ASoC: SDCA: Add helper to write out defaults and fixed values

The concept of an SDCA default value differs slightly from the regmap
usage of the term. An SDCA default is a value that is parsed from DisCo
and then written out to the hardware if no user value has superceded
it. Add a helper function that will iterate through all the SDCA
Controls and write out any default values. After these have been written
out once they will exist in the cache and that will take care of any
user values superceeding them. The code here also writes out any
Controls with a fixed value as there is only one available value for
these Controls there is no point in allowing the user to select them,
simply treat them similarly to a default.

Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.dev>
Link: https://patch.msgid.link/20250217140159.2288784-5-ckeepax@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>

include/sound/sdca_regmap.h

@@ -12,6 +12,7 @@
 
 struct device;
 struct sdca_function_data;
+struct regmap;
 struct reg_default;
 
 bool sdca_regmap_readable(struct sdca_function_data *function, unsigned int reg);
@@ -24,4 +25,7 @@ int sdca_regmap_count_constants(struct device *dev, struct sdca_function_data *f
 int sdca_regmap_populate_constants(struct device *dev, struct sdca_function_data *function,
 				   struct reg_default *consts);
 
+int sdca_regmap_write_defaults(struct device *dev, struct regmap *regmap,
+			       struct sdca_function_data *function);
+
 #endif // __SDCA_REGMAP_H__

sound/soc/sdca/sdca_regmap.c

@@ -268,5 +268,54 @@ int sdca_regmap_populate_constants(struct device *dev,
 }
 EXPORT_SYMBOL_NS(sdca_regmap_populate_constants, "SND_SOC_SDCA");
 
+/**
+ * sdca_regmap_write_defaults - write out DisCo defaults to device
+ * @dev: Pointer to the device.
+ * @regmap: Pointer to the Function register map.
+ * @function: Pointer to the Function information, to be parsed.
+ *
+ * This function will write out to the hardware all the DisCo default and
+ * fixed value controls. This will cause them to be populated into the cache,
+ * and subsequent handling can be done through a cache sync.
+ *
+ * Return: Returns zero on success, and a negative error code on failure.
+ */
+int sdca_regmap_write_defaults(struct device *dev, struct regmap *regmap,
+			       struct sdca_function_data *function)
+{
+	int i, j;
+	int ret;
+
+	for (i = 0; i < function->num_entities; i++) {
+		struct sdca_entity *entity = &function->entities[i];
+
+		for (j = 0; j < entity->num_controls; j++) {
+			struct sdca_control *control = &entity->controls[j];
+			int cn;
+
+			if (control->mode == SDCA_ACCESS_MODE_DC)
+				continue;
+
+			if (!control->has_default && !control->has_fixed)
+				continue;
+
+			for_each_set_bit(cn, (unsigned long *)&control->cn_list,
+					 BITS_PER_TYPE(control->cn_list)) {
+				unsigned int reg;
+
+				reg = SDW_SDCA_CTL(function->desc->adr, entity->id,
+						   control->sel, cn);
+
+				ret = regmap_write(regmap, reg, control->value);
+				if (ret)
+					return ret;
+			}
+		}
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_NS(sdca_regmap_write_defaults, "SND_SOC_SDCA");
+
 MODULE_LICENSE("GPL");
 MODULE_DESCRIPTION("SDCA library");