Re: [PATCH] clk: walk orphan list on clock provider registration

[Stephen Boyd <sboyd@kernel.org>]

Quoting Jerome Brunet (2019-11-29 08:16:58)
> So far, we walked the orphan list every time a new clock was registered
> in CCF. This was fine since the clocks were only referenced by name.
> 
> Now that the clock can be referenced through DT, it is not enough:
> * Controller A register first a reference clocks from controller B
>   through DT.
> * Controller B register all its clocks then register the provider.
> 
> Each time controller B registers a new clock, the orphan list is walked
> but it can't match since the provider is registered yet. When the
> provider is finally registered, the orphan list is not walked unless
> another clock is registered afterward.
> 
> This can lead to situation where some clocks remain orphaned even if
> the parent is available.
> 
> Walking the orphan list on provider registration solves the problem.
> 
> Fixes: fc0c209c147f ("clk: Allow parents to be specified without string names")
> Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
> ---

Sounds right. Thanks for making the fix!

I suspect there should be a reported-by tag though?

>  drivers/clk/clk.c | 59 +++++++++++++++++++++++++++++------------------
>  1 file changed, 37 insertions(+), 22 deletions(-)
> 
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index ef4416721777..917ba37c3b9d 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -3249,6 +3249,34 @@ static inline void clk_debug_unregister(struct clk_core *core)
>  }
>  #endif
>  
> +static void __clk_core_reparent_orphan(void)

Maybe drop the double underscore. clk_core prefix already means "private
to this file".

> +{
> +       struct clk_core *orphan;
> +       struct hlist_node *tmp2;
> +
> +       /*
> +        * walk the list of orphan clocks and reparent any that newly finds a
> +        * parent.
> +        */
> +       hlist_for_each_entry_safe(orphan, tmp2, &clk_orphan_list, child_node) {
> +               struct clk_core *parent = __clk_init_parent(orphan);
> +
> +               /*
> +                * We need to use __clk_set_parent_before() and _after() to
> +                * to properly migrate any prepare/enable count of the orphan
> +                * clock. This is important for CLK_IS_CRITICAL clocks, which
> +                * are enabled during init but might not have a parent yet.
> +                */
> +               if (parent) {
> +                       /* update the clk tree topology */
> +                       __clk_set_parent_before(orphan, parent);
> +                       __clk_set_parent_after(orphan, parent, NULL);
> +                       __clk_recalc_accuracies(orphan);
> +                       __clk_recalc_rates(orphan, 0);
> +               }
> +       }
> +}
> +
>  /**
>   * __clk_core_init - initialize the data structures in a struct clk_core
>   * @core:      clk_core being initialized
> @@ -3259,8 +3287,6 @@ static inline void clk_debug_unregister(struct clk_core *core)
>  static int __clk_core_init(struct clk_core *core)
>  {
>         int ret;
> -       struct clk_core *orphan;
> -       struct hlist_node *tmp2;
>         unsigned long rate;
>  
>         if (!core)
> @@ -3416,27 +3442,8 @@ static int __clk_core_init(struct clk_core *core)
>                 clk_enable_unlock(flags);
>         }
>  
> -       /*
> -        * walk the list of orphan clocks and reparent any that newly finds a
> -        * parent.
> -        */
> -       hlist_for_each_entry_safe(orphan, tmp2, &clk_orphan_list, child_node) {
> -               struct clk_core *parent = __clk_init_parent(orphan);
> +       __clk_core_reparent_orphan();
>  
> -               /*
> -                * We need to use __clk_set_parent_before() and _after() to
> -                * to properly migrate any prepare/enable count of the orphan
> -                * clock. This is important for CLK_IS_CRITICAL clocks, which
> -                * are enabled during init but might not have a parent yet.
> -                */
> -               if (parent) {
> -                       /* update the clk tree topology */
> -                       __clk_set_parent_before(orphan, parent);
> -                       __clk_set_parent_after(orphan, parent, NULL);
> -                       __clk_recalc_accuracies(orphan);
> -                       __clk_recalc_rates(orphan, 0);
> -               }
> -       }
>  
>         kref_init(&core->ref);
>  out:
> @@ -4288,6 +4295,10 @@ int of_clk_add_provider(struct device_node *np,
>         mutex_unlock(&of_clk_mutex);
>         pr_debug("Added clock from %pOF\n", np);
>  
> +       clk_prepare_lock();
> +       __clk_core_reparent_orphan();
> +       clk_prepare_unlock();
> +

Maybe make a locked version of this function and an unlocked version?

>         ret = of_clk_set_defaults(np, true);
>         if (ret < 0)
>                 of_clk_del_provider(np);
> @@ -4323,6 +4334,10 @@ int of_clk_add_hw_provider(struct device_node *np,
>         mutex_unlock(&of_clk_mutex);
>         pr_debug("Added clk_hw provider from %pOF\n", np);
>  
> +       clk_prepare_lock();
> +       __clk_core_reparent_orphan();
> +       clk_prepare_unlock();
> +

So we don't duplicate this twice.

>         ret = of_clk_set_defaults(np, true);
>         if (ret < 0)