linux-kernel - Re: [PATCH 1/3] drivers: clk: Add clk_get

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Message-ID: <152148371542.242365.18433130635050412528@swboyd.mtv.corp.google.com>
Date:   Mon, 19 Mar 2018 11:21:55 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     Jolly Shah <jolly.shah@...inx.com>, linux-clk@...r.kernel.org,
        mark.rutland@....com, michal.simek@...inx.com,
        mturquette@...libre.com, robh+dt@...nel.org, sboyd@...eaurora.org
Cc:     rajanv@...inx.com, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Jolly Shah <jolly.shah@...inx.com>,
        Jolly Shah <jollys@...inx.com>,
        Tejas Patel <tejasp@...inx.com>,
        Shubhrajyoti Datta <shubhrajyoti.datta@...inx.com>
Subject: Re: [PATCH 1/3] drivers: clk: Add clk_get_children support

Quoting Jolly Shah (2018-02-28 14:27:39)
> From: Jolly Shah <jolly.shah@...inx.com>
> 
> This API helps to determine the users for any clock.

Ok, but why do you need it?

> 
> Signed-off-by: Jolly Shah <jollys@...inx.com>
> Signed-off-by: Tejas Patel <tejasp@...inx.com>
> Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@...inx.com>
> ---
>  drivers/clk/clk.c            | 28 ++++++++++++++++++++++++++++
>  include/linux/clk-provider.h |  1 +
>  2 files changed, 29 insertions(+)
> 
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index 0f686a9..947a18b 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -274,6 +274,34 @@ struct clk_hw *clk_hw_get_parent(const struct clk_hw *hw)
>  }
>  EXPORT_SYMBOL_GPL(clk_hw_get_parent);
>  
> +static unsigned int sibling;

Looks very thread unsafe!

> +
> +static void clk_show_subtree(struct clk_core *c,
> +                            int level)
> +{
> +       struct clk_core *child;
> +
> +       if (!c)
> +               return;
> +
> +       if (level == 1)
> +               sibling++;
> +
> +       hlist_for_each_entry(child, &c->children, child_node)
> +               clk_show_subtree(child, level + 1);
> +}
> +
> +unsigned int clk_get_children(char *name)
> +{
> +       struct clk_core *core;
> +       struct clk *pclk = __clk_lookup(name);
> +
> +       sibling = 0;
> +       core = pclk->core;
> +       clk_show_subtree(core, 0);
> +       return sibling;
> +}
> +
>  static struct clk_core *__clk_lookup_subtree(const char *name,
>                                              struct clk_core *core)
>  {
> diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
> index f711be6..e94dfb2 100644
> --- a/include/linux/clk-provider.h
> +++ b/include/linux/clk-provider.h
> @@ -745,6 +745,7 @@ unsigned int __clk_get_enable_count(struct clk *clk);
>  unsigned long clk_hw_get_rate(const struct clk_hw *hw);
>  unsigned long __clk_get_flags(struct clk *clk);
>  unsigned long clk_hw_get_flags(const struct clk_hw *hw);
> +unsigned int clk_get_children(char *name);

And uses a string lookup instead of having the clk_hw pointer in hand.
No thanks.