linux-kernel - Re: [PATCH 1/2] mfd: syscon: add of_syscon_register

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Message-ID: <CAPLW+4my8dw7BmF242vbsp9iaPGjgP47Tc5Bz6U2kL5bBHRpwg@mail.gmail.com>
Date: Tue, 18 Jun 2024 12:50:59 -0500
From: Sam Protsenko <semen.protsenko@...aro.org>
To: Peter Griffin <peter.griffin@...aro.org>
Cc: lee@...nel.org, arnd@...db.de, krzk@...nel.org, alim.akhtar@...sung.com, 
	linux-arm-kernel@...ts.infradead.org, linux-samsung-soc@...r.kernel.org, 
	linux-kernel@...r.kernel.org, tudor.ambarus@...aro.org, 
	andre.draszik@...aro.org, saravanak@...gle.com, willmcvicker@...gle.com, 
	kernel-team@...roid.com
Subject: Re: [PATCH 1/2] mfd: syscon: add of_syscon_register_regmap() API

On Fri, Jun 14, 2024 at 9:04 AM Peter Griffin <peter.griffin@...aro.org> wrote:
>
> The of_syscon_register_regmap() API allows an externally created regmap
> to be registered with syscon. This regmap can then be returned to client
> drivers using the syscon_regmap_lookup_by_phandle() APIs.
>
> The API is used by platforms where mmio access to the syscon registers is
> not possible, and a underlying soc driver like exynos-pmu provides a SoC
> specific regmap that can issue a SMC or hypervisor call to write the
> register.
>
> This approach keeps the SoC complexities out of syscon, but allows common
> drivers such as  syscon-poweroff, syscon-reboot and friends that are used
> by many SoCs already to be re-used.
>
> Signed-off-by: Peter Griffin <peter.griffin@...aro.org>
> ---

Reviewed-by: Sam Protsenko <semen.protsenko@...aro.org>

>  drivers/mfd/syscon.c       | 48 ++++++++++++++++++++++++++++++++++++++
>  include/linux/mfd/syscon.h |  8 +++++++
>  2 files changed, 56 insertions(+)
>
> diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c
> index 7d0e91164cba..44991da3ea23 100644
> --- a/drivers/mfd/syscon.c
> +++ b/drivers/mfd/syscon.c
> @@ -192,6 +192,54 @@ static struct regmap *device_node_get_regmap(struct device_node *np,
>         return syscon->regmap;
>  }
>
> +/**
> + * of_syscon_register_regmap() - Register regmap for specified device node
> + * @np: Device tree node
> + * @regmap: Pointer to regmap object
> + *
> + * Register an externally created regmap object with syscon for the specified
> + * device tree node. This regmap can then be returned to client drivers using
> + * the syscon_regmap_lookup_by_phandle() API.
> + *
> + * Return: 0 on success, negative error code on failure.
> + */
> +int of_syscon_register_regmap(struct device_node *np, struct regmap *regmap)
> +{
> +       struct syscon  *entry, *syscon = NULL;
> +
> +       if (!np || !regmap)
> +               return -EINVAL;
> +
> +       /* check if syscon entry already exists */
> +       spin_lock(&syscon_list_slock);
> +
> +       list_for_each_entry(entry, &syscon_list, list)
> +               if (entry->np == np) {
> +                       syscon = entry;
> +                       break;
> +               }
> +
> +       spin_unlock(&syscon_list_slock);
> +
> +       if (syscon)
> +               return -EEXIST;
> +
> +       syscon = kzalloc(sizeof(*syscon), GFP_KERNEL);
> +       if (!syscon)
> +               return -ENOMEM;
> +
> +       syscon->regmap = regmap;
> +       syscon->np = np;
> +
> +       /* register the regmap in syscon list */
> +       spin_lock(&syscon_list_slock);
> +       list_add_tail(&syscon->list, &syscon_list);
> +       spin_unlock(&syscon_list_slock);
> +
> +       return 0;
> +}
> +EXPORT_SYMBOL_GPL(of_syscon_register_regmap);
> +
>  struct regmap *device_node_to_regmap(struct device_node *np)
>  {
>         return device_node_get_regmap(np, false);
> diff --git a/include/linux/mfd/syscon.h b/include/linux/mfd/syscon.h
> index c315903f6dab..aad9c6b50463 100644
> --- a/include/linux/mfd/syscon.h
> +++ b/include/linux/mfd/syscon.h
> @@ -28,6 +28,8 @@ struct regmap *syscon_regmap_lookup_by_phandle_args(struct device_node *np,
>                                                     unsigned int *out_args);
>  struct regmap *syscon_regmap_lookup_by_phandle_optional(struct device_node *np,
>                                                         const char *property);
> +int of_syscon_register_regmap(struct device_node *np,
> +                             struct regmap *regmap);
>  #else
>  static inline struct regmap *device_node_to_regmap(struct device_node *np)
>  {
> @@ -67,6 +69,12 @@ static inline struct regmap *syscon_regmap_lookup_by_phandle_optional(
>         return NULL;
>  }
>
> +static inline int of_syscon_register_regmap(struct device_node *np,
> +                                       struct regmap *regmap)
> +{
> +       return -EOPNOTSUPP;
> +}
> +
>  #endif
>
>  #endif /* __LINUX_MFD_SYSCON_H__ */
> --
> 2.45.2.627.g7a2c4fd464-goog
>