regmap: cache: Don't attempt to sync non-writeable registers

In the regcache_default_sync, if a register isn't writeable, then
_regmap_write will return an error and the rest of the sync will be
aborted.  Avoid this by checking if a register is writeable before
trying to sync it.

Signed-off-by: Dylan Reid <dgreid@chromium.org>
Signed-off-by: Mark Brown <broonie@linaro.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/drivers/base/regmap/regcache.c b/drivers/base/regmap/regcache.c
index bb3ba42e0329..a9d8d7be6aa3 100644
--- a/drivers/base/regmap/regcache.c
+++ b/drivers/base/regmap/regcache.c
@@ -253,7 +253,8 @@ static int regcache_default_sync(struct regmap *map, unsigned int min,
                 unsigned int val;
                 int ret;
 
-                if (regmap_volatile(map, reg))
+                if (regmap_volatile(map, reg) ||
+                    !regmap_writeable(map, reg))
                         continue;
 
                 ret = regcache_read(map, reg, &val);