[U-Boot] [PATCH v2 21/44] Convert CONFIG_SPL_GPIO_SUPPORT to Kconfig

[Simon Glass]

Hi,

On 6 September 2016 at 09:54, Tom Rini <trini at konsulko.com> wrote:
> On Mon, Sep 05, 2016 at 07:04:45PM -0600, Simon Glass wrote:
>> Hi Masahiro,
>>
>> On 4 September 2016 at 20:40, Masahiro Yamada
>> <yamada.masahiro at socionext.com> wrote:
>> > 2016-09-02 23:35 GMT+09:00 Tom Rini <trini at konsulko.com>:
>> >
>> >>> >> diff --git a/arch/arm/mach-exynos/Kconfig b/arch/arm/mach-exynos/Kconfig
>> >>> >> index c25fcf3..d4a5bc9 100644
>> >>> >> --- a/arch/arm/mach-exynos/Kconfig
>> >>> >> +++ b/arch/arm/mach-exynos/Kconfig
>> >>> >> @@ -61,6 +61,9 @@ endif
>> >>> >>
>> >>> >>  if ARCH_EXYNOS5
>> >>> >>
>> >>> >> +config SPL_GPIO_SUPPORT
>> >>> >> +       default y
>> >>> >> +
>> >>> >
>> >>> >
>> >>> > As we discussed before,
>> >>> > we decided to not do this.
>> >>>
>> >>> Tom was keen to avoid changing every defconfig file. It is there
>> >>> another way to express common defaults?
>> >>
>> >> I was thinking in the Kconfig with the entry for SPL_GPIO_SUPPORT, for
>> >> optional stuff and select in the board, etc, Kconfig for non-optional
>> >> stuff.  Now, I realize that optional vs non-optional is more the domain
>> >> of the individual SoC custodians, so we'll have some clean up afterwards
>> >> that isn't on you (well, aside from the SoCs you know like rockchip ;)).
>> >
>> > config SPL_GPIO_SUPPORT
>> >        default y
>> >
>> > is incorrect because it could violate
>> > the dependency in the proper Kconfig entry in spl/Kconfig.
>>
>> But only if options depended on by this are not set, right?
>>
>> >
>> >
>> >
>> >
>> > Basically, we are supposed to use "select FOO" when it is mandatory,
>> > or add CONFIG_FOO=y in a defconfig when the board wants it, but
>> > can still make it optional.
>>
>> Yes, but this is not mandatory. It is a default, and some boards will
>> unset it. I did this in response to Tom's comment about trying to cut
>> down the defconfig patch size.
>
> Well, here is where it is tricky.  For example, in SPL when we bring in
> the GPIO code, it's because it's required to enable DDR or know which
> board rev we're on.  So it needs to be select'd or people will get
> failure to build problems.  Other things like filesystems should be an
> option.
>
>> > I know our pain comes from that "include" is not supported by Kconfig.
>>
>> How would that help? Why don't we implement it?
>
> Well, if we could more literally translate the various *common*.h files
> into a Kconfig file that was "included" it would be easier to say that
> various CONFIG variables are just a bool (or hex) and then
> board/ti/am335x/Kconfig would 'include
> include/kconfig/ti_am33xx_common.k' and get all of the stuff it
> used to get from include/configs/ti_am335x_common.h.
>
>> > What I can suggest now is:
>> >
>> >
>> >
>> > [1]  Add ARCH_WANT_* to specify a SoC-common default.
>> >
>> >
>> >        config SPL_GPIO_SUPPORT
>> >                 bool "GPIO support for SPL"
>> >                 default  ARCH_WANT_SPL_GPIO_SUPPORT
>> >
>> >
>> >        config ARCH_WANT_SPL_GPIO_SUPPORT
>> >                 bool
>> >
>> >
>> >        config ARCH_EXYNOS5
>> >                select ARCH_WANT_SPL_GPIO_SUPPORT
>> >
>> >
>> > Linux used to have ARCH_WANT_OPTIONAL_GPIOLIB to do similar things.
>> > (they stopped this way, though)
>
> This may be better.
>
>> > [2] Support multi boards with one defconfig
>> >     (barebox supports multi-platform like Linux does.)
>
> Unless I missed something, this is just kicking the problem up a level
> frankly.  They just allow (and we could / can / do, depending on the
> SoC) one full "barebox" to be loaded by the board-specific preloader.
> We can, should, and hopefully will once DM is 'done', have this be an
> option.  But that's a different problem set from how do we configure the
> board specific part of a build.
>
>> > [3] use pre-processor to support #include <...>
>> >
>> >
>> >
>> >
>> >
>> > BTW, SPL_GPIO_SUPPORT is optional in this case?
>> >
>> > U-Boot proper supports a command line interface,
>> > while SPL is usually run in a non-interactive mode.
>> >
>> > So, what SPL needs is generally mandatory,
>> > so we can "select" it,  I guess.
>>
>> I found a lot of cases where 90% of the boards with the same SoC  had
>> the same setting for this (and a few other) options, but some boards
>> did not. So I did not want to use select, since then it is impossible
>> to unselect.
>
> Maybe this is where [1] above will work best and we can select
> ARCH_WANT_.. (or BOARD_WANT_...) from TARGET_... and leave some things
> as questions.
>
>> This series is actually really tricky. I'm looking forward to putting
>> it to bed. We need to make these conversions easier.
>
> Agreed!

I am not sure about the WANT business, but I am sure that I don't want
to work through all the SoCs and figure how how they should set it.
I'd like to get this series in since i think it is a good starting
point for improving things. Changing to WANT will be easier after that
if we want to. Also I feel this should be the job of SoC maintainers.

Regards,
Simon