[PATCH] regcache: Warn if regcache_sync() is called in cache_only mode

[phucduc.bui@gmail.com]

From: bui duc phuc <phucduc.bui@gmail.com>

Calling regcache_sync() while cache_only is enabled is invalid API
usage, since writes are intentionally kept in the cache and cannot
be synchronized to hardware.
Document that callers must disable cache_only before calling
regcache_sync(), and reject incorrect usage with a WARN_ON() and
-EINVAL.

Signed-off-by: bui duc phuc <phucduc.bui@gmail.com>
---
 drivers/base/regmap/regcache.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/base/regmap/regcache.c b/drivers/base/regmap/regcache.c
index 96cdae25b9c4..d786cc8bf4d8 100644
--- a/drivers/base/regmap/regcache.c
+++ b/drivers/base/regmap/regcache.c
@@ -397,6 +397,10 @@ static int rbtree_all(const void *key, const struct rb_node *node)
  * volatile.  In general drivers can choose not to use the provided
  * syncing functionality if they so require.
  *
+ * This pushes cached changes made while cache_only (e.g. suspend) down
+ * to hardware. The caller must clear cache_only first, or writes will
+ * only update the cache.
+ *
  * Return a negative value on failure, 0 on success.
  */
 int regcache_sync(struct regmap *map)
@@ -411,6 +415,9 @@ int regcache_sync(struct regmap *map)
 	if (WARN_ON(map->cache_type == REGCACHE_NONE))
 		return -EINVAL;
 
+	if (WARN_ON(map->cache_only))
+		return -EINVAL;
+
 	BUG_ON(!map->cache_ops);
 
 	map->lock(map->lock_arg);
-- 
2.43.0