[coreboot] [RFC] Removing RTC configurable baud rate

[Nico Huber]

On 12.05.2017 21:59, Arthur Heymans wrote:
> Hi
> 
> In the latest CCM[1] the question was raised whether someone still uses
> the configuration option baud_rate from RTC nvram (CMOS) and if not
> maybe think about removing this.
> 
> The issues raised with this code were:
> * they are an extra burden to maintain since console init is done over
> multiple stages and needs different code paths over ROMCC and GCC;
> * Its not buildtested so easy to miss breakages;
> * Many boards don't have an cmos.defaults so it often ends up at weird
> settings.
> 
> Granted many of these issues need separate fixing anyway: we need
> cmos.default on each board that has cmos.layout, default Kconfig options
> could be changed to build test this.

Are there any objections to enable USE_OPTION_TABLE by default if a
cmos.default is available? That way we would spare us the hassle to
maintain additional configs for build tests.

> 
> So the question is: is someone still using the possibility to configure
> uart baud rates from rtc nvram. (Keep in mind that is still possible to
> set the default baud rate from Kconfig options)

That we have two places to configure it, also creates confusion. Espe-
cially because the Kconfig option is more visible but the NVRAM option
overrides it. A good way to fix this would be to patch the cmos.default
with the Kconfig choice. Even if we decide to remove `baud_rate` there
are still other options (at least `debug_level`) that suffer from the
same problem.

Nico

> 
> I already created a RFC patch that removes it:
> https://review.coreboot.org/#/c/19682/
> 
> [1] https://mail.coreboot.org/pipermail/coreboot/2017-May/084266.html
> CCM report
> 
> 
> Kind regards
> ------------
> 
> Arthur
>