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

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Message-ID: <ryramlegltk3dayye2cy73s4el7wx5ye7o2okd5oboefrb6lrh@p7bzr2fohqa3>
Date:   Mon, 3 Jul 2023 13:37:15 +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 Mon, Jul 03, 2023 at 11:17:24AM +0200, Frank Oltmanns wrote:
> 
> On 2023-07-03 at 09:38:48 +0200, Maxime Ripard <maxime@...no.tech> wrote:
> > [[PGP Signed Part:Undecided]]
> > 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.
> 
> Ok, I will address that in v4.
> 
> >
> >>  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.
> 
> Ok. Just to be clear: What I did in this patch is fine and I should use
> the same approach for NM. Did I get that right?

Yes. Leave the NM macro as it is, and add a new _CLOSEST variant that
sets the flag like you did there.

Maxime

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