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SubjectRe: [PATCH] clk: fix clk_calc_subtree compute duplications
On Fri, Aug 31, 2018 at 2:20 PM Derek Basehore <dbasehore@chromium.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 is fixed by adding a non-recursive function called at every
> step in clk_calc_new_rates that fills in new_rate, new_parent, etc.
> Since the clks not called directly for clk_calc_new_rates can only
> change their rate, we only set new_rate in clk_calc_subtree.
> clk_calc_subtree is also only called on the top clk after it's found
> via clk_calc_new_rates to remove the duplicate recursive calls.
>
> Signed-off-by: Derek Basehore <dbasehore@chromium.org>
> ---
> drivers/clk/clk.c | 20 ++++++++++++--------
> 1 file changed, 12 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index d31055ae6ec6..52032fb1a8a2 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -1609,11 +1609,18 @@ 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, unsigned long new_rate)
> {
> struct clk_core *child;
>
> + core->new_rate = new_rate;
> + hlist_for_each_entry(child, &core->children, child_node)
> + clk_calc_subtree(child, clk_recalc(child, new_rate));
> +}
> +
> +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;
> @@ -1621,11 +1628,6 @@ 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);
> - }
> }
>
> /*
> @@ -1709,7 +1711,7 @@ static struct clk_core *clk_calc_new_rates(struct clk_core *core,
> top = clk_calc_new_rates(parent, best_parent_rate);
>
> out:
> - clk_calc_subtree(core, new_rate, parent, p_index);
> + clk_set_change(core, new_rate, parent, p_index);
>
> return top;
> }
> @@ -1910,6 +1912,8 @@ static int clk_core_set_rate_nolock(struct clk_core *core,
> if (ret)
> return ret;
>
> + clk_calc_subtree(top, top->new_rate);
> +

Oops. This is wrong. Calling here will overwrite new rate settings
such as when determine_rate/round_rate return something different than
clk_recalc(core, parent_rate). I'm working on a larger patch series
where this will be fixed.

> /* notify that we are about to change rates */
> fail_clk = clk_propagate_rate_change(top, PRE_RATE_CHANGE);
> if (fail_clk) {
> --
> 2.19.0.rc1.350.ge57e33dbd1-goog
>

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