diff --git a/drivers/iio/addac/Kconfig b/drivers/iio/addac/Kconfig
index 2843fcb70e24..877f9124803c 100644
--- a/drivers/iio/addac/Kconfig
+++ b/drivers/iio/addac/Kconfig
@@ -35,7 +35,9 @@ config STX104
 	tristate "Apex Embedded Systems STX104 driver"
 	depends on PC104 && X86
 	select ISA_BUS_API
+	select REGMAP_MMIO
 	select GPIOLIB
+	select GPIO_REGMAP
 	help
 	  Say yes here to build support for the Apex Embedded Systems STX104
 	  integrated analog PC/104 card.
diff --git a/drivers/iio/addac/stx104.c b/drivers/iio/addac/stx104.c
index e45b70aa5bb7..7e15410d3100 100644
--- a/drivers/iio/addac/stx104.c
+++ b/drivers/iio/addac/stx104.c
@@ -3,19 +3,18 @@
  * IIO driver for the Apex Embedded Systems STX104
  * Copyright (C) 2016 William Breathitt Gray
  */
+#include <linux/bitfield.h>
 #include <linux/bits.h>
 #include <linux/device.h>
-#include <linux/errno.h>
-#include <linux/gpio/driver.h>
+#include <linux/err.h>
+#include <linux/gpio/regmap.h>
 #include <linux/iio/iio.h>
 #include <linux/iio/types.h>
-#include <linux/io.h>
-#include <linux/ioport.h>
 #include <linux/isa.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/moduleparam.h>
-#include <linux/spinlock.h>
+#include <linux/regmap.h>
 #include <linux/types.h>
 
 #define STX104_OUT_CHAN(chan) {				\
@@ -45,101 +44,190 @@ static unsigned int num_stx104;
 module_param_hw_array(base, uint, ioport, &num_stx104, 0);
 MODULE_PARM_DESC(base, "Apex Embedded Systems STX104 base addresses");
 
-/**
- * struct stx104_reg - device register structure
- * @ssr_ad:	Software Strobe Register and ADC Data
- * @achan:	ADC Channel
- * @dio:	Digital I/O
- * @dac:	DAC Channels
- * @cir_asr:	Clear Interrupts and ADC Status
- * @acr:	ADC Control
- * @pccr_fsh:	Pacer Clock Control and FIFO Status MSB
- * @acfg:	ADC Configuration
- */
-struct stx104_reg {
-	u16 ssr_ad;
-	u8 achan;
-	u8 dio;
-	u16 dac[2];
-	u8 cir_asr;
-	u8 acr;
-	u8 pccr_fsh;
-	u8 acfg;
+#define AIO_BASE 0x0
+#define SOFTWARE_STROBE AIO_BASE
+#define ADC_DATA AIO_BASE
+#define ADC_CHANNEL (AIO_BASE + 0x2)
+#define DIO_REG (AIO_BASE + 0x3)
+#define DAC_BASE (AIO_BASE + 0x4)
+#define ADC_STATUS (AIO_BASE + 0x8)
+#define ADC_CONTROL (AIO_BASE + 0x9)
+#define ADC_CONFIGURATION (AIO_BASE + 0x11)
+
+#define AIO_DATA_STRIDE 2
+#define DAC_OFFSET(_channel) (DAC_BASE + AIO_DATA_STRIDE * (_channel))
+
+/* ADC Channel */
+#define FC GENMASK(3, 0)
+#define LC GENMASK(7, 4)
+#define SAME_CHANNEL(_channel) (FIELD_PREP(FC, _channel) | FIELD_PREP(LC, _channel))
+
+/* ADC Status */
+#define SD BIT(5)
+#define CNV BIT(7)
+#define DIFFERENTIAL 1
+
+/* ADC Control */
+#define ALSS GENMASK(1, 0)
+#define SOFTWARE_TRIGGER 0
+
+/* ADC Configuration */
+#define GAIN GENMASK(1, 0)
+#define ADBU BIT(2)
+#define BIPOLAR 0
+#define GAIN_X1 0
+#define GAIN_X2 1
+#define GAIN_X4 2
+#define GAIN_X8 3
+
+static const struct regmap_range aio_ctl_wr_ranges[] = {
+	regmap_reg_range(0x0, 0x0), regmap_reg_range(0x2, 0x2), regmap_reg_range(0x9, 0x9),
+	regmap_reg_range(0x11, 0x11),
+};
+static const struct regmap_range aio_ctl_rd_ranges[] = {
+	regmap_reg_range(0x2, 0x2), regmap_reg_range(0x8, 0x9), regmap_reg_range(0x11, 0x11),
+};
+static const struct regmap_range aio_ctl_volatile_ranges[] = {
+	regmap_reg_range(0x8, 0x8),
+};
+static const struct regmap_access_table aio_ctl_wr_table = {
+	.yes_ranges = aio_ctl_wr_ranges,
+	.n_yes_ranges = ARRAY_SIZE(aio_ctl_wr_ranges),
+};
+static const struct regmap_access_table aio_ctl_rd_table = {
+	.yes_ranges = aio_ctl_rd_ranges,
+	.n_yes_ranges = ARRAY_SIZE(aio_ctl_rd_ranges),
+};
+static const struct regmap_access_table aio_ctl_volatile_table = {
+	.yes_ranges = aio_ctl_volatile_ranges,
+	.n_yes_ranges = ARRAY_SIZE(aio_ctl_volatile_ranges),
 };
 
-/**
- * struct stx104_iio - IIO device private data structure
- * @chan_out_states:	channels' output states
- * @reg:		I/O address offset for the device registers
- */
-struct stx104_iio {
-	unsigned int chan_out_states[STX104_NUM_OUT_CHAN];
-	struct stx104_reg __iomem *reg;
+static const struct regmap_config aio_ctl_regmap_config = {
+	.name = "aio_ctl",
+	.reg_bits = 8,
+	.reg_stride = 1,
+	.val_bits = 8,
+	.io_port = true,
+	.max_register = 0x11,
+	.wr_table = &aio_ctl_wr_table,
+	.rd_table = &aio_ctl_rd_table,
+	.volatile_table = &aio_ctl_volatile_table,
+	.cache_type = REGCACHE_FLAT,
+};
+
+static const struct regmap_range aio_data_wr_ranges[] = {
+	regmap_reg_range(0x4, 0x7),
+};
+static const struct regmap_range aio_data_rd_ranges[] = {
+	regmap_reg_range(0x0, 0x1),
+};
+static const struct regmap_access_table aio_data_wr_table = {
+	.yes_ranges = aio_data_wr_ranges,
+	.n_yes_ranges = ARRAY_SIZE(aio_data_wr_ranges),
+};
+static const struct regmap_access_table aio_data_rd_table = {
+	.yes_ranges = aio_data_rd_ranges,
+	.n_yes_ranges = ARRAY_SIZE(aio_data_rd_ranges),
+};
+
+static const struct regmap_config aio_data_regmap_config = {
+	.name = "aio_data",
+	.reg_bits = 16,
+	.reg_stride = AIO_DATA_STRIDE,
+	.val_bits = 16,
+	.io_port = true,
+	.max_register = 0x7,
+	.wr_table = &aio_data_wr_table,
+	.rd_table = &aio_data_rd_table,
+	.volatile_table = &aio_data_rd_table,
+	.cache_type = REGCACHE_FLAT,
+};
+
+static const struct regmap_config dio_regmap_config = {
+	.name = "dio",
+	.reg_bits = 8,
+	.reg_stride = 1,
+	.val_bits = 8,
+	.io_port = true,
+	.max_register = 0x0,
 };
 
 /**
- * struct stx104_gpio - GPIO device private data structure
- * @chip:	instance of the gpio_chip
- * @lock:	synchronization lock to prevent I/O race conditions
- * @base:	base port address of the GPIO device
- * @out_state:	output bits state
+ * struct stx104_iio - IIO device private data structure
+ * @aio_data_map: Regmap for analog I/O data
+ * @aio_ctl_map: Regmap for analog I/O control
  */
-struct stx104_gpio {
-	struct gpio_chip chip;
-	spinlock_t lock;
-	u8 __iomem *base;
-	unsigned int out_state;
+struct stx104_iio {
+	struct regmap *aio_data_map;
+	struct regmap *aio_ctl_map;
 };
 
 static int stx104_read_raw(struct iio_dev *indio_dev,
 	struct iio_chan_spec const *chan, int *val, int *val2, long mask)
 {
 	struct stx104_iio *const priv = iio_priv(indio_dev);
-	struct stx104_reg __iomem *const reg = priv->reg;
+	int err;
 	unsigned int adc_config;
-	int adbu;
-	int gain;
+	unsigned int value;
+	unsigned int adc_status;
 
 	switch (mask) {
 	case IIO_CHAN_INFO_HARDWAREGAIN:
-		/* get gain configuration */
-		adc_config = ioread8(&reg->acfg);
-		gain = adc_config & 0x3;
+		err = regmap_read(priv->aio_ctl_map, ADC_CONFIGURATION, &adc_config);
+		if (err)
+			return err;
 
-		*val = 1 << gain;
+		*val = 1 << FIELD_GET(GAIN, adc_config);
 		return IIO_VAL_INT;
 	case IIO_CHAN_INFO_RAW:
 		if (chan->output) {
-			*val = priv->chan_out_states[chan->channel];
+			err = regmap_read(priv->aio_data_map, DAC_OFFSET(chan->channel), &value);
+			if (err)
+				return err;
+			*val = value;
 			return IIO_VAL_INT;
 		}
 
 		/* select ADC channel */
-		iowrite8(chan->channel | (chan->channel << 4), &reg->achan);
+		err = regmap_write(priv->aio_ctl_map, ADC_CHANNEL, SAME_CHANNEL(chan->channel));
+		if (err)
+			return err;
 
 		/* trigger ADC sample capture by writing to the 8-bit
 		 * Software Strobe Register and wait for completion
 		 */
-		iowrite8(0, &reg->ssr_ad);
-		while (ioread8(&reg->cir_asr) & BIT(7));
-
-		*val = ioread16(&reg->ssr_ad);
+		err = regmap_write(priv->aio_ctl_map, SOFTWARE_STROBE, 0);
+		if (err)
+			return err;
+		do {
+			err = regmap_read(priv->aio_ctl_map, ADC_STATUS, &adc_status);
+			if (err)
+				return err;
+		} while (FIELD_GET(CNV, adc_status));
+
+		err = regmap_read(priv->aio_data_map, ADC_DATA, &value);
+		if (err)
+			return err;
+		*val = value;
 		return IIO_VAL_INT;
 	case IIO_CHAN_INFO_OFFSET:
 		/* get ADC bipolar/unipolar configuration */
-		adc_config = ioread8(&reg->acfg);
-		adbu = !(adc_config & BIT(2));
+		err = regmap_read(priv->aio_ctl_map, ADC_CONFIGURATION, &adc_config);
+		if (err)
+			return err;
 
-		*val = -32768 * adbu;
+		*val = (FIELD_GET(ADBU, adc_config) == BIPOLAR) ? -32768 : 0;
 		return IIO_VAL_INT;
 	case IIO_CHAN_INFO_SCALE:
 		/* get ADC bipolar/unipolar and gain configuration */
-		adc_config = ioread8(&reg->acfg);
-		adbu = !(adc_config & BIT(2));
-		gain = adc_config & 0x3;
+		err = regmap_read(priv->aio_ctl_map, ADC_CONFIGURATION, &adc_config);
+		if (err)
+			return err;
 
 		*val = 5;
-		*val2 = 15 - adbu + gain;
+		*val2 = (FIELD_GET(ADBU, adc_config) == BIPOLAR) ? 14 : 15;
+		*val2 += FIELD_GET(GAIN, adc_config);
 		return IIO_VAL_FRACTIONAL_LOG2;
 	}
 
@@ -150,38 +238,36 @@ static int stx104_write_raw(struct iio_dev *indio_dev,
 	struct iio_chan_spec const *chan, int val, int val2, long mask)
 {
 	struct stx104_iio *const priv = iio_priv(indio_dev);
+	u8 gain;
 
 	switch (mask) {
 	case IIO_CHAN_INFO_HARDWAREGAIN:
 		/* Only four gain states (x1, x2, x4, x8) */
 		switch (val) {
 		case 1:
-			iowrite8(0, &priv->reg->acfg);
+			gain = GAIN_X1;
 			break;
 		case 2:
-			iowrite8(1, &priv->reg->acfg);
+			gain = GAIN_X2;
 			break;
 		case 4:
-			iowrite8(2, &priv->reg->acfg);
+			gain = GAIN_X4;
 			break;
 		case 8:
-			iowrite8(3, &priv->reg->acfg);
+			gain = GAIN_X8;
 			break;
 		default:
 			return -EINVAL;
 		}
 
-		return 0;
+		return regmap_write(priv->aio_ctl_map, ADC_CONFIGURATION, gain);
 	case IIO_CHAN_INFO_RAW:
 		if (chan->output) {
 			/* DAC can only accept up to a 16-bit value */
 			if ((unsigned int)val > 65535)
 				return -EINVAL;
 
-			priv->chan_out_states[chan->channel] = val;
-			iowrite16(val, &priv->reg->dac[chan->channel]);
-
-			return 0;
+			return regmap_write(priv->aio_data_map, DAC_OFFSET(chan->channel), val);
 		}
 		return -EINVAL;
 	}
@@ -212,119 +298,66 @@ static const struct iio_chan_spec stx104_channels_diff[] = {
 	STX104_IN_CHAN(6, 1), STX104_IN_CHAN(7, 1)
 };
 
-static int stx104_gpio_get_direction(struct gpio_chip *chip,
-	unsigned int offset)
-{
-	/* GPIO 0-3 are input only, while the rest are output only */
-	if (offset < 4)
-		return 1;
-
-	return 0;
-}
-
-static int stx104_gpio_direction_input(struct gpio_chip *chip,
-	unsigned int offset)
-{
-	if (offset >= 4)
-		return -EINVAL;
-
-	return 0;
-}
-
-static int stx104_gpio_direction_output(struct gpio_chip *chip,
-	unsigned int offset, int value)
-{
-	if (offset < 4)
-		return -EINVAL;
-
-	chip->set(chip, offset, value);
-	return 0;
-}
-
-static int stx104_gpio_get(struct gpio_chip *chip, unsigned int offset)
+static int stx104_reg_mask_xlate(struct gpio_regmap *const gpio, const unsigned int base,
+				 unsigned int offset, unsigned int *const reg,
+				 unsigned int *const mask)
 {
-	struct stx104_gpio *const stx104gpio = gpiochip_get_data(chip);
-
+	/* Output lines are located at same register bit offsets as input lines */
 	if (offset >= 4)
-		return -EINVAL;
-
-	return !!(ioread8(stx104gpio->base) & BIT(offset));
-}
-
-static int stx104_gpio_get_multiple(struct gpio_chip *chip, unsigned long *mask,
-	unsigned long *bits)
-{
-	struct stx104_gpio *const stx104gpio = gpiochip_get_data(chip);
+		offset -= 4;
 
-	*bits = ioread8(stx104gpio->base);
+	*reg = base;
+	*mask = BIT(offset);
 
 	return 0;
 }
 
-static void stx104_gpio_set(struct gpio_chip *chip, unsigned int offset,
-	int value)
-{
-	struct stx104_gpio *const stx104gpio = gpiochip_get_data(chip);
-	const unsigned int mask = BIT(offset) >> 4;
-	unsigned long flags;
-
-	if (offset < 4)
-		return;
-
-	spin_lock_irqsave(&stx104gpio->lock, flags);
-
-	if (value)
-		stx104gpio->out_state |= mask;
-	else
-		stx104gpio->out_state &= ~mask;
-
-	iowrite8(stx104gpio->out_state, stx104gpio->base);
-
-	spin_unlock_irqrestore(&stx104gpio->lock, flags);
-}
-
 #define STX104_NGPIO 8
 static const char *stx104_names[STX104_NGPIO] = {
 	"DIN0", "DIN1", "DIN2", "DIN3", "DOUT0", "DOUT1", "DOUT2", "DOUT3"
 };
 
-static void stx104_gpio_set_multiple(struct gpio_chip *chip,
-	unsigned long *mask, unsigned long *bits)
+static int stx104_init_hw(struct stx104_iio *const priv)
 {
-	struct stx104_gpio *const stx104gpio = gpiochip_get_data(chip);
-	unsigned long flags;
-
-	/* verify masked GPIO are output */
-	if (!(*mask & 0xF0))
-		return;
+	int err;
 
-	*mask >>= 4;
-	*bits >>= 4;
+	/* configure device for software trigger operation */
+	err = regmap_write(priv->aio_ctl_map, ADC_CONTROL, SOFTWARE_TRIGGER);
+	if (err)
+		return err;
 
-	spin_lock_irqsave(&stx104gpio->lock, flags);
+	/* initialize gain setting to x1 */
+	err = regmap_write(priv->aio_ctl_map, ADC_CONFIGURATION, GAIN_X1);
+	if (err)
+		return err;
 
-	stx104gpio->out_state &= ~*mask;
-	stx104gpio->out_state |= *mask & *bits;
-	iowrite8(stx104gpio->out_state, stx104gpio->base);
+	/* initialize DAC outputs to 0V */
+	err = regmap_write(priv->aio_data_map, DAC_BASE, 0);
+	if (err)
+		return err;
+	err = regmap_write(priv->aio_data_map, DAC_BASE + AIO_DATA_STRIDE, 0);
+	if (err)
+		return err;
 
-	spin_unlock_irqrestore(&stx104gpio->lock, flags);
+	return 0;
 }
 
 static int stx104_probe(struct device *dev, unsigned int id)
 {
 	struct iio_dev *indio_dev;
 	struct stx104_iio *priv;
-	struct stx104_gpio *stx104gpio;
+	struct gpio_regmap_config gpio_config = {};
+	void __iomem *stx104_base;
+	struct regmap *aio_ctl_map;
+	struct regmap *aio_data_map;
+	struct regmap *dio_map;
 	int err;
+	unsigned int adc_status;
 
 	indio_dev = devm_iio_device_alloc(dev, sizeof(*priv));
 	if (!indio_dev)
 		return -ENOMEM;
 
-	stx104gpio = devm_kzalloc(dev, sizeof(*stx104gpio), GFP_KERNEL);
-	if (!stx104gpio)
-		return -ENOMEM;
-
 	if (!devm_request_region(dev, base[id], STX104_EXTENT,
 		dev_name(dev))) {
 		dev_err(dev, "Unable to lock port addresses (0x%X-0x%X)\n",
@@ -332,16 +365,35 @@ static int stx104_probe(struct device *dev, unsigned int id)
 		return -EBUSY;
 	}
 
-	priv = iio_priv(indio_dev);
-	priv->reg = devm_ioport_map(dev, base[id], STX104_EXTENT);
-	if (!priv->reg)
+	stx104_base = devm_ioport_map(dev, base[id], STX104_EXTENT);
+	if (!stx104_base)
 		return -ENOMEM;
 
+	aio_ctl_map = devm_regmap_init_mmio(dev, stx104_base + AIO_BASE, &aio_ctl_regmap_config);
+	if (IS_ERR(aio_ctl_map))
+		return dev_err_probe(dev, PTR_ERR(aio_ctl_map),
+				     "Unable to initialize aio_ctl register map\n");
+	aio_data_map = devm_regmap_init_mmio(dev, stx104_base + AIO_BASE, &aio_data_regmap_config);
+	if (IS_ERR(aio_data_map))
+		return dev_err_probe(dev, PTR_ERR(aio_data_map),
+				     "Unable to initialize aio_data register map\n");
+	dio_map = devm_regmap_init_mmio(dev, stx104_base + DIO_REG, &dio_regmap_config);
+	if (IS_ERR(dio_map))
+		return dev_err_probe(dev, PTR_ERR(dio_map),
+				     "Unable to initialize dio register map\n");
+
+	priv = iio_priv(indio_dev);
+	priv->aio_ctl_map = aio_ctl_map;
+	priv->aio_data_map = aio_data_map;
+
 	indio_dev->info = &stx104_info;
 	indio_dev->modes = INDIO_DIRECT_MODE;
 
-	/* determine if differential inputs */
-	if (ioread8(&priv->reg->cir_asr) & BIT(5)) {
+	err = regmap_read(aio_ctl_map, ADC_STATUS, &adc_status);
+	if (err)
+		return err;
+
+	if (FIELD_GET(SD, adc_status) == DIFFERENTIAL) {
 		indio_dev->num_channels = ARRAY_SIZE(stx104_channels_diff);
 		indio_dev->channels = stx104_channels_diff;
 	} else {
@@ -351,41 +403,25 @@ static int stx104_probe(struct device *dev, unsigned int id)
 
 	indio_dev->name = dev_name(dev);
 
-	/* configure device for software trigger operation */
-	iowrite8(0, &priv->reg->acr);
+	err = stx104_init_hw(priv);
+	if (err)
+		return err;
 
-	/* initialize gain setting to x1 */
-	iowrite8(0, &priv->reg->acfg);
-
-	/* initialize DAC output to 0V */
-	iowrite16(0, &priv->reg->dac[0]);
-	iowrite16(0, &priv->reg->dac[1]);
-
-	stx104gpio->chip.label = dev_name(dev);
-	stx104gpio->chip.parent = dev;
-	stx104gpio->chip.owner = THIS_MODULE;
-	stx104gpio->chip.base = -1;
-	stx104gpio->chip.ngpio = STX104_NGPIO;
-	stx104gpio->chip.names = stx104_names;
-	stx104gpio->chip.get_direction = stx104_gpio_get_direction;
-	stx104gpio->chip.direction_input = stx104_gpio_direction_input;
-	stx104gpio->chip.direction_output = stx104_gpio_direction_output;
-	stx104gpio->chip.get = stx104_gpio_get;
-	stx104gpio->chip.get_multiple = stx104_gpio_get_multiple;
-	stx104gpio->chip.set = stx104_gpio_set;
-	stx104gpio->chip.set_multiple = stx104_gpio_set_multiple;
-	stx104gpio->base = &priv->reg->dio;
-	stx104gpio->out_state = 0x0;
-
-	spin_lock_init(&stx104gpio->lock);
-
-	err = devm_gpiochip_add_data(dev, &stx104gpio->chip, stx104gpio);
-	if (err) {
-		dev_err(dev, "GPIO registering failed (%d)\n", err);
+	err = devm_iio_device_register(dev, indio_dev);
+	if (err)
 		return err;
-	}
 
-	return devm_iio_device_register(dev, indio_dev);
+	gpio_config.parent = dev;
+	gpio_config.regmap = dio_map;
+	gpio_config.ngpio = STX104_NGPIO;
+	gpio_config.names = stx104_names;
+	gpio_config.reg_dat_base = GPIO_REGMAP_ADDR(DIO_REG);
+	gpio_config.reg_set_base = GPIO_REGMAP_ADDR(DIO_REG);
+	gpio_config.ngpio_per_reg = STX104_NGPIO;
+	gpio_config.reg_mask_xlate = stx104_reg_mask_xlate;
+	gpio_config.drvdata = dio_map;
+
+	return PTR_ERR_OR_ZERO(devm_gpio_regmap_register(dev, &gpio_config));
 }
 
 static struct isa_driver stx104_driver = {
