EHCI, USB, LOL, OTG, CBMEM, OMG, CAR. Those have been the topics of my first week of GSoC on the coreboot tree. Dozen or so patches in, same amount waiting on approvals or further actions from me. I was glad to find my mentors with many ideas for refactoring and working actively on reviews. Nice start I would say!
It turned out usbdebug support in coreboot may not be very widely tested, hardware has typically had serial ports available for the same task. With some required bugfixes on cache-as-ram and CBMEM, I now have identical output on usbdebug when compared for CBMEM console and serial console. For my setup, that is. More needs to be done to get AMD boards supported once again. I also get to fix usbdebug receive side to make it a usable pipe for GDB and SerialICE, and I want it to handle USB errors and disconnects gracefully.
On the debugging hardware side things have brightened up quite a bit. While the original Net20DC product is discontinued, I was concerned the only solution is the DIY version pictured on the right. I have then received positive feedback and testing from the community (thanks Denis and Aaron) of using some inexpensive ARM boards as USB debug gadgets. To make them work flawlessy, some modification needs to be done on the USB gadget framework drivers on the kernel side. I should try to find someone already familiar with the gadgets to take this development task as I believe it is of interest for kernel developers too.
Some principal decisions on payloads have been made. I would first add usbdebug support for FILO. I am eagerly waiting for the FILO payload with flashrom to be released, this would gain us methods to program the system flashchip from USB storage, in a pre-os environment.