regmap: implement register striding

regmap_config.reg_stride is introduced. All extant register addresses
are a multiple of this value. Users of serial-oriented regmap busses will
typically set this to 1. Users of the MMIO regmap bus will typically set
this based on the value size of their registers, in bytes, so 4 for a
32-bit register.

Throughout the regmap code, actual register addresses are used. Wherever
the register address is used to index some array of values, the address
is divided by the stride to determine the index, or vice-versa. Error-
checking is added to all entry-points for register address data to ensure
that register addresses actually satisfy the specified stride. The MMIO
bus ensures that the specified stride is large enough for the register
size.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

1 files changed, 11 insertions, 3 deletions

diff --git a/drivers/base/regmap/regcache.c b/drivers/base/regmap/regcache.c
index d4368e8b6f9d..835883bda977 100644
--- a/drivers/base/regmap/regcache.c
+++ b/drivers/base/regmap/regcache.c
@@ -59,7 +59,7 @@ static int regcache_hw_init(struct regmap *map)
 	for (count = 0, i = 0; i < map->num_reg_defaults_raw; i++) {
 		val = regcache_get_val(map->reg_defaults_raw,
 				       i, map->cache_word_size);
-		if (regmap_volatile(map, i))
+		if (regmap_volatile(map, i * map->reg_stride))
 			continue;
 		count++;
 	}
@@ -76,9 +76,9 @@ static int regcache_hw_init(struct regmap *map)
 	for (i = 0, j = 0; i < map->num_reg_defaults_raw; i++) {
 		val = regcache_get_val(map->reg_defaults_raw,
 				       i, map->cache_word_size);
-		if (regmap_volatile(map, i))
+		if (regmap_volatile(map, i * map->reg_stride))
 			continue;
-		map->reg_defaults[j].reg = i;
+		map->reg_defaults[j].reg = i * map->reg_stride;
 		map->reg_defaults[j].def = val;
 		j++;
 	}
@@ -98,6 +98,10 @@ int regcache_init(struct regmap *map, const struct regmap_config *config)
 	int i;
 	void *tmp_buf;
 
+	for (i = 0; i < config->num_reg_defaults; i++)
+		if (config->reg_defaults[i].reg % map->reg_stride)
+			return -EINVAL;
+
 	if (map->cache_type == REGCACHE_NONE) {
 		map->cache_bypass = true;
 		return 0;
@@ -278,6 +282,10 @@ int regcache_sync(struct regmap *map)
 	/* Apply any patch first */
 	map->cache_bypass = 1;
 	for (i = 0; i < map->patch_regs; i++) {
+		if (map->patch[i].reg % map->reg_stride) {
+			ret = -EINVAL;
+			goto out;
+		}
 		ret = _regmap_write(map, map->patch[i].reg, map->patch[i].def);
 		if (ret != 0) {
 			dev_err(map->dev, "Failed to write %x = %x: %d\n",