Throughout the regcache-flat code, for the flat cache array, the
actual register address offsets are used to index the values, and
this will waste some memory spaces.
For example, on 64-BIT platform, device A has three registers:
register offsets: {0x00, 0x08, 0x10}
max_register: 0x10
regsiter striding: 8
And the size of flat cache memory space will be:
(max_register + 1 ) * sizeof(unsigned int) =
(0x10 + 1) * sizeof(unsigned int) = 17 * 8 = 136 Bytes
Since map->reg_stride has been introduced and all extant register
addresses are a multiple of this value, it could use the address
offsets divide by the stride to determine the index.
Then the size of flat cache memory space will be:
(max_register / reg_stride + 1 ) * sizeof(unsigned int) =
(0x10 / 8 + 1) * sizeof(unsigned int) = 3 * 8 = 24 Bytes
And the bigger of the striding value, there will be more memory
space wasted. After introducing the register striding here can
save some memeories for the system.
Signed-off-by: Xiubo Li <lixi...@cmss.chinamobile.com>
---
drivers/base/regmap/regcache-flat.c | 18 +++++++++++-------
1 file changed, 11 insertions(+), 7 deletions(-)
diff --git a/drivers/base/regmap/regcache-flat.c
b/drivers/base/regmap/regcache-flat.c
index 686c9e0..160d636 100644
--- a/drivers/base/regmap/regcache-flat.c
+++ b/drivers/base/regmap/regcache-flat.c
@@ -19,17 +19,19 @@
static int regcache_flat_init(struct regmap *map)
{
int i;
- unsigned int *cache;
+ unsigned int index, *cache;
- map->cache = kcalloc(map->max_register + 1, sizeof(unsigned int),
- GFP_KERNEL);
+ map->cache = kcalloc(map->max_register / map->reg_stride + 1,
+ sizeof(unsigned int), GFP_KERNEL);
if (!map->cache)
return -ENOMEM;
cache = map->cache;
- for (i = 0; i < map->num_reg_defaults; i++)
- cache[map->reg_defaults[i].reg] = map->reg_defaults[i].def;
+ for (i = 0; i < map->num_reg_defaults; i++) {
+ index = map->reg_defaults[i].reg / map->reg_stride;
+ cache[index] = map->reg_defaults[i].def;
+ }
return 0;
}
@@ -45,9 +47,10 @@ static int regcache_flat_exit(struct regmap *map)
static int regcache_flat_read(struct regmap *map,
unsigned int reg, unsigned int *value)
{
+ unsigned int index = reg / map->reg_stride;
unsigned int *cache = map->cache;
- *value = cache[reg];
+ *value = cache[index];
return 0;
}
@@ -55,9 +58,10 @@ static int regcache_flat_read(struct regmap *map,
static int regcache_flat_write(struct regmap *map, unsigned int reg,
unsigned int value)
{
+ unsigned int index = reg / map->reg_stride;
unsigned int *cache = map->cache;
- cache[reg] = value;
+ cache[index] = value;
return 0;
}
--
1.8.3.1
--
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