Merge tag 'regmap-fix-v6.4-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/regmap

Pull regmap fix from Mark Brown:
 "Another fix for the maple tree cache, Takashi noticed that unlike
  other caches the maple tree cache didn't check for read only registers
  before trying to sync which would result in spurious syncs for read
  only registers where we don't have a default.

  This was due to the check being open coded in the caches, we now check
  in the shared 'does this register need sync' function so that is fixed
  for this and future caches"

* tag 'regmap-fix-v6.4-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/regmap:
  regmap: regcache: Don't sync read-only registers

Author: torvalds

drivers/base/regmap/regcache.c

@@ -284,6 +284,9 @@ static bool regcache_reg_needs_sync(struct regmap *map, unsigned int reg,
 {
 	int ret;
 
+	if (!regmap_writeable(map, reg))
+		return false;
+
 	/* If we don't know the chip just got reset, then sync everything. */
 	if (!map->no_sync_defaults)
 		return true;