drivers: regulator: add regulator_dt_get_supply()

Implements regulator_dt_get_supply() API function for consumer
drivers to get a regulator supply using the driver device DT node
data. The function returns TEE_ERROR_DEFER_DRIVER_INIT when the
target supply exists but is yet not initialized.

Acked-by: Gatien Chevallier <gatien.chevallier@foss.st.com>
Co-developed-by: Pascal Paillet <p.paillet@foss.st.com>
Signed-off-by: Pascal Paillet <p.paillet@foss.st.com>
Signed-off-by: Etienne Carriere <etienne.carriere@foss.st.com>

core/drivers/regulator/regulator_dt.c

@@ -107,6 +107,29 @@ static TEE_Result get_supply_phandle(const void *fdt, int node,
 	return TEE_SUCCESS;
 }
 
+TEE_Result regulator_dt_get_supply(const void *fdt, int node,
+				   const char *supply_name,
+				   struct regulator **regulator)
+{
+	struct dt_driver_provider *provider = NULL;
+	TEE_Result res = TEE_ERROR_GENERIC;
+	uint32_t supply_phandle = 0;
+
+	res = get_supply_phandle(fdt, node, supply_name, &supply_phandle);
+	if (res)
+		return res;
+
+	provider = dt_driver_get_provider_by_phandle(supply_phandle,
+						     DT_DRIVER_REGULATOR);
+	if (!provider)
+		return TEE_ERROR_DEFER_DRIVER_INIT;
+
+	*regulator = dt_driver_provider_priv_data(provider);
+	assert(*regulator);
+
+	return TEE_SUCCESS;
+}
+
 /* Helper function to register a regulator provider instance */
 static TEE_Result regulator_register_provider(const void *fdt, int node,
 					      struct regulator *regulator)

core/include/drivers/regulator.h

@@ -197,6 +197,23 @@ static inline void regulator_print_state(const char *message __unused)
 #endif /*CFG_DRIVERS_REGULATOR*/
 
 #if defined(CFG_DRIVERS_REGULATOR) && defined(CFG_DT)
+/*
+ * regulator_dt_get_supply() - Get a regulator supply from name and DT node
+ * @fdt: FDT to work on
+ * @node: DT node of the regulator consumer
+ * @supply_name: Name of the supply in DT property xxx-supply
+ * @regulator: Output regulator upon success
+ *
+ * Upon success, this function provides the pointer to regulator
+ * defined by DT binding property @name-supply phandle reference.
+ *
+ * This function returns TEE_ERROR_DEFER_DRIVER_INIT if supply exists but is
+ * not yet initialized.
+ */
+TEE_Result regulator_dt_get_supply(const void *fdt, int node,
+				   const char *supply_name,
+				   struct regulator **regulator);
+
 /*
  * regulator_dt_register() - Register a regulator to related to a DT node
  * @fdt: FDT to work on