regmap: introduce fast_io busses, and use a spinlock for them

Some bus types have very fast IO. For these, acquiring a mutex for every
IO operation is a significant overhead. Allow busses to indicate their IO
is fast, and enhance regmap to use a spinlock for those busses.

[Currently limited to native endian registers -- broonie]

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
diff --git a/drivers/base/regmap/regcache.c b/drivers/base/regmap/regcache.c
index 87f54db..4ad1850 100644
--- a/drivers/base/regmap/regcache.c
+++ b/drivers/base/regmap/regcache.c
@@ -264,7 +264,7 @@
 
 	BUG_ON(!map->cache_ops || !map->cache_ops->sync);
 
-	mutex_lock(&map->lock);
+	map->lock(map);
 	/* Remember the initial bypass state */
 	bypass = map->cache_bypass;
 	dev_dbg(map->dev, "Syncing %s cache\n",
@@ -296,7 +296,7 @@
 	trace_regcache_sync(map->dev, name, "stop");
 	/* Restore the bypass state */
 	map->cache_bypass = bypass;
-	mutex_unlock(&map->lock);
+	map->unlock(map);
 
 	return ret;
 }
@@ -323,7 +323,7 @@
 
 	BUG_ON(!map->cache_ops || !map->cache_ops->sync);
 
-	mutex_lock(&map->lock);
+	map->lock(map);
 
 	/* Remember the initial bypass state */
 	bypass = map->cache_bypass;
@@ -342,7 +342,7 @@
 	trace_regcache_sync(map->dev, name, "stop region");
 	/* Restore the bypass state */
 	map->cache_bypass = bypass;
-	mutex_unlock(&map->lock);
+	map->unlock(map);
 
 	return ret;
 }
@@ -361,11 +361,11 @@
  */
 void regcache_cache_only(struct regmap *map, bool enable)
 {
-	mutex_lock(&map->lock);
+	map->lock(map);
 	WARN_ON(map->cache_bypass && enable);
 	map->cache_only = enable;
 	trace_regmap_cache_only(map->dev, enable);
-	mutex_unlock(&map->lock);
+	map->unlock(map);
 }
 EXPORT_SYMBOL_GPL(regcache_cache_only);
 
@@ -380,9 +380,9 @@
  */
 void regcache_mark_dirty(struct regmap *map)
 {
-	mutex_lock(&map->lock);
+	map->lock(map);
 	map->cache_dirty = true;
-	mutex_unlock(&map->lock);
+	map->unlock(map);
 }
 EXPORT_SYMBOL_GPL(regcache_mark_dirty);
 
@@ -399,11 +399,11 @@
  */
 void regcache_cache_bypass(struct regmap *map, bool enable)
 {
-	mutex_lock(&map->lock);
+	map->lock(map);
 	WARN_ON(map->cache_only && enable);
 	map->cache_bypass = enable;
 	trace_regmap_cache_bypass(map->dev, enable);
-	mutex_unlock(&map->lock);
+	map->unlock(map);
 }
 EXPORT_SYMBOL_GPL(regcache_cache_bypass);