regcache: Move HW readback after cache initialisation

Make sure that cache is initialised before calling any IO
using regmap, this makes sure that we won't access NULL or
invalid pointers in the cache which hasn't been initialised.

As a side effect it also makes the ordering of cleaning up
the resources in regcache_exit() to be the same (and correct)
as in the error path of regcache_init(). This is not a problem
right now as they do not have dependencies, but it makes code
robust against potential changes in the future.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://patch.msgid.link/20260305085449.3184020-4-andriy.shevchenko@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: andy-shev

drivers/base/regmap/regcache.c

@@ -200,14 +200,6 @@ int regcache_init(struct regmap *map, const struct regmap_config *config)
 		map->reg_defaults = kmalloc_objs(struct reg_default, count);
 		if (!map->reg_defaults)
 			return -ENOMEM;
-
-		/* Some devices such as PMICs don't have cache defaults,
-		 * we cope with this by reading back the HW registers and
-		 * crafting the cache defaults by hand.
-		 */
-		ret = regcache_hw_init(map);
-		if (ret < 0)
-			goto err_free_reg_defaults;
 	}
 
 	if (!map->max_register_is_set && map->num_reg_defaults_raw) {
@@ -222,7 +214,18 @@ int regcache_init(struct regmap *map, const struct regmap_config *config)
 		ret = map->cache_ops->init(map);
 		map->unlock(map->lock_arg);
 		if (ret)
-			goto err_free;
+			goto err_free_reg_defaults;
+	}
+
+	/*
+	 * Some devices such as PMICs don't have cache defaults,
+	 * we cope with this by reading back the HW registers and
+	 * crafting the cache defaults by hand.
+	 */
+	if (count) {
+		ret = regcache_hw_init(map);
+		if (ret)
+			goto err_exit;
 	}
 
 	if (map->cache_ops->populate &&
@@ -232,19 +235,19 @@ int regcache_init(struct regmap *map, const struct regmap_config *config)
 		ret = map->cache_ops->populate(map);
 		map->unlock(map->lock_arg);
 		if (ret)
-			goto err_exit;
+			goto err_free;
 	}
 	return 0;
 
+err_free:
+	regcache_hw_exit(map);
 err_exit:
 	if (map->cache_ops->exit) {
 		dev_dbg(map->dev, "Destroying %s cache\n", map->cache_ops->name);
 		map->lock(map->lock_arg);
 		ret = map->cache_ops->exit(map);
 		map->unlock(map->lock_arg);
 	}
-err_free:
-	regcache_hw_exit(map);
 err_free_reg_defaults:
 	kfree(map->reg_defaults);