linux-kernel - [PATCH 3/3] regcache: flat: Introduce regcache_get

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Date:	Thu, 17 Dec 2015 16:45:30 +0800
From:	Xiubo Li <lixiubo@...s.chinamobile.com>
To:	broonie@...nel.org
Cc:	linux-kernel@...r.kernel.org,
	Xiubo Li <lixiubo@...s.chinamobile.com>
Subject: [PATCH 3/3] regcache: flat: Introduce regcache_get_index()

Here we introduce regcache_get_index(), which using register stride
order and bit rotation, will save some memory spaces for flat cache.
Though this will also lost some access performance, since the bit
rotation is used to get the index of the cache array, and this could
be ingored for memory I/O accessing.

Signed-off-by: Xiubo Li <lixiubo@...s.chinamobile.com>
---
 drivers/base/regmap/regcache-flat.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/base/regmap/regcache-flat.c b/drivers/base/regmap/regcache-flat.c
index 686c9e0..218cf39 100644
--- a/drivers/base/regmap/regcache-flat.c
+++ b/drivers/base/regmap/regcache-flat.c
@@ -21,15 +21,16 @@ static int regcache_flat_init(struct regmap *map)
 	int i;
 	unsigned int *cache;
 
-	map->cache = kcalloc(map->max_register + 1, sizeof(unsigned int),
-			     GFP_KERNEL);
+	map->cache = kcalloc(regcache_get_index(map, map->max_register) + 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;
+		cache[regcache_get_index(map, map->reg_defaults[i].reg)] =
+				map->reg_defaults[i].def;
 
 	return 0;
 }
@@ -47,7 +48,7 @@ static int regcache_flat_read(struct regmap *map,
 {
 	unsigned int *cache = map->cache;
 
-	*value = cache[reg];
+	*value = cache[regcache_get_index(map, reg)];
 
 	return 0;
 }
@@ -57,7 +58,7 @@ static int regcache_flat_write(struct regmap *map, unsigned int reg,
 {
 	unsigned int *cache = map->cache;
 
-	cache[reg] = value;
+	cache[regcache_get_index(map, reg)] = value;
 
 	return 0;
 }
-- 
1.8.3.1



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