mfd: syscon: Add of_syscon_register_regmap() API

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@linaro.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Sam Protsenko <semen.protsenko@linaro.org>
Tested-by: Will McVicker <willmcvicker@google.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20240621115544.1655458-2-peter.griffin@linaro.org
Signed-off-by: Lee Jones <lee@kernel.org>

diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c
index 7d0e91164cbaa3dde29f7d517b28bef2f8861179..33f1e07ab24dc27a36a607aa11e1df4e70643685 100644 (file)
--- 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 c315903f6dab3dc7a4eb95b0757d9939b0e817b6..aad9c6b5046368992277e21a6770a0934b686240 100644 (file)
--- 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__ */