linux-kernel - Re: [PATCH] clk: meson: meson8b: Simplify notifier clock lookup

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Date:   Tue, 08 Aug 2023 15:21:46 +0200
From:   Jerome Brunet <jbrunet@...libre.com>
To:     Chen-Yu Tsai <wenst@...omium.org>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Kevin Hilman <khilman@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Stephen Boyd <sboyd@...nel.org>
Cc:     linux-amlogic@...ts.infradead.org, linux-clk@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] clk: meson: meson8b: Simplify notifier clock lookup


On Mon 31 Jul 2023 at 12:27, Chen-Yu Tsai <wenst@...omium.org> wrote:

> The driver registers a clock notifier by first getting the name of one
> of its clocks it just registered, then uses the name to look up the
> clock. The lookup is not needed, since each clock provider already
> has a clock attached to it. Use that instead to get rid of a
> __clk_lookup() call.
>
> Signed-off-by: Chen-Yu Tsai <wenst@...omium.org>
> ---
> Found this could be simplified while looking through some clk core code.
>
>
>  drivers/clk/meson/meson8b.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
>
> diff --git a/drivers/clk/meson/meson8b.c b/drivers/clk/meson/meson8b.c
> index 827e78fb16a8..c4336ac012bf 100644
> --- a/drivers/clk/meson/meson8b.c
> +++ b/drivers/clk/meson/meson8b.c
> @@ -3793,7 +3793,6 @@ static void __init meson8b_clkc_init_common(struct device_node *np,
>  {
>  	struct meson8b_clk_reset *rstc;
>  	struct device_node *parent_np;
> -	const char *notifier_clk_name;
>  	struct clk *notifier_clk;
>  	struct regmap *map;
>  	int i, ret;
> @@ -3847,9 +3846,7 @@ static void __init meson8b_clkc_init_common(struct device_node *np,
>  	 * tricky programming sequence will be handled by the forthcoming
>  	 * coordinated clock rates mechanism once that feature is released.
>  	 */
> -	notifier_clk_name = clk_hw_get_name(&meson8b_cpu_scale_out_sel.hw);
> -	notifier_clk = __clk_lookup(notifier_clk_name);
> -	ret = clk_notifier_register(notifier_clk, &meson8b_cpu_nb_data.nb);
> +	ret = clk_notifier_register(meson8b_cpu_scale_out_sel.hw.clk, &meson8b_cpu_nb_data.nb);

Hi Chen-Yu,

Your patch seems valid, as CCF stands right now.

However, I believe there is a will to drop the 'struct clk' instance that
automatically gets created with each 'struct clk_hw'. This change would
not help going in this direction

Stephen, what do you think ? 

>  	if (ret) {
>  		pr_err("%s: failed to register the CPU clock notifier\n",
>  		       __func__);