[U-Boot] [PATCH 17/19] serial: Support an early UART for debugging

[Masahiro Yamada]

Hi Simon,



On Mon, 15 Dec 2014 07:19:52 -0700
Simon Glass <sjg at chromium.org> wrote:

> 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

Assembler can guarantee that stack is not used.


> - it doesn't need to be ARM-specific

OK.

> 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,

OK.

> and it is possible for
> it to operate without a stack on some architectures (e.g. PowerPC, ARM).

It depends on the optimization option -O2 / -Os.

In 18/19, you add "static inline" to calc_divisor().

"static inline" does not force-inline the code,
but still leaves it to the compiler decision.
(Marek Vasut also mentioned this in commit 4425e62856)





Best Regards
Masahiro Yamada