regmap: Add trace event for successful cache reads

Currently we only trace physical reads, there's no instrumentation if
the read is satisfied from cache.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

drivers/base/regmap/regcache.c

@@ -193,13 +193,21 @@ void regcache_exit(struct regmap *map)
 int regcache_read(struct regmap *map,
 		  unsigned int reg, unsigned int *value)
 {
+	int ret;
+
 	if (map->cache_type == REGCACHE_NONE)
 		return -ENOSYS;
 
 	BUG_ON(!map->cache_ops);
 
-	if (!regmap_volatile(map, reg))
-		return map->cache_ops->read(map, reg, value);
+	if (!regmap_volatile(map, reg)) {
+		ret = map->cache_ops->read(map, reg, value);
+
+		if (ret == 0)
+			trace_regmap_reg_read_cache(map->dev, reg, *value);
+
+		return ret;
+	}
 
 	return -EINVAL;
 }

include/trace/events/regmap.h

@@ -55,6 +55,15 @@ DEFINE_EVENT(regmap_reg, regmap_reg_read,
 
 );
 
+DEFINE_EVENT(regmap_reg, regmap_reg_read_cache,
+
+	TP_PROTO(struct device *dev, unsigned int reg,
+		 unsigned int val),
+
+	TP_ARGS(dev, reg, val)
+
+);
+
 DECLARE_EVENT_CLASS(regmap_block,
 
 	TP_PROTO(struct device *dev, unsigned int reg, int count),