The serial output from the debug UART carries on going far to the
right in the console.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Stefan Roese <sr@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>

It is useful to see a message from the debug UART early during boot so that
you know things are working. Add an option to enable this. The message will
be displayed as soon as debug_uart_init() is called.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

Some boards need to set things up before the debug UART can be used. On
these boards a call to debug_uart_init() is insufficient. When this option
is enabled, the function board_debug_uart_init() will be called when
debug_uart_init() is called. You can put any code here that is needed to
set up the UART ready for use, such as set pin multiplexing or enable
clocks.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

We want to be able to add other common code to this function. So change the
driver's version to have an underscore before it, just like
_debug_uart_putc(). Define debug_uart_init() to call this version.

Update all drivers to this new method.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

This does not actually help any current arch. For x86 it makes it harder
to call (requires stack) and for ARM it has no effect. Drop it.

Signed-off-by: Simon Glass <sjg@chromium.org>

This came up in a discussion on the mailing list here:

https://patchwork.ozlabs.org/patch/384613/

My concerns at the time were:
- it doesn't need to be written in assembler
- it doesn't need to be ARM-specific

This patch provides a possible alternative. It works by allowing any serial
driver to export one init function and provide a putc() function. These
can be used to output debug data before the real serial driver is available.

This implementation does not depend on driver model, and it is possible for
it to operate without a stack on some architectures (e.g. PowerPC, ARM). It
provides the same features as the ARM-specific debug.S but with more UART
and architecture support.

Signed-off-by: Simon Glass <sjg@chromium.org>