linux-kernel - Re: [PATCH] clk: mediatek: Fix -Wunused-const-variable

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Date:   Thu, 27 Jun 2019 16:07:05 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     fparent@...libre.com, sboyd@...nel.org
Cc:     mturquette@...libre.com, Nathan Huckleberry <nhuck@...gle.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        linux-clk@...r.kernel.org,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-mediatek@...ts.infradead.org,
        LKML <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Arnd Bergmann <arnd@...db.de>, Mark Brown <broonie@...aro.org>
Subject: Re: [PATCH] clk: mediatek: Fix -Wunused-const-variable

On Thu, Jun 27, 2019 at 3:15 PM 'Nathan Huckleberry' via Clang Built
Linux <clang-built-linux@...glegroups.com> wrote:
>
> Clang produces the following warning
>
> drivers/clk/mediatek/clk-mt8516.c:234:27: warning: unused variable
> 'ddrphycfg_parents' [-Wunused-const-variable] static const char * const
> ddrphycfg_parents[] __initconst = {
>
> This variable has never been used. Deleting it to cleanup the warning.

comparing this to `nfi1x_pad_parents`, it looks like this maybe should
be an entry in `top_muxes`, but there seem to be some magic constants
in those that I don't understand or know what we'd use for
`ddrphycfg_parents`.

Again, looking at `nfi1x_pad_parents` for reference, we see
`CLK_TOP_NFI1X_PAD_SEL` used with it and being defined in the device
tree bindings in include/dt-bindings/clock/mt8516-clk.h.  I would
guess that `CLK_TOP_DDRPHYCFG_SEL` should be used in `top_muxes` with
`ddrphycfg_parents`.

`CLK_TOP_DDRPHYCFG_SEL` appears in:
drivers/clk/mediatek/clk-mt8135.c
drivers/clk/mediatek/clk-mt8173.c
drivers/clk/mediatek/clk-mt2701.c
drivers/clk/mediatek/clk-mt7629.c
drivers/clk/mediatek/clk-mt7622.c
but not the translation unit in question:
drivers/clk/mediatek/clk-mt8516.c

in most of the above (except clk-mt2701.c which simply has 1
additional field but otherwise matching values, and clk-mt8135.c which
has 2 different values), it's added to a similarly named and typed
`top_muxes` as:

MUX_GATE(CLK_TOP_DDRPHYCFG_SEL, "ddrphycfg_sel", ddrphycfg_parents,
  0x040, 16, 1, 23),

even then `ddrphycfg_parents` shows up in the other translation units
in the same statement as `CLK_TOP_DDRPHYCFG_SEL`.

So questions to the maintainers I have:
1. Is the above `MUX_GATE` what should be added to `top_muxes` in
drivers/clk/mediatek/clk-mt8516.c?
2. If so, where? Is order of the array elements important.

If the answer to 1 is no, then we should take Nathan's patch.

>
> Cc: clang-built-linux@...glegroups.com
> Link: https://github.com/ClangBuiltLinux/linux/issues/523
> Signed-off-by: Nathan Huckleberry <nhuck@...gle.com>
> ---
>  drivers/clk/mediatek/clk-mt8516.c | 5 -----
>  1 file changed, 5 deletions(-)
>
> diff --git a/drivers/clk/mediatek/clk-mt8516.c b/drivers/clk/mediatek/clk-mt8516.c
> index 26fe43cc9ea2..9d4261ecc760 100644
> --- a/drivers/clk/mediatek/clk-mt8516.c
> +++ b/drivers/clk/mediatek/clk-mt8516.c
> @@ -231,11 +231,6 @@ static const char * const nfi1x_pad_parents[] __initconst = {
>         "nfi1x_ck"
>  };
>
> -static const char * const ddrphycfg_parents[] __initconst = {
> -       "clk26m_ck",
> -       "mainpll_d16"
> -};
> -


-- 
Thanks,
~Nick Desaulniers