The RS485 implementation for pl011 has its quirks with busy waiting. There's a mainline patch from Miroslav Ondra ("serial: amba-pl011: Fix RTS handling in RS485 mode") that reworks this and aligns the logic with other drivers. It's already included in the rpi-6.18.y branch, so it's worth trying out
https://github.com/raspberrypi/linux/co ... d3383eb1f3
https://github.com/raspberrypi/linux/co ... d3383eb1f3
Statistics: Posted by nicolaiB — Thu Dec 18, 2025 10:59 am