alt Hacker NewsSorry, I was digging on that too much time ago and haven't saved any links. AFAIR, there is permanent busy state in certain conditions when functioning in SPI slave mode, unablility to reset TXFIFO/RXFIFO and some edge case with DMA and TXE/BSY when DMA failed and you don't know how many bytes are in RxFIFO.
Someone's in the Embassy matrix channel currently trying to figure out why the SPI driver is preventing the USB peripheral from enumerating on their G0…