regmap: Add support for discarding parts of the register cache

Allow drivers to discard parts of the register cache, for example if part
of the hardware has been reset.

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

drivers/base/regmap/internal.h

@@ -148,6 +148,7 @@ struct regcache_ops {
 	int (*read)(struct regmap *map, unsigned int reg, unsigned int *value);
 	int (*write)(struct regmap *map, unsigned int reg, unsigned int value);
 	int (*sync)(struct regmap *map, unsigned int min, unsigned int max);
+	int (*drop)(struct regmap *map, unsigned int min, unsigned int max);
 };
 
 bool regmap_writeable(struct regmap *map, unsigned int reg);

drivers/base/regmap/regcache.c

@@ -358,6 +358,43 @@ out:
 }
 EXPORT_SYMBOL_GPL(regcache_sync_region);
 
+/**
+ * regcache_drop_region: Discard part of the register cache
+ *
+ * @map: map to operate on
+ * @min: first register to discard
+ * @max: last register to discard
+ *
+ * Discard part of the register cache.
+ *
+ * Return a negative value on failure, 0 on success.
+ */
+int regcache_drop_region(struct regmap *map, unsigned int min,
+			 unsigned int max)
+{
+	unsigned int reg;
+	int ret = 0;
+
+	if (!map->cache_present && !(map->cache_ops && map->cache_ops->drop))
+		return -EINVAL;
+
+	map->lock(map);
+
+	trace_regcache_drop_region(map->dev, min, max);
+
+	if (map->cache_present)
+		for (reg = min; reg < max + 1; reg++)
+			clear_bit(reg, map->cache_present);
+
+	if (map->cache_ops && map->cache_ops->drop)
+		ret = map->cache_ops->drop(map, min, max);
+
+	map->unlock(map);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(regcache_drop_region);
+
 /**
  * regcache_cache_only: Put a register map into cache only mode
  *

include/linux/regmap.h

@@ -394,6 +394,8 @@ bool regmap_can_raw_write(struct regmap *map);
 int regcache_sync(struct regmap *map);
 int regcache_sync_region(struct regmap *map, unsigned int min,
 			 unsigned int max);
+int regcache_drop_region(struct regmap *map, unsigned int min,
+			 unsigned int max);
 void regcache_cache_only(struct regmap *map, bool enable);
 void regcache_cache_bypass(struct regmap *map, bool enable);
 void regcache_mark_dirty(struct regmap *map);
@@ -562,6 +564,13 @@ static inline int regcache_sync_region(struct regmap *map, unsigned int min,
 	return -EINVAL;
 }
 
+static inline int regcache_drop_region(struct regmap *map, unsigned int min,
+				       unsigned int max)
+{
+	WARN_ONCE(1, "regmap API is disabled");
+	return -EINVAL;
+}
+
 static inline void regcache_cache_only(struct regmap *map, bool enable)
 {
 	WARN_ONCE(1, "regmap API is disabled");

include/trace/events/regmap.h

@@ -223,6 +223,29 @@ DEFINE_EVENT(regmap_async, regmap_async_complete_done,
 
 );
 
+TRACE_EVENT(regcache_drop_region,
+
+	TP_PROTO(struct device *dev, unsigned int from,
+		 unsigned int to),
+
+	TP_ARGS(dev, from, to),
+
+	TP_STRUCT__entry(
+		__string(       name,           dev_name(dev)   )
+		__field(	unsigned int,	from		)
+		__field(	unsigned int,	to		)
+	),
+
+	TP_fast_assign(
+		__assign_str(name, dev_name(dev));
+		__entry->from = from;
+		__entry->to = to;
+	),
+
+	TP_printk("%s %u-%u", __get_str(name), (unsigned int)__entry->from,
+		  (unsigned int)__entry->to)
+);
+
 #endif /* _TRACE_REGMAP_H */
 
 /* This part must be outside protection */