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

[Masahiro Yamada]

Hi Simon,


2016-09-12 13:16 GMT+09:00 Simon Glass <sjg at chromium.org>:
> 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.


OK, I agree.


But, you added

config SPL_GPIO_SUPPORT
      default y

for some platforms, so it looks like you already figured out
how the default should be set for them.


Anyway, I know this task is too much burden.
How about moving CONFIG_SPL_GPIO_SUPPORT=y to defconfigs verbatim for now?


If SoC maintainers are unhappy about duplicated CONFIG defines in
their defconfigs,
they can work on the WANT refactoring later.



-- 
Best Regards
Masahiro Yamada