linux-kernel - Re: [PATCH 6/7] clk: scmi: Allocate CLK operations dynamically

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Date: Wed, 21 Feb 2024 21:44:14 -0800
From: Stephen Boyd <sboyd@...nel.org>
To: Cristian Marussi <cristian.marussi@....com>, linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc: sudeep.holla@....com, james.quinlan@...adcom.com, f.fainelli@...il.com, vincent.guittot@...aro.org, peng.fan@....nxp.com, michal.simek@....com, quic_sibis@...cinc.com, quic_nkela@...cinc.com, souvik.chakravarty@....com, Cristian Marussi <cristian.marussi@....com>, Michael Turquette <mturquette@...libre.com>, linux-clk@...r.kernel.org
Subject: Re: [PATCH 6/7] clk: scmi: Allocate CLK operations dynamically

Quoting Cristian Marussi (2024-02-14 10:30:05)
> diff --git a/drivers/clk/clk-scmi.c b/drivers/clk/clk-scmi.c
> index 5747b6d651f0..b91a0dbd2fe0 100644
> --- a/drivers/clk/clk-scmi.c
> +++ b/drivers/clk/clk-scmi.c
> @@ -158,51 +158,6 @@ static int scmi_clk_atomic_is_enabled(struct clk_hw *hw)
>         return !!enabled;
>  }
>  
> -/*
> - * We can provide enable/disable/is_enabled atomic callbacks only if the
> - * underlying SCMI transport for an SCMI instance is configured to handle
> - * SCMI commands in an atomic manner.
> - *
> - * When no SCMI atomic transport support is available we instead provide only
> - * the prepare/unprepare API, as allowed by the clock framework when atomic
> - * calls are not available.
> - *
> - * Two distinct sets of clk_ops are provided since we could have multiple SCMI
> - * instances with different underlying transport quality, so they cannot be
> - * shared.
> - */
> -static const struct clk_ops scmi_clk_ops = {
> -       .recalc_rate = scmi_clk_recalc_rate,
> -       .round_rate = scmi_clk_round_rate,
> -       .set_rate = scmi_clk_set_rate,
> -       .prepare = scmi_clk_enable,
> -       .unprepare = scmi_clk_disable,
> -       .set_parent = scmi_clk_set_parent,
> -       .get_parent = scmi_clk_get_parent,
> -       .determine_rate = scmi_clk_determine_rate,
> -};
> -
> -static const struct clk_ops scmi_atomic_clk_ops = {

It's not great to move these function pointer structs out of RO memory
to RW. I'm also not convinced that it's any better to construct them at
runtime. Isn't there a constant set of possible clk configurations? Or
why can't we simply add some failures to the clk_ops functions instead?

> -       .recalc_rate = scmi_clk_recalc_rate,
> -       .round_rate = scmi_clk_round_rate,
> -       .set_rate = scmi_clk_set_rate,
> -       .enable = scmi_clk_atomic_enable,
> -       .disable = scmi_clk_atomic_disable,
> -       .is_enabled = scmi_clk_atomic_is_enabled,