regmap: rbtree: Make cache_present bitmap per node

With devices which have a dense and small register map but placed at a large
offset the global cache_present bitmap imposes a huge memory overhead. Making
the cache_present per rbtree node avoids the issue and easily reduces the memory
footprint by a factor of ten. For devices with a more sparse map or without a
large base register offset the memory usage might increase slightly by a few
bytes, but not significantly. E.g. for a device which has ~50 registers at
offset 0x4000 the memory footprint of the register cache goes down form 2496
bytes to 175 bytes.

Moving the bitmap to a per node basis means that the handling of the bitmap is
now cache implementation specific and can no longer be managed by the core. The
regcache_sync_block() function is extended by a additional parameter so that the
cache implementation can tell the core which registers in the block are set and
which are not. The parameter is optional and if NULL the core assumes that all
registers are set. The rbtree cache also needs to implement its own drop
callback instead of relying on the core to handle this.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@linaro.org>

1 files changed, 1 insertions, 13 deletions

diff --git a/drivers/base/regmap/internal.h b/drivers/base/regmap/internal.h
index 5308e3e870ba..57f777835d97 100644
--- a/drivers/base/regmap/internal.h
+++ b/drivers/base/regmap/internal.h
@@ -128,9 +128,6 @@ struct regmap {
 	void *cache;
 	u32 cache_dirty;
 
-	unsigned long *cache_present;
-	unsigned int cache_present_nbits;
-
 	struct reg_default *patch;
 	int patch_regs;
 
@@ -203,6 +200,7 @@ int regcache_write(struct regmap *map,
 			unsigned int reg, unsigned int value);
 int regcache_sync(struct regmap *map);
 int regcache_sync_block(struct regmap *map, void *block,
+			unsigned long *cache_present,
 			unsigned int block_base, unsigned int start,
 			unsigned int end);
 
@@ -218,16 +216,6 @@ unsigned int regcache_get_val(struct regmap *map, const void *base,
 bool regcache_set_val(struct regmap *map, void *base, unsigned int idx,
 		      unsigned int val);
 int regcache_lookup_reg(struct regmap *map, unsigned int reg);
-int regcache_set_reg_present(struct regmap *map, unsigned int reg);
-
-static inline bool regcache_reg_present(struct regmap *map, unsigned int reg)
-{
-	if (!map->cache_present)
-		return false;
-	if (reg > map->cache_present_nbits)
-		return false;
-	return map->cache_present[BIT_WORD(reg)] & BIT_MASK(reg);
-}
 
 int _regmap_raw_write(struct regmap *map, unsigned int reg,
 		      const void *val, size_t val_len, bool async);