Re: [PATCH v2 1/6] serial: sb1250-duart: Fix console message clobbering at channel resets

[Philippe Mathieu-Daudé]

On 25/5/26 01:12, Maciej W. Rozycki wrote:
> Ensure any characters outstanding have been sent before issuing channel
> resets so as to prevent messages issued to the bootconsole from getting
> clobbered.
>
> Contrary to device documentation at the time the transmitter empty bit
> is set only the transmit FIFO has been drained and there is still data
> outstanding in the transmitter shift register, so wait an extra amount
> of time for that register to drain too.  This also prevents subsequent
> messages produced to the console from getting clobbered, owing to what
> seems a transmitter synchronisation issue.
>
> When called from sbd_serial_console_init() it is too early for fsleep()
> to work and even before lpj has been calculated and therefore the delay
> is actually not sufficient for the transmitter to drain and is merely a
> placeholder now.  This will be addressed in a follow-up change.
>
> Fixes: 84a9582fd203 ("serial: core: Start managing serial controllers to enable runtime PM")
> Signed-off-by: Maciej W. Rozycki <macro@xxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx # v6.5+
> ---
> Changes from v1 (1/4),
> <https://lore.kernel.org/r/alpine.DEB.2.21.2604130321540.29980@xxxxxxxxxxxxxxxxx/>:
>
> - Sanitise the change heading.
> ---
>   drivers/tty/serial/sb1250-duart.c |   22 ++++++++++++++++++++++
>   1 file changed, 22 insertions(+)

Reviewed-by: Philippe Mathieu-Daudé <philmd@xxxxxxxxxxxxxxxx>