linux-kernel - Re: [PATCH v3 6/8] clk: sunxi-ng: mux: Support finding closest rate

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Message-ID: <b7gnap57aajkbhbbcbgallvqjdc7nzppjjwnancgmm5ibmhdaq@cftau72qyjdu>
Date:   Mon, 3 Jul 2023 09:38:48 +0200
From:   Maxime Ripard <maxime@...no.tech>
To:     Frank Oltmanns <frank@...manns.dev>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Samuel Holland <samuel@...lland.org>,
        Andre Przywara <andre.przywara@....com>,
        Roman Beranek <me@...y.cz>, linux-clk@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 6/8] clk: sunxi-ng: mux: Support finding closest rate

On Sun, Jul 02, 2023 at 07:55:25PM +0200, Frank Oltmanns wrote:
> When finding the best rate for a mux clock, consider rates that are
> higher than the requested rate by introducing a new clk_ops structure
> that uses the existing __clk_mux_determine_rate_closest function.
> Furthermore introduce an initialization macro that uses this new
> structure.
> 
> Signed-off-by: Frank Oltmanns <frank@...manns.dev>
> ---
>  drivers/clk/sunxi-ng/ccu_mux.c | 13 +++++++++++++
>  drivers/clk/sunxi-ng/ccu_mux.h | 17 +++++++++++++++++
>  2 files changed, 30 insertions(+)
> 
> diff --git a/drivers/clk/sunxi-ng/ccu_mux.c b/drivers/clk/sunxi-ng/ccu_mux.c
> index 8594d6a4addd..49a592bdeacf 100644
> --- a/drivers/clk/sunxi-ng/ccu_mux.c
> +++ b/drivers/clk/sunxi-ng/ccu_mux.c
> @@ -264,6 +264,19 @@ static unsigned long ccu_mux_recalc_rate(struct clk_hw *hw,
>  					   parent_rate);
>  }
>  
> +const struct clk_ops ccu_mux_closest_ops = {
> +	.disable	= ccu_mux_disable,
> +	.enable		= ccu_mux_enable,
> +	.is_enabled	= ccu_mux_is_enabled,
> +
> +	.get_parent	= ccu_mux_get_parent,
> +	.set_parent	= ccu_mux_set_parent,
> +
> +	.determine_rate	= __clk_mux_determine_rate_closest,
> +	.recalc_rate	= ccu_mux_recalc_rate,
> +};
> +EXPORT_SYMBOL_NS_GPL(ccu_mux_closest_ops, SUNXI_CCU);
> +

This is also a bit inconsistent with the other clocks: most (all?) of
them will simply handle this through a flag, but this one requires a new
set of clk_ops as well?

I think we should create our own wrapper here around
__clk_mux_determine_rate and either call
__clk_mux_determine_rate_closest or __clk_mux_determine_rate depending
on the state of the flags, or call __clk_mux_determine_rate_flags with
the proper flags set for our clock.

The former is probably slightly simpler.

>  const struct clk_ops ccu_mux_ops = {
>  	.disable	= ccu_mux_disable,
>  	.enable		= ccu_mux_enable,
> diff --git a/drivers/clk/sunxi-ng/ccu_mux.h b/drivers/clk/sunxi-ng/ccu_mux.h
> index 2c1811a445b0..c4ee14e43719 100644
> --- a/drivers/clk/sunxi-ng/ccu_mux.h
> +++ b/drivers/clk/sunxi-ng/ccu_mux.h
> @@ -46,6 +46,22 @@ struct ccu_mux {
>  	struct ccu_common	common;
>  };
>  
> +#define SUNXI_CCU_MUX_TABLE_WITH_GATE_CLOSEST(_struct, _name, _parents, _table,	\
> +				     _reg, _shift, _width, _gate,	\
> +				     _flags)				\
> +	struct ccu_mux _struct = {					\
> +		.enable	= _gate,					\
> +		.mux	= _SUNXI_CCU_MUX_TABLE(_shift, _width, _table),	\
> +		.common	= {						\
> +			.reg		= _reg,				\
> +			.hw.init	= CLK_HW_INIT_PARENTS(_name,	\
> +							      _parents, \
> +							      &ccu_mux_closest_ops, \
> +							      _flags),	\
> +			.features	= CCU_FEATURE_CLOSEST_RATE,	\
> +		}							\
> +	}
> +

I'm fine with that one, but like we discussed on the NM (I think?) patch
already, this creates some clocks and macros that will use the feature
as a flag, and some will encode it into their name.

Given that we need it here too, I'm really inclined to prefer what you
did there, and thus create a new macro for pll-video0 instead of
modifying the existing one.

Maxime

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