Subject: [PATCH RFC 1/2] clk: Provide not locked variant of of_clk_get_from_provider()

From: [email-masked] (Mike Turquette)
Date: Mon, 19 Aug 2013 12:41:32 -0700

Quoting Sylwester Nawrocki (2013-08-09 09:34:05)
> Add helper functions for the of_clk_providers list locking and
> an unlocked variant of of_clk_get_from_provider().
> These functions are intended to be used in the clkdev to avoid
> race condition in the device tree based clock look up in clk_get().
> 
> Signed-off-by: Sylwester Nawrocki <[email-masked]>
> Signed-off-by: Kyungmin Park <[email-masked]>

Looks good to me.

Russell,

Any objections?

Regards,
Mike

> ---
>  drivers/clk/clk.c   |   36 ++++++++++++++++++++++++++++--------
>  include/linux/clk.h |    3 +++
>  2 files changed, 31 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index 0d4c982..8b8c152 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -2143,7 +2143,18 @@ static const struct of_device_id __clk_of_table_sentinel
>         __used __section(__clk_of_table_end);
>  
>  static LIST_HEAD(of_clk_providers);
> -static DEFINE_MUTEX(of_clk_lock);
> +static DEFINE_MUTEX(of_clk_mutex);
> +
> +/* of_clk_provider list locking helpers */
> +void of_clk_lock(void)
> +{
> +       mutex_lock(&of_clk_mutex);
> +}
> +
> +void of_clk_unlock(void)
> +{
> +       mutex_unlock(&of_clk_mutex);
> +}
>  
>  struct clk *of_clk_src_simple_get(struct of_phandle_args *clkspec,
>                                      void *data)
> @@ -2187,9 +2198,9 @@ int of_clk_add_provider(struct device_node *np,
>         cp->data = data;
>         cp->get = clk_src_get;
>  
> -       mutex_lock(&of_clk_lock);
> +       mutex_lock(&of_clk_mutex);
>         list_add(&cp->link, &of_clk_providers);
> -       mutex_unlock(&of_clk_lock);
> +       mutex_unlock(&of_clk_mutex);
>         pr_info("Added clock from %s\n", np->full_name);
>  
>         return 0;
> @@ -2204,7 +2215,7 @@ void of_clk_del_provider(struct device_node *np)
>  {
>         struct of_clk_provider *cp;
>  
> -       mutex_lock(&of_clk_lock);
> +       mutex_lock(&of_clk_mutex);
>         list_for_each_entry(cp, &of_clk_providers, link) {
>                 if (cp->node == np) {
>                         list_del(&cp->link);
> @@ -2213,24 +2224,33 @@ void of_clk_del_provider(struct device_node *np)
>                         break;
>                 }
>         }
> -       mutex_unlock(&of_clk_lock);
> +       mutex_unlock(&of_clk_mutex);
>  }
>  EXPORT_SYMBOL_GPL(of_clk_del_provider);
>  
> -struct clk *of_clk_get_from_provider(struct of_phandle_args *clkspec)
> +struct clk *__of_clk_get_from_provider(struct of_phandle_args *clkspec)
>  {
>         struct of_clk_provider *provider;
>         struct clk *clk = ERR_PTR(-ENOENT);
>  
>         /* Check if we have such a provider in our array */
> -       mutex_lock(&of_clk_lock);
>         list_for_each_entry(provider, &of_clk_providers, link) {
>                 if (provider->node == clkspec->np)
>                         clk = provider->get(clkspec, provider->data);
>                 if (!IS_ERR(clk))
>                         break;
>         }
> -       mutex_unlock(&of_clk_lock);
> +
> +       return clk;
> +}
> +
> +struct clk *of_clk_get_from_provider(struct of_phandle_args *clkspec)
> +{
> +       struct clk *clk;
> +
> +       mutex_lock(&of_clk_mutex);
> +       clk = __of_clk_get_from_provider(clkspec);
> +       mutex_unlock(&of_clk_mutex);
>  
>         return clk;
>  }
> diff --git a/include/linux/clk.h b/include/linux/clk.h
> index 9a6d045..ea6822e 100644
> --- a/include/linux/clk.h
> +++ b/include/linux/clk.h
> @@ -368,6 +368,9 @@ struct of_phandle_args;
>  struct clk *of_clk_get(struct device_node *np, int index);
>  struct clk *of_clk_get_by_name(struct device_node *np, const char *name);
>  struct clk *of_clk_get_from_provider(struct of_phandle_args *clkspec);
> +struct clk *__of_clk_get_from_provider(struct of_phandle_args *clkspec);
> +void of_clk_lock(void);
> +void of_clk_unlock(void);
>  #else
>  static inline struct clk *of_clk_get(struct device_node *np, int index)
>  {
> -- 
> 1.7.9.5