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, 19 insertions, 53 deletions

diff --git a/drivers/base/regmap/regcache.c b/drivers/base/regmap/regcache.c
index e2abd0548e7b..d6c2d691b6e8 100644
--- a/drivers/base/regmap/regcache.c
+++ b/drivers/base/regmap/regcache.c
@@ -121,8 +121,6 @@ int regcache_init(struct regmap *map, const struct regmap_config *config)
 	map->reg_defaults_raw = config->reg_defaults_raw;
 	map->cache_word_size = DIV_ROUND_UP(config->val_bits, 8);
 	map->cache_size_raw = map->cache_word_size * config->num_reg_defaults_raw;
-	map->cache_present = NULL;
-	map->cache_present_nbits = 0;
 
 	map->cache = NULL;
 	map->cache_ops = cache_types[i];
@@ -181,7 +179,6 @@ void regcache_exit(struct regmap *map)
 
 	BUG_ON(!map->cache_ops);
 
-	kfree(map->cache_present);
 	kfree(map->reg_defaults);
 	if (map->cache_free)
 		kfree(map->reg_defaults_raw);
@@ -407,22 +404,16 @@ EXPORT_SYMBOL_GPL(regcache_sync_region);
 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))
+	if (!map->cache_ops || !map->cache_ops->drop)
 		return -EINVAL;
 
 	map->lock(map->lock_arg);
 
 	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);
+	ret = map->cache_ops->drop(map, min, max);
 
 	map->unlock(map->lock_arg);
 
@@ -490,42 +481,6 @@ void regcache_cache_bypass(struct regmap *map, bool enable)
 }
 EXPORT_SYMBOL_GPL(regcache_cache_bypass);
 
-int regcache_set_reg_present(struct regmap *map, unsigned int reg)
-{
-	unsigned long *cache_present;
-	unsigned int cache_present_size;
-	unsigned int nregs;
-	int i;
-
-	nregs = reg + 1;
-	cache_present_size = BITS_TO_LONGS(nregs);
-	cache_present_size *= sizeof(long);
-
-	if (!map->cache_present) {
-		cache_present = kmalloc(cache_present_size, GFP_KERNEL);
-		if (!cache_present)
-			return -ENOMEM;
-		bitmap_zero(cache_present, nregs);
-		map->cache_present = cache_present;
-		map->cache_present_nbits = nregs;
-	}
-
-	if (nregs > map->cache_present_nbits) {
-		cache_present = krealloc(map->cache_present,
-					 cache_present_size, GFP_KERNEL);
-		if (!cache_present)
-			return -ENOMEM;
-		for (i = 0; i < nregs; i++)
-			if (i >= map->cache_present_nbits)
-				clear_bit(i, cache_present);
-		map->cache_present = cache_present;
-		map->cache_present_nbits = nregs;
-	}
-
-	set_bit(reg, map->cache_present);
-	return 0;
-}
-
 bool regcache_set_val(struct regmap *map, void *base, unsigned int idx,
 		      unsigned int val)
 {
@@ -617,7 +572,16 @@ int regcache_lookup_reg(struct regmap *map, unsigned int reg)
 		return -ENOENT;
 }
 
+static bool regcache_reg_present(unsigned long *cache_present, unsigned int idx)
+{
+	if (!cache_present)
+		return true;
+
+	return test_bit(idx, cache_present);
+}
+
 static int regcache_sync_block_single(struct regmap *map, void *block,
+				      unsigned long *cache_present,
 				      unsigned int block_base,
 				      unsigned int start, unsigned int end)
 {
@@ -627,7 +591,7 @@ static int regcache_sync_block_single(struct regmap *map, void *block,
 	for (i = start; i < end; i++) {
 		regtmp = block_base + (i * map->reg_stride);
 
-		if (!regcache_reg_present(map, regtmp))
+		if (!regcache_reg_present(cache_present, i))
 			continue;
 
 		val = regcache_get_val(map, block, i);
@@ -678,6 +642,7 @@ static int regcache_sync_block_raw_flush(struct regmap *map, const void **data,
 }
 
 static int regcache_sync_block_raw(struct regmap *map, void *block,
+			    unsigned long *cache_present,
 			    unsigned int block_base, unsigned int start,
 			    unsigned int end)
 {
@@ -690,7 +655,7 @@ static int regcache_sync_block_raw(struct regmap *map, void *block,
 	for (i = start; i < end; i++) {
 		regtmp = block_base + (i * map->reg_stride);
 
-		if (!regcache_reg_present(map, regtmp)) {
+		if (!regcache_reg_present(cache_present, i)) {
 			ret = regcache_sync_block_raw_flush(map, &data,
 							    base, regtmp);
 			if (ret != 0)
@@ -721,13 +686,14 @@ static int regcache_sync_block_raw(struct regmap *map, void *block,
 }
 
 int regcache_sync_block(struct regmap *map, void *block,
+			unsigned long *cache_present,
 			unsigned int block_base, unsigned int start,
 			unsigned int end)
 {
 	if (regmap_can_raw_write(map))
-		return regcache_sync_block_raw(map, block, block_base,
-					       start, end);
+		return regcache_sync_block_raw(map, block, cache_present,
+					       block_base, start, end);
 	else
-		return regcache_sync_block_single(map, block, block_base,
-						  start, end);
+		return regcache_sync_block_single(map, block, cache_present,
+						  block_base, start, end);
 }