diff --git a/drivers/tty/serial/max310x.c b/drivers/tty/serial/max310x.c
index c0fa4ad10..80298a571 100755
--- a/drivers/tty/serial/max310x.c
+++ b/drivers/tty/serial/max310x.c
@@ -262,6 +262,7 @@ struct max310x_one {
 	struct work_struct	tx_work;
 	struct work_struct	md_work;
 	struct work_struct	rs_work;
+	struct regmap		*regmap;
 
 	u8 rx_buf[MAX310X_FIFO_SIZE];
 };
@@ -291,26 +292,26 @@ static DECLARE_BITMAP(max310x_lines, MAX310X_UART_NRMAX);
 
 static u8 max310x_port_read(struct uart_port *port, u8 reg)
 {
-	struct max310x_port *s = dev_get_drvdata(port->dev);
+	struct max310x_one *one = to_max310x_port(port);
 	unsigned int val = 0;
 
-	regmap_read(s->regmap, port->iobase + reg, &val);
+	regmap_read(one->regmap, reg, &val);
 
 	return val;
 }
 
 static void max310x_port_write(struct uart_port *port, u8 reg, u8 val)
 {
-	struct max310x_port *s = dev_get_drvdata(port->dev);
+	struct max310x_one *one = to_max310x_port(port);
 
-	regmap_write(s->regmap, port->iobase + reg, val);
+	regmap_write(one->regmap, reg, val);
 }
 
 static void max310x_port_update(struct uart_port *port, u8 reg, u8 mask, u8 val)
 {
-	struct max310x_port *s = dev_get_drvdata(port->dev);
+	struct max310x_one *one = to_max310x_port(port);
 
-	regmap_update_bits(s->regmap, port->iobase + reg, mask, val);
+	regmap_update_bits(one->regmap, reg, mask, val);
 }
 
 static int max3107_detect(struct device *dev)
@@ -449,7 +450,7 @@ static const struct max310x_devtype max14830_devtype = {
 
 static bool max310x_reg_writeable(struct device *dev, unsigned int reg)
 {
-	switch (reg & 0x1f) {
+	switch (reg) {
 	case MAX310X_IRQSTS_REG:
 	case MAX310X_LSR_IRQSTS_REG:
 	case MAX310X_SPCHR_IRQSTS_REG:
@@ -466,7 +467,7 @@ static bool max310x_reg_writeable(struct device *dev, unsigned int reg)
 
 static bool max310x_reg_volatile(struct device *dev, unsigned int reg)
 {
-	switch (reg & 0x1f) {
+	switch (reg) {
 	case MAX310X_RHR_REG:
 	case MAX310X_IRQSTS_REG:
 	case MAX310X_LSR_IRQSTS_REG:
@@ -488,7 +489,7 @@ static bool max310x_reg_volatile(struct device *dev, unsigned int reg)
 
 static bool max310x_reg_precious(struct device *dev, unsigned int reg)
 {
-	switch (reg & 0x1f) {
+	switch (reg) {
 	case MAX310X_RHR_REG:
 	case MAX310X_IRQSTS_REG:
 	case MAX310X_SPCHR_IRQSTS_REG:
@@ -633,18 +634,16 @@ static s32 max310x_set_ref_clk(struct device *dev, struct max310x_port *s,
 
 static void max310x_batch_write(struct uart_port *port, u8 *txbuf, unsigned int len)
 {
-	struct max310x_port *s = dev_get_drvdata(port->dev);
-	u8 reg = port->iobase + MAX310X_THR_REG;
+	struct max310x_one *one = to_max310x_port(port);
 
-	regmap_raw_write(s->regmap, reg, txbuf, len);
+	regmap_raw_write(one->regmap, MAX310X_THR_REG, txbuf, len);
 }
 
 static void max310x_batch_read(struct uart_port *port, u8 *rxbuf, unsigned int len)
 {
-	struct max310x_port *s = dev_get_drvdata(port->dev);
-	u8 reg = port->iobase + MAX310X_RHR_REG;
+	struct max310x_one *one = to_max310x_port(port);
 
-	regmap_raw_read(s->regmap, reg, rxbuf, len);
+	regmap_raw_read(one->regmap, MAX310X_RHR_REG, rxbuf, len);
 }
 
 static void max310x_handle_rx(struct uart_port *port, unsigned int rxlen)
@@ -1247,15 +1246,16 @@ static int max310x_gpio_set_config(struct gpio_chip *chip, unsigned int offset,
 #endif
 
 static int max310x_probe(struct device *dev, const struct max310x_devtype *devtype,
-			 struct regmap *regmap, int irq)
+			 struct regmap *regmaps[], int irq)
 {
 	int i, ret, fmin, fmax, freq;
 	struct max310x_port *s;
 	s32 uartclk = 0;
 	bool xtal;
 
-	if (IS_ERR(regmap))
-		return PTR_ERR(regmap);
+	for (i = 0; i < devtype->nr; i++)
+		if (IS_ERR(regmaps[i]))
+			return PTR_ERR(regmaps[i]);
 
 	/* Alloc port structure */
 	s = devm_kzalloc(dev, struct_size(s, p, devtype->nr), GFP_KERNEL);
@@ -1306,7 +1306,7 @@ static int max310x_probe(struct device *dev, const struct max310x_devtype *devty
 		goto out_clk;
 	}
 
-	s->regmap = regmap;
+	s->regmap = regmaps[0];
 	s->devtype = devtype;
 	dev_set_drvdata(dev, s);
 
@@ -1316,22 +1316,18 @@ static int max310x_probe(struct device *dev, const struct max310x_devtype *devty
 		goto out_clk;
 
 	for (i = 0; i < devtype->nr; i++) {
-		unsigned int offs = i << 5;
-
 		/* Reset port */
-		regmap_write(s->regmap, MAX310X_MODE2_REG + offs,
+		regmap_write(regmaps[i], MAX310X_MODE2_REG,
 			     MAX310X_MODE2_RST_BIT);
 		/* Clear port reset */
-		regmap_write(s->regmap, MAX310X_MODE2_REG + offs, 0);
+		regmap_write(regmaps[i], MAX310X_MODE2_REG, 0);
 
 		/* Wait for port startup */
 		do {
-			regmap_read(s->regmap,
-				    MAX310X_BRGDIVLSB_REG + offs, &ret);
+			regmap_read(regmaps[i], MAX310X_BRGDIVLSB_REG, &ret);
 		} while (ret != 0x01);
 
-		regmap_write(s->regmap, MAX310X_MODE1_REG + offs,
-			     devtype->mode1);
+		regmap_write(regmaps[i], MAX310X_MODE1_REG, devtype->mode1);
 	}
 
 	uartclk = max310x_set_ref_clk(dev, s, freq, xtal);
@@ -1359,11 +1355,13 @@ static int max310x_probe(struct device *dev, const struct max310x_devtype *devty
 		s->p[i].port.fifosize	= MAX310X_FIFO_SIZE;
 		s->p[i].port.flags	= UPF_FIXED_TYPE | UPF_LOW_LATENCY;
 		s->p[i].port.iotype	= UPIO_PORT;
-		s->p[i].port.iobase	= i * 0x20;
+		s->p[i].port.iobase	= i;
 		s->p[i].port.membase	= (void __iomem *)~0;
 		s->p[i].port.uartclk	= uartclk;
 		s->p[i].port.rs485_config = max310x_rs485_config;
 		s->p[i].port.ops	= &max310x_ops;
+		s->p[i].regmap		= regmaps[i];
+
 		/* Disable all interrupts */
 		max310x_port_write(&s->p[i].port, MAX310X_IRQEN_REG, 0);
 		/* Clear IRQ status register */
@@ -1460,6 +1458,7 @@ static struct regmap_config regcfg = {
 	.val_bits = 8,
 	.write_flag_mask = MAX310X_WRITE_BIT,
 	.cache_type = REGCACHE_RBTREE,
+	.max_register = MAX310X_REG_1F,
 	.writeable_reg = max310x_reg_writeable,
 	.volatile_reg = max310x_reg_volatile,
 	.precious_reg = max310x_reg_precious,
@@ -1469,7 +1468,8 @@ static struct regmap_config regcfg = {
 static int max310x_spi_probe(struct spi_device *spi)
 {
 	const struct max310x_devtype *devtype;
-	struct regmap *regmap;
+	struct regmap *regmaps[4];
+	unsigned int i;
 	int ret;
 
 	/* Setup SPI bus */
@@ -1484,10 +1484,14 @@ static int max310x_spi_probe(struct spi_device *spi)
 	if (!devtype)
 		devtype = (struct max310x_devtype *)spi_get_device_id(spi)->driver_data;
 
-	regcfg.max_register = devtype->nr * 0x20 - 1;
-	regmap = devm_regmap_init_spi(spi, &regcfg);
+	for (i = 0; i < devtype->nr; i++) {
+		u8 port_mask = i * 0x20;
+		regcfg.read_flag_mask = port_mask;
+		regcfg.write_flag_mask = port_mask | MAX310X_WRITE_BIT;
+		regmaps[i] = devm_regmap_init_spi(spi, &regcfg);
+	}
 
-	return max310x_probe(&spi->dev, devtype, regmap, spi->irq);
+	return max310x_probe(&spi->dev, devtype, regmaps, spi->irq);
 }
 
 static int max310x_spi_remove(struct spi_device *spi)