Open Source Summit North America 2025

While working with the RADXA ROCK 5B, a low-cost/high-performance RK3588 aarch64-based development board, we discovered that it is picky concerning the used USB Type-C power source. What was rather strange is that while it worked on our upstream Linux kernel (at the time of writing v6.13.1) based Embedded Linux system, it just boot-looped running RADXA's Debian (using a Rockchip downstream v6.1 based kernel). At the same time, my colleagues were working on the Testing in a Box version 2 (TIABv2) integrating USB Type-C power delivery which we plan to use in our board farm once ready. Of course, as soon as they had prototypes I gave it a try and it also showed the problem. By chance, both sides are using the exact same onsemi FUSB302B programmable USB Type-C controller with power delivery. The TIABv2 one is configured as a power source and the ROCK 5B one is configured as a power sink. This talk introduces the USB Type-C power delivery topic and then discusses how we joined forces and debugged both sides, at times giving the ball to the TIABv2 firmware, at other times to the Linux kernel fusb302 driver and back and forth again.