linux-kernel - [PATCHv2 1/3] regmap: core: Introduce regsiter stride order

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Date:	Mon,  4 Jan 2016 18:00:33 +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: [PATCHv2 1/3] regmap: core: Introduce regsiter stride order

Since the register stride should always equal to 2^N, and bit rotation is
much faster than multiplication and division. So introducing the stride
order and using bit rotation to get the offset of the register from the
index to improve the performance.

Signed-off-by: Xiubo Li <lixiubo@...s.chinamobile.com>
---
 drivers/base/regmap/internal.h | 10 ++++++++++
 drivers/base/regmap/regmap.c   | 19 +++++++++++++------
 2 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/drivers/base/regmap/internal.h b/drivers/base/regmap/internal.h
index 3df9770..c22b04b 100644
--- a/drivers/base/regmap/internal.h
+++ b/drivers/base/regmap/internal.h
@@ -110,6 +110,7 @@ struct regmap {
 	/* number of bits to (left) shift the reg value when formatting*/
 	int reg_shift;
 	int reg_stride;
+	int reg_stride_order;
 
 	/* regcache specific members */
 	const struct regcache_ops *cache_ops;
@@ -263,4 +264,13 @@ static inline const char *regmap_name(const struct regmap *map)
 	return map->name;
 }
 
+static inline unsigned int regmap_get_offset(const struct regmap *map,
+					     unsigned int index)
+{
+	if (map->reg_stride_order >= 0)
+		return index << map->reg_stride_order;
+	else
+		return index * map->reg_stride;
+}
+
 #endif
diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index ee54e84..29d526e 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -19,6 +19,7 @@
 #include <linux/rbtree.h>
 #include <linux/sched.h>
 #include <linux/delay.h>
+#include <linux/log2.h>
 
 #define CREATE_TRACE_POINTS
 #include "trace.h"
@@ -638,6 +639,10 @@ struct regmap *__regmap_init(struct device *dev,
 		map->reg_stride = config->reg_stride;
 	else
 		map->reg_stride = 1;
+	if (is_power_of_2(map->reg_stride))
+		map->reg_stride_order = ilog2(map->reg_stride);
+	else
+		map->reg_stride_order = -1;
 	map->use_single_read = config->use_single_rw || !bus || !bus->read;
 	map->use_single_write = config->use_single_rw || !bus || !bus->write;
 	map->can_multi_write = config->can_multi_write && bus && bus->write;
@@ -1308,7 +1313,7 @@ int _regmap_raw_write(struct regmap *map, unsigned int reg,
 	if (map->writeable_reg)
 		for (i = 0; i < val_len / map->format.val_bytes; i++)
 			if (!map->writeable_reg(map->dev,
-						reg + (i * map->reg_stride)))
+					       reg + regmap_get_offset(map, i)))
 				return -EINVAL;
 
 	if (!map->cache_bypass && map->format.parse_val) {
@@ -1316,7 +1321,8 @@ int _regmap_raw_write(struct regmap *map, unsigned int reg,
 		int val_bytes = map->format.val_bytes;
 		for (i = 0; i < val_len / val_bytes; i++) {
 			ival = map->format.parse_val(val + (i * val_bytes));
-			ret = regcache_write(map, reg + (i * map->reg_stride),
+			ret = regcache_write(map,
+					     reg + regmap_get_offset(map, i),
 					     ival);
 			if (ret) {
 				dev_err(map->dev,
@@ -1846,8 +1852,9 @@ int regmap_bulk_write(struct regmap *map, unsigned int reg, const void *val,
 				goto out;
 			}
 
-			ret = _regmap_write(map, reg + (i * map->reg_stride),
-					ival);
+			ret = _regmap_write(map,
+					    reg + regmap_get_offset(map, i),
+					    ival);
 			if (ret != 0)
 				goto out;
 		}
@@ -2416,7 +2423,7 @@ int regmap_raw_read(struct regmap *map, unsigned int reg, void *val,
 		 * cost as we expect to hit the cache.
 		 */
 		for (i = 0; i < val_count; i++) {
-			ret = _regmap_read(map, reg + (i * map->reg_stride),
+			ret = _regmap_read(map, reg + regmap_get_offset(map, i),
 					   &v);
 			if (ret != 0)
 				goto out;
@@ -2568,7 +2575,7 @@ int regmap_bulk_read(struct regmap *map, unsigned int reg, void *val,
 	} else {
 		for (i = 0; i < val_count; i++) {
 			unsigned int ival;
-			ret = regmap_read(map, reg + (i * map->reg_stride),
+			ret = regmap_read(map, reg + regmap_get_offset(map, i),
 					  &ival);
 			if (ret != 0)
 				return ret;
-- 
1.8.3.1



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