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

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

[phucduc.bui]

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

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

[Mark Brown]

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On Wed, Jul 15, 2026 at 12:21:00PM +0700, phucduc.bui@gmail.com wrote:

> @@ -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);

The check needs to be done under lock otherwise some other thread could
come in and put the regmap into cache only mode between the check and
when we take the lock.

We also need a similar check in regcache_sync_region().

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