Hi, * John Ogness <john.ogness@xxxxxxxxxxxxx> [230602 10:13]: > Unfortunately next-20230601 also brought in a series that added > spinlocking to the 8250 driver. That may be the issue here instead. I think you're off the hook here with the spinlocking changes :) My guess right now is that 8250_mtk does not want runtime PM resume called on probe for some reason, and assumes it won't happen until until in mtk8250_do_pm()? Looking at the probe, the driver does pm_runtime_enable(), but then calls mtk8250_runtime_resume() directly. Not sure what the intention here is. Maybe adding pm_runtime_set_active() in probe might provide more clues. When we add the new serial_ctrl and serial_port devices, their runtime PM functions propagate to the parent 8250_mtk device. And then something goes wrong, well this is my guess on what's going on.. To me it seems the 8250_mtk should just do pm_runtime_resume_and_get() instead of mtk8250_runtime_resume(), then do pm_runtime_put() at the end of the probe? I don't think 8250_mtk needs to do register access before and after the serial port registration, but if it does, then adding custom read/write functions can be done that do not rely on initialized port like serial_out(). Looking at the kernelci.org test boot results for Linux next [0], seems this issue is somehow 8250_mtk specific. I don't think the rk3399 boot issue is serial port related. Regards, Tony [0] https://linux.kernelci.org/test/job/next/branch/master/kernel/next-20230602/plan/baseline/
