regmap: Track if the register cache is dirty and suppress unneeded syncs

Allow drivers to optimise out the register cache sync if they didn't need
to do one. If the hardware is desynced from the register cache (by power
loss for example) then the driver should call regcache_mark_dirty() to
let the core know about this.

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

4 files changed, 24 insertions, 1 deletions

diff --git a/drivers/base/regmap/internal.h b/drivers/base/regmap/internal.h
index 348ff02eb93e..6483e0bda0cf 100644
--- a/drivers/base/regmap/internal.h
+++ b/drivers/base/regmap/internal.h
@@ -74,6 +74,7 @@ struct regmap {
         struct reg_default *reg_defaults;
         const void *reg_defaults_raw;
         void *cache;
+        bool cache_dirty;
 };
 
 struct regcache_ops {
diff --git a/drivers/base/regmap/regcache.c b/drivers/base/regmap/regcache.c
index 666f6f5011dc..6ab9f0384d82 100644
--- a/drivers/base/regmap/regcache.c
+++ b/drivers/base/regmap/regcache.c
@@ -241,6 +241,8 @@ int regcache_sync(struct regmap *map)
                 map->cache_ops->name);
         name = map->cache_ops->name;
         trace_regcache_sync(map->dev, name, "start");
+        if (!map->cache_dirty)
+                goto out;
         if (map->cache_ops->sync) {
                 ret = map->cache_ops->sync(map);
         } else {
@@ -291,6 +293,23 @@ void regcache_cache_only(struct regmap *map, bool enable)
 EXPORT_SYMBOL_GPL(regcache_cache_only);
 
 /**
+ * regcache_mark_dirty: Mark the register cache as dirty
+ *
+ * @map: map to mark
+ *
+ * Mark the register cache as dirty, for example due to the device
+ * having been powered down for suspend.  If the cache is not marked
+ * as dirty then the cache sync will be suppressed.
+ */
+void regcache_mark_dirty(struct regmap *map)
+{
+        mutex_lock(&map->lock);
+        map->cache_dirty = true;
+        mutex_unlock(&map->lock);
+}
+EXPORT_SYMBOL_GPL(regcache_mark_dirty);
+
+/**
  * regcache_cache_bypass: Put a register map into cache bypass mode
  *
  * @map: map to configure
diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index bf441db1ee90..3aca18dbf367 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -306,8 +306,10 @@ int _regmap_write(struct regmap *map, unsigned int reg,
                 ret = regcache_write(map, reg, val);
                 if (ret != 0)
                         return ret;
-                if (map->cache_only)
+                if (map->cache_only) {
+                        map->cache_dirty = true;
                         return 0;
+                }
         }
 
         trace_regmap_reg_write(map->dev, reg, val);
diff --git a/include/linux/regmap.h b/include/linux/regmap.h
index 690276a642cf..32043a9749e6 100644
--- a/include/linux/regmap.h
+++ b/include/linux/regmap.h
@@ -143,5 +143,6 @@ int regmap_update_bits(struct regmap *map, unsigned int reg,
 int regcache_sync(struct regmap *map);
 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);
 
 #endif