regmap: Allow installing custom reg_update_bits function

This commit allows installing a custom reg_update_bits function for cases where
the hardware provides a mechanism to set or clear register bits without a
read/modify/write cycle. Such is the case with the Microchip ENCX24J600.

If a custom reg_update_bits function is provided, it will only be used against
volatile registers.

Signed-off-by: Jon Ringle <jringle@gridpoint.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

2 files changed, 20 insertions, 11 deletions

diff --git a/drivers/base/regmap/internal.h b/drivers/base/regmap/internal.h
index cc557886ab23..628ad7ac078b 100644
--- a/drivers/base/regmap/internal.h
+++ b/drivers/base/regmap/internal.h
@@ -98,6 +98,8 @@ struct regmap {
 
         int (*reg_read)(void *context, unsigned int reg, unsigned int *val);
         int (*reg_write)(void *context, unsigned int reg, unsigned int val);
+        int (*reg_update_bits)(void *context, unsigned int reg,
+                               unsigned int mask, unsigned int val);
 
         bool defer_caching;
 
diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index afaf56200674..8cd155af3d63 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -619,6 +619,7 @@ struct regmap *__regmap_init(struct device *dev,
                 goto skip_format_initialization;
         } else {
                 map->reg_read  = _regmap_bus_read;
+                map->reg_update_bits = bus->reg_update_bits;
         }
 
         reg_endian = regmap_get_reg_endian(bus, config);
@@ -2509,20 +2510,26 @@ static int _regmap_update_bits(struct regmap *map, unsigned int reg,
         int ret;
         unsigned int tmp, orig;
 
-        ret = _regmap_read(map, reg, &orig);
-        if (ret != 0)
-                return ret;
+        if (change)
+                *change = false;
 
-        tmp = orig & ~mask;
-        tmp |= val & mask;
-
-        if (force_write || (tmp != orig)) {
-                ret = _regmap_write(map, reg, tmp);
-                if (change)
+        if (regmap_volatile(map, reg) && map->reg_update_bits) {
+                ret = map->reg_update_bits(map->bus_context, reg, mask, val);
+                if (ret == 0 && change)
                         *change = true;
         } else {
-                if (change)
-                        *change = false;
+                ret = _regmap_read(map, reg, &orig);
+                if (ret != 0)
+                        return ret;
+
+                tmp = orig & ~mask;
+                tmp |= val & mask;
+
+                if (force_write || (tmp != orig)) {
+                        ret = _regmap_write(map, reg, tmp);
+                        if (ret == 0 && change)
+                                *change = true;
+                }
         }
 
         return ret;