[PATCH v5 2/2] regcache: Move HW readback after cache initialisation

[Andy Shevchenko]

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@xxxxxxxxxxxxxxx>
---
 drivers/base/regmap/regcache.c | 33 +++++++++++++++++++++------------
 1 file changed, 21 insertions(+), 12 deletions(-)

diff --git a/drivers/base/regmap/regcache.c b/drivers/base/regmap/regcache.c
index 329cdee1ae1c..5beada4ca64c 100644
--- a/drivers/base/regmap/regcache.c
+++ b/drivers/base/regmap/regcache.c
@@ -66,6 +66,14 @@ static int regcache_hw_init(struct regmap *map, int count)
 	unsigned int reg, val;
 	void *tmp_buf;
 
+	/*
+	 * When count is zero, it means there is nothing to cache and hence
+	 * nothing to read back from HW to set up defaults, so skip this phase
+	 * without an error code returned.
+	 */
+	if (!count)
+		return 0;
+
 	map->num_reg_defaults = count;
 	map->reg_defaults = kmalloc_objs(struct reg_default, count);
 	if (!map->reg_defaults)
@@ -208,14 +216,6 @@ int regcache_init(struct regmap *map, const struct regmap_config *config)
 		count = regcache_count_cacheable_registers(map);
 		if (map->cache_bypass)
 			return 0;
-
-		/* 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, count);
-		if (ret < 0)
-			return ret;
 	}
 
 	if (!map->max_register_is_set && map->num_reg_defaults_raw) {
@@ -230,9 +230,18 @@ 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;
+			return ret;
 	}
 
+	/*
+	 * 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, count);
+	if (ret)
+		goto err_exit;
+
 	if (map->cache_ops->populate &&
 	    (map->num_reg_defaults || map->reg_default_cb)) {
 		dev_dbg(map->dev, "Populating %s cache\n", map->cache_ops->name);
@@ -240,10 +249,12 @@ 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);
@@ -251,8 +262,6 @@ int regcache_init(struct regmap *map, const struct regmap_config *config)
 		ret = map->cache_ops->exit(map);
 		map->unlock(map->lock_arg);
 	}
-err_free:
-	regcache_hw_exit(map);
 
 	return ret;
 }
-- 
2.50.1