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

[Geert Uytterhoeven <geert@linux-m68k.org>]

Hi Olof,

On Mon, Nov 21, 2016 at 5:35 PM, Olof Johansson <olof@lixom.net> wrote:
> On Mon, Nov 21, 2016 at 8:27 AM, Geert Uytterhoeven
> <geert@linux-m68k.org> wrote:
>> On Mon, Nov 21, 2016 at 5:19 PM, Olof Johansson <olof@lixom.net> wrote:
>>> On Mon, Nov 21, 2016 at 1:31 AM, Geert Uytterhoeven
>>> <geert@linux-m68k.org> wrote:
>>>> On Sat, Nov 19, 2016 at 2:28 AM, Olof Johansson <olof@lixom.net> wrote:
>>>>> On Thu, Nov 17, 2016 at 02:34:25PM +0100, Simon Horman wrote:
>>>>>> Please consider these second round of Renesas ARM based SoC updates for v4.10.
>>>>
>>>>>> * Basic support for r8a7745 SoC
>>>>>>
>>>>>> ----------------------------------------------------------------
>>>>>> Sergei Shtylyov (2):
>>>>>>       ARM: shmobile: r8a7745: basic SoC support
>>>>>>       ARM: shmobile: document SK-RZG1E board
>>>>>
>>>>> 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?

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.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@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