[GIT PULL] Second Round of Renesas ARM Based SoC Updates for v4.10

[Geert Uytterhoeven]

Hi Olof,

On Wed, Nov 23, 2016 at 12:30 AM, Olof Johansson <olof at lixom.net> wrote:
> On Tue, Nov 22, 2016 at 1:56 AM, Geert Uytterhoeven
> <geert at linux-m68k.org> wrote:
>> On Mon, Nov 21, 2016 at 5:35 PM, Olof Johansson <olof at lixom.net> wrote:
>>> On Mon, Nov 21, 2016 at 8:27 AM, Geert Uytterhoeven
>>> <geert at linux-m68k.org> wrote:
>>>> On Mon, Nov 21, 2016 at 5:19 PM, Olof Johansson <olof at lixom.net> wrote:
>>>>> On Mon, Nov 21, 2016 at 1:31 AM, Geert Uytterhoeven
>>>>> <geert at linux-m68k.org> wrote:
>>>>>> On Sat, Nov 19, 2016 at 2:28 AM, Olof Johansson <olof at lixom.net> wrote:
>>>>>>> Is there a reason you're adding a config option per SoC?
>>>>>>>
>>>>>>> I think you'd be better off not adding these config options, and just adding
>>>>>>> support for the SoCs through compatibles (and adding the drivers to defconfigs,
>>>>>>> etc).
>>>>>>
>>>>>> Yes there is a reason: kernel size.
>>>>>> The main offenders are the pinctrl tables, which add ca. 20-50 KiB per
>>>>>> supported SoC.
>>>>>
>>>>> So don't turn on that pinctrl driver unless you have that SoC?
>>>>
>>>> The enablement of the pinctrl driver (and the clock driver, FWIW) is controlled
>>>> by the SoC Kconfig symbol. If you want support for the SoC, you want the
>>>> pinctrl driver, too.
>>>
>>> Oh, that's trivial to fix! Do as almost all other SoCs do, and don't
>>> use silent options.
>>
>> What does that gain us? The ability to enable support for an SoC, without
>> enabling the accompanying pinctrl driver, leading to a non-booting system?
>
> It doesn't enable anything new, it just makes it less awkward for you
> to add new SoCs in the future without creating dependencies on new
> Kconfig symbols in the arch directory.
>
>> As soon as you have any pinctrl properties in the DT, you need the pinctrl
>> driver. Unless you disable CONFIG_PINCTRL (it's selected, and not
>> user-controlled), and rely on fragile reset state/boot loader.
>>
>> Pinctrl (and clock and irqchip) on-SoC drivers are special: if you fail to
>> include them, the system won't boot.
>
> This isn't about booting without a pinctrl driver. It's about avoiding
> adding new config symbols when they're not needed.
>
> I started out comparing your way of using config options with, for
> example, Exynos that has a bunch of different SoCs enabled. Having
> dependencies described clearly has some value, since it can be hard to
> know if you can turn off a driver and still have a bootable system
> with some of the other platforms.
>
> That being said, I think you should look at changing how you use your
> config options to make it less messy to add new ones:

[...]

Thanks, I'll have a look to see if we can improve things...

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds