Hi Andre, On 2023-02-21, André Pribil <Andre.Pribil@xxxxxxxxxxxxxxxx> wrote: > I'm using a IMX8MP board with kernel 5.10.165-rt81. UART3 is used as > the console device. When the device boots the serial outputs on this > UART get corrupted at some point. It looks like only one line is > corrupted. However, this line often confuses my terminal, so that the > lines behind are also not shown correctly. A reset of the terminal > fixes that. > > I could not figure out why this happens, yet. I only know that the > issue does not occur when I remove the preempt-rt patch or when I > specify the "maxcpus=1" kernel command line parameter. I also tried to > enable/disable the "earlycon" setting, but this seem to only change > the time when this happens during the boot messages. > > When the boot messages are afterwards displayed with "dmesg", they do > not contain corrupted characters. Therefore, I assume that the > corruption occurs at the UART level. Maybe some lock issue and > therefore some concurrent access to the UART registers? There is a known problem [0] with this printk implementation that it does not support boot consoles. I will follow-up this email with the rebased patch from Petr Mladek, which should work around the issue. Please check if it works for you. John Ogness [0] https://lore.kernel.org/lkml/YrCO04oNncE1xF5K@alley
