything works on stock, installed GrapheneOS. It was a smooth process and the system works mostly fine, thanks to all developers!
However, I noticed a strange behavior with GPS. The device doesn't seem to be able to find a single GPS satellite. I'm using the GPSTest app, tried all 3 options "Inject PSDS data", "Inject time data", and "Clear assist data" in various orders, with no effect.
I checked 1) wifi only in airplane mode, 2) modem enabled without a SIM card, 3) modem enabled with an unlocked SIM card. Also tried setting the SUPL and PSDS server options to "Standard server" from "GrapheneOS Proxy", but the result was the same. Finally, checked all combinations of the above options with a VPN as well.
There are reasonably-looking messages in logcat, like the below.
I libgps : [proxy_gnss_measurement_callback] called
D GnssPsdsAidl: injectPsdsData: psdsType: 1, psdsData: 172974 bytes
Now, here comes the catch: I reinstalled the latest stock OS (November release at the time a few days ago: husky AP3A.241105.007) and the same GPSTest app worked as expected. I thought I can try again, so I flashed GrapheneOS again, and the GPS was working. Now a few (I think 2) days have passed, and GPSTest is back to showing zero satellites, even after minutes of keeping the device in the same spot (outside, where stock OS got a lock on the location in half a minute).
My assumption, but it might be a long shot, is that the GPS chip is caching some (PSDS? AGNSS?) data and keeps it even when the OS is reflashed, but forgets it after some time.
I'd be happy to hear any suggestions on how to start debugging this further.
Thanks in advance!