linux-kernel - Re: [PATCH 2/6] clk: fix clk_calc

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Date:   Wed, 31 Oct 2018 19:58:31 -0700
From:   "dbasehore ." <dbasehore@...omium.org>
To:     linux-kernel <linux-kernel@...r.kernel.org>
Cc:     linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org, linux-doc@...r.kernel.org,
        sboyd@...nel.org, Michael Turquette <mturquette@...libre.com>,
        Heiko Stübner <heiko@...ech.de>,
        aisheng.dong@....com, mchehab+samsung@...nel.org,
        Jonathan Corbet <corbet@....net>
Subject: Re: [PATCH 2/6] clk: fix clk_calc_subtree compute duplications

On Tue, Oct 23, 2018 at 6:31 PM Derek Basehore <dbasehore@...omium.org> wrote:
>
> clk_calc_subtree was called at every step up the clk tree in
> clk_calc_new_rates. Since it recursively calls itself for its
> children, this means it would be called once on each clk for each
> step above the top clk is.
>
> This fixes this by breaking the subtree calculation into two parts.
> The first part recalcs the rate for each child of the parent clk in
> clk_calc_new_rates. This part is not recursive itself. The second part
> recursively calls a new clk_calc_subtree on the clk_core that was
> passed into clk_set_rate.
>
> Signed-off-by: Derek Basehore <dbasehore@...omium.org>
> ---
>  drivers/clk/clk.c | 30 ++++++++++++++++++++----------
>  1 file changed, 20 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index 95d818f5edb2..61de8ad3e4cf 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -1717,11 +1717,19 @@ static int __clk_speculate_rates(struct clk_core *core,
>         return ret;
>  }
>
> -static void clk_calc_subtree(struct clk_core *core, unsigned long new_rate,
> -                            struct clk_core *new_parent, u8 p_index)
> +static void clk_calc_subtree(struct clk_core *core)
>  {
>         struct clk_core *child;
>
> +       hlist_for_each_entry(child, &core->children, child_node) {
> +               child->new_rate = clk_recalc(child, core->new_rate);
> +               clk_calc_subtree(child);
> +       }
> +}
> +
> +static void clk_set_change(struct clk_core *core, unsigned long new_rate,
> +                          struct clk_core *new_parent, u8 p_index)
> +{
>         core->new_rate = new_rate;
>         core->new_parent = new_parent;
>         core->new_parent_index = p_index;
> @@ -1729,11 +1737,6 @@ static void clk_calc_subtree(struct clk_core *core, unsigned long new_rate,
>         core->new_child = NULL;
>         if (new_parent && new_parent != core->parent)
>                 new_parent->new_child = core;
> -
> -       hlist_for_each_entry(child, &core->children, child_node) {
> -               child->new_rate = clk_recalc(child, new_rate);
> -               clk_calc_subtree(child, child->new_rate, NULL, 0);
> -       }
>  }
>
>  /*
> @@ -1744,7 +1747,7 @@ static struct clk_core *clk_calc_new_rates(struct clk_core *core,
>                                            unsigned long rate)
>  {
>         struct clk_core *top = core;
> -       struct clk_core *old_parent, *parent;
> +       struct clk_core *old_parent, *parent, *child;
>         unsigned long best_parent_rate = 0;
>         unsigned long new_rate;
>         unsigned long min_rate;
> @@ -1791,6 +1794,8 @@ static struct clk_core *clk_calc_new_rates(struct clk_core *core,
>                 /* pass-through clock with adjustable parent */
>                 top = clk_calc_new_rates(parent, rate);
>                 new_rate = parent->new_rate;
> +               hlist_for_each_entry(child, &parent->children, child_node)
> +                       child->new_rate = clk_recalc(child, new_rate);
>                 goto out;
>         }
>
> @@ -1813,11 +1818,14 @@ static struct clk_core *clk_calc_new_rates(struct clk_core *core,
>         }
>
>         if ((core->flags & CLK_SET_RATE_PARENT) && parent &&
> -           best_parent_rate != parent->rate)
> +           best_parent_rate != parent->rate) {
>                 top = clk_calc_new_rates(parent, best_parent_rate);
> +               hlist_for_each_entry(child, &parent->children, child_node)
> +                       child->new_rate = clk_recalc(child, parent->new_rate);
> +       }
>
>  out:
> -       clk_calc_subtree(core, new_rate, parent, p_index);
> +       clk_set_change(core, new_rate, parent, p_index);
>
>         return top;
>  }
> @@ -2018,6 +2026,8 @@ static int clk_core_set_rate_nolock(struct clk_core *core,
>         if (ret)
>                 return ret;
>
> +       clk_calc_subtree(core);

This should be:
hlist_for_each_entry(child, core->new_parent? core->new_parent :
core->parent, child_node)
  clk_calc_subtree(child);

> +
>         /* notify that we are about to change rates */
>         fail_clk = clk_propagate_rate_change(top, PRE_RATE_CHANGE);
>         if (fail_clk) {
> --
> 2.19.1.568.g152ad8e336-goog
>