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.
Signed-off-by: NJon Ringle <jringle@gridpoint.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/base/regmap/internal.h

@@ -98,6 +98,9 @@ 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 *change, bool force_write);
 
 	bool defer_caching;
 

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);
@@ -2509,6 +2510,30 @@ static int _regmap_update_bits(struct regmap *map, unsigned int reg,
 	int ret;
 	unsigned int tmp, orig;
 
+	if (map->reg_update_bits) {
+		ret = map->reg_update_bits(map->bus_context, reg, mask, val,
+					   change, force_write);
+		if (ret != 0)
+			return ret;
+
+		/* Fix up the cache by read/modify/write */
+		if (!map->cache_bypass && !map->defer_caching) {
+			ret = regcache_read(map, reg, &orig);
+			if (ret != 0)
+				return ret;
+
+			tmp = orig & ~mask;
+			tmp |= val & mask;
+
+			ret = regcache_write(map, reg, tmp);
+			if (ret != 0)
+				return ret;
+			if (map->cache_only)
+				map->cache_dirty = true;
+		}
+		return ret;
+	}
+
 	ret = _regmap_read(map, reg, &orig);
 	if (ret != 0)
 		return ret;

include/linux/regmap.h

@@ -296,6 +296,9 @@ typedef int (*regmap_hw_reg_read)(void *context, unsigned int reg,
 				  unsigned int *val);
 typedef int (*regmap_hw_reg_write)(void *context, unsigned int reg,
 				   unsigned int val);
+typedef int (*regmap_hw_reg_update_bits)(void *context, unsigned int reg,
+					 unsigned int mask, unsigned int val,
+					 bool *change, bool force_write);
 typedef struct regmap_async *(*regmap_hw_async_alloc)(void);
 typedef void (*regmap_hw_free_context)(void *context);
 
@@ -335,6 +338,7 @@ struct regmap_bus {
 	regmap_hw_gather_write gather_write;
 	regmap_hw_async_write async_write;
 	regmap_hw_reg_write reg_write;
+	regmap_hw_reg_update_bits reg_update_bits;
 	regmap_hw_read read;
 	regmap_hw_reg_read reg_read;
 	regmap_hw_free_context free_context;