diff --git a/drivers/base/regmap/regcache-rbtree.c b/drivers/base/regmap/regcache-rbtree.c
index 930cad4e5df8a10d7af43c42e2b3d0ebee3bf121..6a7e4fa12854c8ac365edbe6dbf918c04d2ccd59 100644
--- a/drivers/base/regmap/regcache-rbtree.c
+++ b/drivers/base/regmap/regcache-rbtree.c
@@ -23,16 +23,16 @@ static int regcache_rbtree_write(struct regmap *map, unsigned int reg,
 static int regcache_rbtree_exit(struct regmap *map);
 
 struct regcache_rbtree_node {
-	/* the actual rbtree node holding this block */
-	struct rb_node node;
-	/* base register handled by this block */
-	unsigned int base_reg;
 	/* block of adjacent registers */
 	void *block;
 	/* Which registers are present */
 	long *cache_present;
+	/* base register handled by this block */
+	unsigned int base_reg;
 	/* number of registers available in the block */
 	unsigned int blklen;
+	/* the actual rbtree node holding this block */
+	struct rb_node node;
 } __attribute__ ((packed));
 
 struct regcache_rbtree_ctx {
diff --git a/drivers/base/regmap/regmap-i2c.c b/drivers/base/regmap/regmap-i2c.c
index ebd189529760369df33ab021326763b7866c997d..ca193d1ef47cb055f3257a8c8c0b2ba9687a6f5b 100644
--- a/drivers/base/regmap/regmap-i2c.c
+++ b/drivers/base/regmap/regmap-i2c.c
@@ -14,6 +14,79 @@
 #include <linux/i2c.h>
 #include <linux/module.h>
 
+
+static int regmap_smbus_byte_reg_read(void *context, unsigned int reg,
+				      unsigned int *val)
+{
+	struct device *dev = context;
+	struct i2c_client *i2c = to_i2c_client(dev);
+	int ret;
+
+	if (reg > 0xff)
+		return -EINVAL;
+
+	ret = i2c_smbus_read_byte_data(i2c, reg);
+	if (ret < 0)
+		return ret;
+
+	*val = ret;
+
+	return 0;
+}
+
+static int regmap_smbus_byte_reg_write(void *context, unsigned int reg,
+				       unsigned int val)
+{
+	struct device *dev = context;
+	struct i2c_client *i2c = to_i2c_client(dev);
+
+	if (val > 0xff || reg > 0xff)
+		return -EINVAL;
+
+	return i2c_smbus_write_byte_data(i2c, reg, val);
+}
+
+static struct regmap_bus regmap_smbus_byte = {
+	.reg_write = regmap_smbus_byte_reg_write,
+	.reg_read = regmap_smbus_byte_reg_read,
+};
+
+static int regmap_smbus_word_reg_read(void *context, unsigned int reg,
+				      unsigned int *val)
+{
+	struct device *dev = context;
+	struct i2c_client *i2c = to_i2c_client(dev);
+	int ret;
+
+	if (reg > 0xff)
+		return -EINVAL;
+
+	ret = i2c_smbus_read_word_data(i2c, reg);
+	if (ret < 0)
+		return ret;
+
+	*val = ret;
+
+	return 0;
+}
+
+static int regmap_smbus_word_reg_write(void *context, unsigned int reg,
+				       unsigned int val)
+{
+	struct device *dev = context;
+	struct i2c_client *i2c = to_i2c_client(dev);
+
+	if (val > 0xffff || reg > 0xff)
+		return -EINVAL;
+
+	return i2c_smbus_write_word_data(i2c, reg, val);
+}
+
+static struct regmap_bus regmap_smbus_word = {
+	.reg_write = regmap_smbus_word_reg_write,
+	.reg_read = regmap_smbus_word_reg_read,
+};
+
 static int regmap_i2c_write(void *context, const void *data, size_t count)
 {
 	struct device *dev = context;
@@ -97,6 +170,23 @@ static struct regmap_bus regmap_i2c = {
 	.read = regmap_i2c_read,
 };
 
+static const struct regmap_bus *regmap_get_i2c_bus(struct i2c_client *i2c,
+					const struct regmap_config *config)
+{
+	if (i2c_check_functionality(i2c->adapter, I2C_FUNC_I2C))
+		return &regmap_i2c;
+	else if (config->val_bits == 16 && config->reg_bits == 8 &&
+		 i2c_check_functionality(i2c->adapter,
+					 I2C_FUNC_SMBUS_WORD_DATA))
+		return &regmap_smbus_word;
+	else if (config->val_bits == 8 && config->reg_bits == 8 &&
+		 i2c_check_functionality(i2c->adapter,
+					 I2C_FUNC_SMBUS_BYTE_DATA))
+		return &regmap_smbus_byte;
+
+	return ERR_PTR(-ENOTSUPP);
+}
+
 /**
  * regmap_init_i2c(): Initialise register map
  *
@@ -109,7 +199,12 @@ static struct regmap_bus regmap_i2c = {
 struct regmap *regmap_init_i2c(struct i2c_client *i2c,
 			       const struct regmap_config *config)
 {
-	return regmap_init(&i2c->dev, &regmap_i2c, &i2c->dev, config);
+	const struct regmap_bus *bus = regmap_get_i2c_bus(i2c, config);
+
+	if (IS_ERR(bus))
+		return ERR_CAST(bus);
+
+	return regmap_init(&i2c->dev, bus, &i2c->dev, config);
 }
 EXPORT_SYMBOL_GPL(regmap_init_i2c);
 
@@ -126,7 +221,12 @@ EXPORT_SYMBOL_GPL(regmap_init_i2c);
 struct regmap *devm_regmap_init_i2c(struct i2c_client *i2c,
 				    const struct regmap_config *config)
 {
-	return devm_regmap_init(&i2c->dev, &regmap_i2c, &i2c->dev, config);
+	const struct regmap_bus *bus = regmap_get_i2c_bus(i2c, config);
+
+	if (IS_ERR(bus))
+		return ERR_CAST(bus);
+
+	return devm_regmap_init(&i2c->dev, bus, &i2c->dev, config);
 }
 EXPORT_SYMBOL_GPL(devm_regmap_init_i2c);
 
diff --git a/drivers/base/regmap/regmap-irq.c b/drivers/base/regmap/regmap-irq.c
index edf88f20cbce8df434058b18f772393e781b4547..6299a50a59607f6d5598eac804817cef47e8c106 100644
--- a/drivers/base/regmap/regmap-irq.c
+++ b/drivers/base/regmap/regmap-irq.c
@@ -10,13 +10,13 @@
  * published by the Free Software Foundation.
  */
 
-#include <linux/export.h>
 #include <linux/device.h>
-#include <linux/regmap.h>
-#include <linux/irq.h>
+#include <linux/export.h>
 #include <linux/interrupt.h>
+#include <linux/irq.h>
 #include <linux/irqdomain.h>
 #include <linux/pm_runtime.h>
+#include <linux/regmap.h>
 #include <linux/slab.h>
 
 #include "internal.h"
@@ -347,6 +347,9 @@ int regmap_add_irq_chip(struct regmap *map, int irq, int irq_flags,
 	int ret = -ENOMEM;
 	u32 reg;
 
+	if (chip->num_regs <= 0)
+		return -EINVAL;
+
 	for (i = 0; i < chip->num_irqs; i++) {
 		if (chip->irqs[i].reg_offset % map->reg_stride)
 			return -EINVAL;
diff --git a/drivers/base/regmap/regmap-mmio.c b/drivers/base/regmap/regmap-mmio.c
index 1e03e7f8bacb220a47d0edf29700f6a1814fc21e..04a329a377e96b585dd074e2e16340d954e908a4 100644
--- a/drivers/base/regmap/regmap-mmio.c
+++ b/drivers/base/regmap/regmap-mmio.c
@@ -61,9 +61,28 @@ static int regmap_mmio_regbits_check(size_t reg_bits)
 	}
 }
 
-static inline void regmap_mmio_count_check(size_t count)
+static inline void regmap_mmio_count_check(size_t count, u32 offset)
 {
-	BUG_ON(count % 2 != 0);
+	BUG_ON(count <= offset);
+}
+
+static inline unsigned int
+regmap_mmio_get_offset(const void *reg, size_t reg_size)
+{
+	switch (reg_size) {
+	case 1:
+		return *(u8 *)reg;
+	case 2:
+		return *(u16 *)reg;
+	case 4:
+		return *(u32 *)reg;
+#ifdef CONFIG_64BIT
+	case 8:
+		return *(u64 *)reg;
+#endif
+	default:
+		BUG();
+	}
 }
 
 static int regmap_mmio_gather_write(void *context,
@@ -71,7 +90,7 @@ static int regmap_mmio_gather_write(void *context,
 				    const void *val, size_t val_size)
 {
 	struct regmap_mmio_context *ctx = context;
-	u32 offset;
+	unsigned int offset;
 	int ret;
 
 	regmap_mmio_regsize_check(reg_size);
@@ -82,7 +101,7 @@ static int regmap_mmio_gather_write(void *context,
 			return ret;
 	}
 
-	offset = *(u32 *)reg;
+	offset = regmap_mmio_get_offset(reg, reg_size);
 
 	while (val_size) {
 		switch (ctx->val_bytes) {
@@ -118,9 +137,9 @@ static int regmap_mmio_gather_write(void *context,
 static int regmap_mmio_write(void *context, const void *data, size_t count)
 {
 	struct regmap_mmio_context *ctx = context;
-	u32 offset = ctx->reg_bytes + ctx->pad_bytes;
+	unsigned int offset = ctx->reg_bytes + ctx->pad_bytes;
 
-	regmap_mmio_count_check(count);
+	regmap_mmio_count_check(count, offset);
 
 	return regmap_mmio_gather_write(context, data, ctx->reg_bytes,
 					data + offset, count - offset);
@@ -131,7 +150,7 @@ static int regmap_mmio_read(void *context,
 			    void *val, size_t val_size)
 {
 	struct regmap_mmio_context *ctx = context;
-	u32 offset;
+	unsigned int offset;
 	int ret;
 
 	regmap_mmio_regsize_check(reg_size);
@@ -142,7 +161,7 @@ static int regmap_mmio_read(void *context,
 			return ret;
 	}
 
-	offset = *(u32 *)reg;
+	offset = regmap_mmio_get_offset(reg, reg_size);
 
 	while (val_size) {
 		switch (ctx->val_bytes) {
diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index 63e30ef096e2be5e16a1e989bba22dd3b6c69f8d..74d8c0672cf6162e9d3d28afbd68f742a5ecb732 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -35,10 +35,14 @@ static int _regmap_update_bits(struct regmap *map, unsigned int reg,
 			       unsigned int mask, unsigned int val,
 			       bool *change);
 
+static int _regmap_bus_reg_read(void *context, unsigned int reg,
+				unsigned int *val);
 static int _regmap_bus_read(void *context, unsigned int reg,
 			    unsigned int *val);
 static int _regmap_bus_formatted_write(void *context, unsigned int reg,
 				       unsigned int val);
+static int _regmap_bus_reg_write(void *context, unsigned int reg,
+				 unsigned int val);
 static int _regmap_bus_raw_write(void *context, unsigned int reg,
 				 unsigned int val);
 
@@ -192,6 +196,13 @@ static void regmap_format_16_be(void *buf, unsigned int val, unsigned int shift)
 	b[0] = cpu_to_be16(val << shift);
 }
 
+static void regmap_format_16_le(void *buf, unsigned int val, unsigned int shift)
+{
+	__le16 *b = buf;
+
+	b[0] = cpu_to_le16(val << shift);
+}
+
 static void regmap_format_16_native(void *buf, unsigned int val,
 				    unsigned int shift)
 {
@@ -216,6 +227,13 @@ static void regmap_format_32_be(void *buf, unsigned int val, unsigned int shift)
 	b[0] = cpu_to_be32(val << shift);
 }
 
+static void regmap_format_32_le(void *buf, unsigned int val, unsigned int shift)
+{
+	__le32 *b = buf;
+
+	b[0] = cpu_to_le32(val << shift);
+}
+
 static void regmap_format_32_native(void *buf, unsigned int val,
 				    unsigned int shift)
 {
@@ -240,6 +258,13 @@ static unsigned int regmap_parse_16_be(const void *buf)
 	return be16_to_cpu(b[0]);
 }
 
+static unsigned int regmap_parse_16_le(const void *buf)
+{
+	const __le16 *b = buf;
+
+	return le16_to_cpu(b[0]);
+}
+
 static void regmap_parse_16_be_inplace(void *buf)
 {
 	__be16 *b = buf;
@@ -247,6 +272,13 @@ static void regmap_parse_16_be_inplace(void *buf)
 	b[0] = be16_to_cpu(b[0]);
 }
 
+static void regmap_parse_16_le_inplace(void *buf)
+{
+	__le16 *b = buf;
+
+	b[0] = le16_to_cpu(b[0]);
+}
+
 static unsigned int regmap_parse_16_native(const void *buf)
 {
 	return *(u16 *)buf;
@@ -269,6 +301,13 @@ static unsigned int regmap_parse_32_be(const void *buf)
 	return be32_to_cpu(b[0]);
 }
 
+static unsigned int regmap_parse_32_le(const void *buf)
+{
+	const __le32 *b = buf;
+
+	return le32_to_cpu(b[0]);
+}
+
 static void regmap_parse_32_be_inplace(void *buf)
 {
 	__be32 *b = buf;
@@ -276,6 +315,13 @@ static void regmap_parse_32_be_inplace(void *buf)
 	b[0] = be32_to_cpu(b[0]);
 }
 
+static void regmap_parse_32_le_inplace(void *buf)
+{
+	__le32 *b = buf;
+
+	b[0] = le32_to_cpu(b[0]);
+}
+
 static unsigned int regmap_parse_32_native(const void *buf)
 {
 	return *(u32 *)buf;
@@ -493,6 +539,12 @@ struct regmap *regmap_init(struct device *dev,
 		map->reg_read  = config->reg_read;
 		map->reg_write = config->reg_write;
 
+		map->defer_caching = false;
+		goto skip_format_initialization;
+	} else if (!bus->read || !bus->write) {
+		map->reg_read = _regmap_bus_reg_read;
+		map->reg_write = _regmap_bus_reg_write;
+
 		map->defer_caching = false;
 		goto skip_format_initialization;
 	} else {
@@ -608,6 +660,11 @@ struct regmap *regmap_init(struct device *dev,
 			map->format.parse_val = regmap_parse_16_be;
 			map->format.parse_inplace = regmap_parse_16_be_inplace;
 			break;
+		case REGMAP_ENDIAN_LITTLE:
+			map->format.format_val = regmap_format_16_le;
+			map->format.parse_val = regmap_parse_16_le;
+			map->format.parse_inplace = regmap_parse_16_le_inplace;
+			break;
 		case REGMAP_ENDIAN_NATIVE:
 			map->format.format_val = regmap_format_16_native;
 			map->format.parse_val = regmap_parse_16_native;
@@ -629,6 +686,11 @@ struct regmap *regmap_init(struct device *dev,
 			map->format.parse_val = regmap_parse_32_be;
 			map->format.parse_inplace = regmap_parse_32_be_inplace;
 			break;
+		case REGMAP_ENDIAN_LITTLE:
+			map->format.format_val = regmap_format_32_le;
+			map->format.parse_val = regmap_parse_32_le;
+			map->format.parse_inplace = regmap_parse_32_le_inplace;
+			break;
 		case REGMAP_ENDIAN_NATIVE:
 			map->format.format_val = regmap_format_32_native;
 			map->format.parse_val = regmap_parse_32_native;
@@ -1284,6 +1346,14 @@ static int _regmap_bus_formatted_write(void *context, unsigned int reg,
 	return ret;
 }
 
+static int _regmap_bus_reg_write(void *context, unsigned int reg,
+				 unsigned int val)
+{
+	struct regmap *map = context;
+
+	return map->bus->reg_write(map->bus_context, reg, val);
+}
+
 static int _regmap_bus_raw_write(void *context, unsigned int reg,
 				 unsigned int val)
 {
@@ -1615,6 +1685,9 @@ static int _regmap_raw_multi_reg_write(struct regmap *map,
 	size_t pair_size = reg_bytes + pad_bytes + val_bytes;
 	size_t len = pair_size * num_regs;
 
+	if (!len)
+		return -EINVAL;
+
 	buf = kzalloc(len, GFP_KERNEL);
 	if (!buf)
 		return -ENOMEM;
@@ -1662,7 +1735,7 @@ static int _regmap_range_multi_paged_reg_write(struct regmap *map,
 	int ret;
 	int i, n;
 	struct reg_default *base;
-	unsigned int this_page;
+	unsigned int this_page = 0;
 	/*
 	 * the set of registers are not neccessarily in order, but
 	 * since the order of write must be preserved this algorithm
@@ -1925,6 +1998,14 @@ static int _regmap_raw_read(struct regmap *map, unsigned int reg, void *val,
 	return ret;
 }
 
+static int _regmap_bus_reg_read(void *context, unsigned int reg,
+				unsigned int *val)
+{
+	struct regmap *map = context;
+
+	return map->bus->reg_read(map->bus_context, reg, val);
+}
+
 static int _regmap_bus_read(void *context, unsigned int reg,
 			    unsigned int *val)
 {
diff --git a/include/linux/regmap.h b/include/linux/regmap.h
index 85691b9b4fa76a778db7f338874849c27d99d74c..7b0e4b425cdf3e66fb5163ae4557adc8c6a89f63 100644
--- a/include/linux/regmap.h
+++ b/include/linux/regmap.h
@@ -276,6 +276,10 @@ typedef int (*regmap_hw_async_write)(void *context,
 typedef int (*regmap_hw_read)(void *context,
 			      const void *reg_buf, size_t reg_size,
 			      void *val_buf, size_t val_size);
+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 struct regmap_async *(*regmap_hw_async_alloc)(void);
 typedef void (*regmap_hw_free_context)(void *context);
 
@@ -309,7 +313,9 @@ struct regmap_bus {
 	regmap_hw_write write;
 	regmap_hw_gather_write gather_write;
 	regmap_hw_async_write async_write;
+	regmap_hw_reg_write reg_write;
 	regmap_hw_read read;
+	regmap_hw_reg_read reg_read;
 	regmap_hw_free_context free_context;
 	regmap_hw_async_alloc async_alloc;
 	u8 read_flag_mask;