linux-kernel - Re: [PATCH v1 1/4] clk: samsung: change COMMON_CLK

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Date:   Tue, 21 Sep 2021 09:50:57 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Krzysztof Kozlowski <krzk@...nel.org>
Cc:     Will McVicker <willmcvicker@...gle.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Sylwester Nawrocki <s.nawrocki@...sung.com>,
        Tomasz Figa <tomasz.figa@...il.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Lee Jones <lee.jones@...aro.org>,
        Android Kernel Team <kernel-team@...roid.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
        linux-clk <linux-clk@...r.kernel.org>
Subject: Re: [PATCH v1 1/4] clk: samsung: change COMMON_CLK_SAMSUNG default
 config logic

On Tue, Sep 21, 2021 at 9:31 AM Krzysztof Kozlowski <krzk@...nel.org> wrote:
> On 20/09/2021 21:03, Will McVicker wrote:
> > COMMON_CLK_SAMSUNG is selected by ARCH_EXYNOS which forces this config
> > to be built-in when ARCH_EXYNOS is enabled. Switch the logic to use a
> > "default y if ARCH_EXYNOS" to provide flexibilty for vendors to disable
> > or modularize this driver.
>
> The clock drivers are essential, you cannot disable them for a generic
> kernel supporting ARCH_EXYNOS. Such kernel won't work properly on platforms.

Obviously it's not gonna work if the clock driver is not enabled
at all.  But does it work if you make the clock driver modular, and
put it with all other essential driver modules in initramfs?  Debugging
would be hard, as the serial console driver also relies on clocks
and PM Domains etc.

If not, this patch should be NAKed, until it works with a modular
clock driver.

If yes, perhaps another line should be added (_before_ the other line)?

  + default m if ARCH_EXYNOS && MODULES
    default y if ARCH_EXYNOS

However, many developers may want MODULES=y, but not want to bother
with an initramfs.  So perhaps we need a new symbol
MINIMUM_GENERIC_KERNEL or so, protected by EXPERT, and make the
driver default to m if that is enabled?

Gr{oetje,eeting}s,

                        Geert

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