regcache: Validate cache_only state in regcache_sync_region()

Add a WARN_ON() check to ensure regcache_sync_region() is not called
while cache_only is enabled.

Signed-off-by: bui duc phuc <phucduc.bui@gmail.com>
Link: https://patch.msgid.link/20260720033238.52479-2-phucduc.bui@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: BuiDucPhuc

drivers/base/regmap/regcache.c

@@ -516,6 +516,10 @@ int regcache_sync_region(struct regmap *map, unsigned int min,
 
 	map->lock(map->lock_arg);
 
+	if (WARN_ON(map->cache_only)) {
+		map->unlock(map->lock_arg);
+		return -EINVAL;
+	}
 	/* Remember the initial bypass state */
 	bypass = map->cache_bypass;