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: Arnd Bergmann <arnd@xxxxxxxx> Reviewed-by: Sam Protsenko <semen.protsenko@xxxxxxxxxx> --- Changes in v3: - Move kzalloc allocation outside of spin lock (Arnd) - Link to v2 https://lore.kernel.org/linux-arm-kernel/20240620112446.1286223-2-peter.griffin@xxxxxxxxxx/ Changes in v2: - Keep syscon lock held between checking and adding entry (Krzysztof) - Link to v1 https://lore.kernel.org/linux-arm-kernel/20240614140421.3172674-2-peter.griffin@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..33f1e07ab24d 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 will 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; + int ret; + + if (!np || !regmap) + return -EINVAL; + + syscon = kzalloc(sizeof(*syscon), GFP_KERNEL); + if (!syscon) + return -ENOMEM; + + /* check if syscon entry already exists */ + spin_lock(&syscon_list_slock); + + list_for_each_entry(entry, &syscon_list, list) + if (entry->np == np) { + ret = -EEXIST; + goto err_unlock; + } + + syscon->regmap = regmap; + syscon->np = np; + + /* register the regmap in syscon list */ + list_add_tail(&syscon->list, &syscon_list); + spin_unlock(&syscon_list_slock); + + return 0; + +err_unlock: + spin_unlock(&syscon_list_slock); + kfree(syscon); + return ret; +} +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__ */ -- 2.45.2.741.gdbec12cfda-goog
