[PATCH v2 2/2] serial: introduce CONFIG_CONSOLE_FLUSH_ON_NEWLINE

[Simon Glass]

On Mon, 16 Oct 2023 at 02:36, Rasmus Villemoes
<rasmus.villemoes at prevas.dk> wrote:
>
> When debugging, one sometimes only gets partial output lines or
> nothing at all from the last printf, because the uart has a largish
> buffer, and the code after the printf() may cause the CPU to hang
> before the uart IP has time to actually emit all the characters. That
> can be very confusing, because one doesn't then know exactly where the
> hang happens.
>
> Introduce a config knob allowing one to wait for the uart fifo to
> drain whenever a newline character is printed, roughly corresponding
> to the effect of setvbuf(..., _IOLBF, ...) in ordinary C programs.
>
> Since this uses IS_ENABLED() instead of cpp ifdef, we can remove the
> ifdef around the _serial_flush() definition - if neither
> CONSOLE_FLUSH_SUPPORT or CONSOLE_FLUSH_ON_NEWLINE are enabled, the
> compiler elides _serial_flush(), but it won't warn about it being
> unused.
>
> Signed-off-by: Rasmus Villemoes <rasmus.villemoes at prevas.dk>
> ---
>  common/Kconfig                 | 10 ++++++++++
>  drivers/serial/serial-uclass.c |  8 ++++++--
>  2 files changed, 16 insertions(+), 2 deletions(-)

Reviewed-by: Simon Glass <sjg at chromium.org>