[PATCH v3 07/12] reset: Add reset_control_get_from_provider_exclusive()

[Geert Uytterhoeven]

On Wed, 2 Sept 2026 at 13:30, Geert Uytterhoeven
<geert+renesas at glider.be> wrote:
> When stacking two reset controllers, the upper one should go through the
> proper channels: request exclusive reset controls and use them via the
> reset_control_*() APIs.  However, unlike the clock subsystem, which has
> of_clk_get_from_provider(), the reset subsystem does not offer a way to
> lookup and obtain a reset from a reset provider.
>
> Hence add a public helper reset_control_get_from_provider_exclusive()
> to lookup and obtain an exclusive reference to a reset controller, based
> on the recently introduced __reset_control_get_from_provider() helper.
> This will be used by the R-Car X5H Module Controller driver.
>
> Signed-off-by: Geert Uytterhoeven <geert+renesas at glider.be>
> ---
> v3:
>   - Replace reset_controller_get_provider() by
>     reset_control_get_from_provider_exclusive(),
>   - Add kerneldoc,
>
> v2:
>   - No changes.
> ---
>  drivers/reset/core.c  | 37 ++++++++++++++++++++++++++++++++-----
>  include/linux/reset.h |  8 ++++++++
>  2 files changed, 40 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/reset/core.c b/drivers/reset/core.c
> index 8af7cd2e8a5029df..6d4c95b3edb18248 100644
> --- a/drivers/reset/core.c
> +++ b/drivers/reset/core.c
> @@ -1141,6 +1141,7 @@ __reset_control_get_from_provider(const struct fwnode_reference_args *args,
>                                   bool gpio_fallback,
>                                   enum reset_control_flags flags)
>  {
> +       struct fwnode_handle *fwnode = consumer ?: args->fwnode;
>         struct reset_control *rstc = ERR_PTR(-EINVAL);
>         struct reset_controller_dev *rcdev;
>         int rstc_id = -EINVAL;
> @@ -1154,18 +1155,26 @@ __reset_control_get_from_provider(const struct fwnode_reference_args *args,
>         if (WARN_ON(args->nargs != rcdev->fwnode_reset_n_cells))
>                 return ERR_PTR(-EINVAL);
>
> -       if (rcdev->of_xlate && is_of_node(consumer)) {
> -               struct device_node *np = to_of_node(consumer);
> +       if (rcdev->of_xlate && is_of_node(fwnode)) {
> +               struct device_node *np = to_of_node(fwnode);
>                 struct of_phandle_args of_args;
>                 int ret;
>
> -               ret = of_parse_phandle_with_args(np,
> +               if (consumer) {
> +                       ret = of_parse_phandle_with_args(np,
>                                          gpio_fallback ? "reset-gpios" : "resets",
>                                          gpio_fallback ? "#gpio-cells" : "#reset-cells",
>                                          gpio_fallback ? 0 : index,
>                                          &of_args);
> -               if (ret)
> -                       return ERR_PTR(ret);
> +                       if (ret)
> +                               return ERR_PTR(ret);
> +               } else {
> +                       of_args.np = of_node_get(np);
> +                       of_args.args_count = args->nargs;
> +
> +                       for (unsigned int i = 0; i < args->nargs; i++)
> +                               of_args.args[i] = args->args[i];
> +               }
>
>                 rstc_id = rcdev->of_xlate(rcdev, &of_args);
>                 of_node_put(of_args.np);
> @@ -1257,6 +1266,24 @@ struct reset_control *__reset_control_get(struct device *dev, const char *id,
>  }
>  EXPORT_SYMBOL_GPL(__reset_control_get);
>
> +/**
> + * reset_control_get_from_provider_exclusive - Lookup and obtain an exclusive
> + *                                            reference to a reset controller.
> + * @args: Reference to the reset controller provider with all the args like
> + *       reset number
> + *
> + * Returns a struct reset_control or IS_ERR() condition containing errno.
> + * If this function is called more than once for the same reset control it will
> + * return -EBUSY.
> + */
> +struct reset_control *
> +reset_control_get_from_provider_exclusive(const struct fwnode_reference_args *args)
> +{
> +       return __reset_control_get_from_provider(args, NULL, 0, false,
> +                                                RESET_CONTROL_EXCLUSIVE);
> +}
> +EXPORT_SYMBOL_GPL(reset_control_get_from_provider_exclusive);
> +
>  int __reset_control_bulk_get(struct device *dev, int num_rstcs,
>                              struct reset_control_bulk_data *rstcs,
>                              enum reset_control_flags flags)
> diff --git a/include/linux/reset.h b/include/linux/reset.h
> index 9c391cf0c82298a0..09ee47b27f88d3b1 100644
> --- a/include/linux/reset.h
> +++ b/include/linux/reset.h
> @@ -90,6 +90,8 @@ struct reset_control *__fwnode_reset_control_get(struct fwnode_handle *fwnode,
>                                      const char *id, int index, enum reset_control_flags flags);
>  struct reset_control *__reset_control_get(struct device *dev, const char *id,
>                                           int index, enum reset_control_flags flags);
> +struct reset_control *reset_control_get_from_provider_exclusive(
> +                               const struct fwnode_reference_args *args);
>  void reset_control_put(struct reset_control *rstc);
>  int __reset_control_bulk_get(struct device *dev, int num_rstcs,
>                              struct reset_control_bulk_data *rstcs,
> @@ -173,6 +175,12 @@ static inline struct reset_control *__reset_control_get(
>         return optional ? NULL : ERR_PTR(-ENOTSUPP);
>  }
>
> +static inline struct reset_control *reset_control_get_from_provider_exclusive(
> +                               const struct fwnode_reference_args *args)
> +{
> +       return NULL;

As reported by Sashiko, this dummy should return ERR_PTR(-ENOTSUPP)
instead.

> +}
> +
>  static inline int
>  reset_control_bulk_reset(int num_rstcs, struct reset_control_bulk_data *rstcs)
>  {

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds