On Fri, Jun 14, 2024 at 9:04 AM Peter Griffin <peter.griffin@xxxxxxxxxx> 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@xxxxxxxxxx>
> ---
Reviewed-by: Sam Protsenko <semen.protsenko@xxxxxxxxxx>
> 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
>
