linux-kernel - Re: [PATCH v5 09/12] clk: actions: Add fixed factor clock support

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Date:   Mon, 19 Mar 2018 18:10:03 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        afaerber@...e.de, mark.rutland@....com, mturquette@...libre.com,
        robh+dt@...nel.org
Cc:     liuwei@...ions-semi.com, mp-cs@...ions-semi.com,
        96boards@...obotics.com, devicetree@...r.kernel.org,
        davem@...emloft.net, mchehab@...nel.org,
        daniel.thompson@...aro.org, amit.kucheria@...aro.org,
        viresh.kumar@...aro.org, hzhang@...obotics.com,
        bdong@...obotics.com, linux-kernel@...r.kernel.org,
        linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        manivannanece23@...il.com,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Subject: Re: [PATCH v5 09/12] clk: actions: Add fixed factor clock support

Quoting Manivannan Sadhasivam (2018-03-17 03:09:49)
> Add support for Actions Semi fixed factor clock together with
> helper functions to be used in composite clock.
> 
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> ---
>  drivers/clk/actions/Makefile           |  1 +
>  drivers/clk/actions/owl-fixed-factor.c | 81 ++++++++++++++++++++++++++++++++++
>  drivers/clk/actions/owl-fixed-factor.h | 62 ++++++++++++++++++++++++++
>  3 files changed, 144 insertions(+)
>  create mode 100644 drivers/clk/actions/owl-fixed-factor.c
>  create mode 100644 drivers/clk/actions/owl-fixed-factor.h
> 
> diff --git a/drivers/clk/actions/Makefile b/drivers/clk/actions/Makefile
> index 994357fa560b..b618696ba54e 100644
> --- a/drivers/clk/actions/Makefile
> +++ b/drivers/clk/actions/Makefile
> @@ -5,3 +5,4 @@ clk-owl-y                       += owl-gate.o
>  clk-owl-y                      += owl-mux.o
>  clk-owl-y                      += owl-divider.o
>  clk-owl-y                      += owl-factor.o
> +clk-owl-y                      += owl-fixed-factor.o
> diff --git a/drivers/clk/actions/owl-fixed-factor.c b/drivers/clk/actions/owl-fixed-factor.c
> new file mode 100644
> index 000000000000..f1281565129c
> --- /dev/null
> +++ b/drivers/clk/actions/owl-fixed-factor.c
> @@ -0,0 +1,81 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +//
> +// OWL fixed factor clock driver
> +//
> +// Copyright (c) 2014 Actions Semi Inc.
> +// Author: David Liu <liuwei@...ions-semi.com>
> +//
> +// Copyright (c) 2018 Linaro Ltd.
> +// Author: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> +
> +#include <linux/clk-provider.h>
> +#include <linux/regmap.h>
> +#include <linux/slab.h>
> +
> +#include "owl-fixed-factor.h"
> +
> +long owl_fix_fact_helper_round_rate(struct owl_clk_common *common,
> +                               const struct owl_fix_fact_hw *fix_fact_hw,
> +                               unsigned long rate,
> +                               unsigned long *parent_rate)
> +{
> +       if (clk_hw_get_flags(&common->hw) & CLK_SET_RATE_PARENT) {
> +               unsigned long best_parent;
> +
> +               best_parent = (rate / fix_fact_hw->mul) * fix_fact_hw->div;
> +               *parent_rate = clk_hw_round_rate(clk_hw_get_parent(&common->hw),
> +                                                       best_parent);
> +       }
> +
> +       return (*parent_rate / fix_fact_hw->div) * fix_fact_hw->mul;
> +}
> +
> +static long owl_fix_fact_round_rate(struct clk_hw *hw, unsigned long rate,
> +                       unsigned long *parent_rate)
> +{
> +       struct owl_fix_fact *fix_fact = hw_to_owl_fix_fact(hw);
> +       struct owl_fix_fact_hw *fix_fact_hw = &fix_fact->fix_fact_hw;
> +
> +       return owl_fix_fact_helper_round_rate(&fix_fact->common, fix_fact_hw,
> +                                                       rate, parent_rate);
> +}
> +
> +unsigned long owl_fix_fact_helper_recalc_rate(struct owl_clk_common *common,
> +                       const struct owl_fix_fact_hw *fix_fact_hw,
> +                       unsigned long parent_rate)
> +{
> +       unsigned long long int rate;
> +
> +       rate = (unsigned long long int)parent_rate * fix_fact_hw->mul;
> +       do_div(rate, fix_fact_hw->div);
> +
> +       return (unsigned long)rate;

You can drop the cast.

> +}
> +
> +static unsigned long owl_fix_fact_recalc_rate(struct clk_hw *hw,
> +                       unsigned long parent_rate)
> +{
> +       struct owl_fix_fact *fix_fact = hw_to_owl_fix_fact(hw);
> +       struct owl_fix_fact_hw *fix_fact_hw = &fix_fact->fix_fact_hw;
> +
> +       return owl_fix_fact_helper_recalc_rate(&fix_fact->common, fix_fact_hw,
> +                                                       parent_rate);
> +}
> +
> +static int owl_fix_fact_set_rate(struct clk_hw *hw, unsigned long rate,
> +                              unsigned long parent_rate)
> +{
> +       /*
> +        * We must report success but we can do so unconditionally because
> +        * clk_fix_fact_round_rate returns values that ensure this call is a

What function is that?

> +        * nop.
> +        */
> +
> +       return 0;
> +}
> +
> +const struct clk_ops owl_fix_fact_ops = {
> +       .round_rate     = owl_fix_fact_round_rate,
> +       .recalc_rate    = owl_fix_fact_recalc_rate,
> +       .set_rate       = owl_fix_fact_set_rate,
> +};

Why can't you use the regular fixed factor clk code and ops?