[PATCH v3 2/4] iio: adc: add STMPE ADC driver using IIO framework

[Philippe Schenker]

From: Stefan Agner <stefan@xxxxxxxx>

This adds an ADC driver for the STMPE device using the industrial
input/output interface. The driver supports raw reading of values.
The driver depends on the MFD STMPE driver. If the touchscreen
block is enabled too, only four of the 8 ADC channels are available.

Signed-off-by: Stefan Agner <stefan@xxxxxxxx>
Signed-off-by: Max Krummenacher <max.krummenacher@xxxxxxxxxxx>
Signed-off-by: Philippe Schenker <philippe.schenker@xxxxxxxxxxx>
---

Changes in v3:
 - Undo ADC-settings related code-deletions in stmpe-ts.c that the code is
   backwards-compatible to older devicetrees.

Changes in v2:
 - Code formatting
 - Move code to setup ADC to MFD device, as it is used by both drivers
   adc and touchscreen
 - Removed unused includes
 - Defined the macro STMPE_START_ONE_TEMP_CONV with other macros.
 - Added new macro that defines the channel of the temperature sensor.
   Took new name for STMPE_MAX_ADC->STMPE_ADC_LAST_NR and used it throughout
   the code for better readability.
 - Added mutex_unlock where missing.

 drivers/iio/adc/Kconfig              |   7 +
 drivers/iio/adc/Makefile             |   1 +
 drivers/iio/adc/stmpe-adc.c          | 326 +++++++++++++++++++++++++++
 drivers/input/touchscreen/stmpe-ts.c |  36 +--
 drivers/mfd/Kconfig                  |   3 +-
 drivers/mfd/stmpe.c                  |  81 +++++++
 include/linux/mfd/stmpe.h            |   9 +
 7 files changed, 437 insertions(+), 26 deletions(-)
 create mode 100644 drivers/iio/adc/stmpe-adc.c

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index a52fea8749a9..224f2067494d 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -734,6 +734,13 @@ config STM32_DFSDM_ADC
 	  This driver can also be built as a module.  If so, the module
 	  will be called stm32-dfsdm-adc.
 
+config STMPE_ADC
+	tristate "STMicroelectronics STMPE ADC driver"
+	depends on OF && MFD_STMPE
+	help
+	  Say yes here to build support for ST Microelectronics STMPE
+	  built-in ADC block (stmpe811).
+
 config STX104
 	tristate "Apex Embedded Systems STX104 driver"
 	depends on PC104 && X86
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index a6e6a0b659e2..cba889c30bf9 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -69,6 +69,7 @@ obj-$(CONFIG_STM32_ADC_CORE) += stm32-adc-core.o
 obj-$(CONFIG_STM32_ADC) += stm32-adc.o
 obj-$(CONFIG_STM32_DFSDM_CORE) += stm32-dfsdm-core.o
 obj-$(CONFIG_STM32_DFSDM_ADC) += stm32-dfsdm-adc.o
+obj-$(CONFIG_STMPE_ADC) += stmpe-adc.o
 obj-$(CONFIG_TI_ADC081C) += ti-adc081c.o
 obj-$(CONFIG_TI_ADC0832) += ti-adc0832.o
 obj-$(CONFIG_TI_ADC084S021) += ti-adc084s021.o
diff --git a/drivers/iio/adc/stmpe-adc.c b/drivers/iio/adc/stmpe-adc.c
new file mode 100644
index 000000000000..bea3f3c27bb5
--- /dev/null
+++ b/drivers/iio/adc/stmpe-adc.c
@@ -0,0 +1,326 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  STMicroelectronics STMPE811 IIO ADC Driver
+ *
+ *  4 channel, 10/12-bit ADC
+ *
+ *  Copyright (C) 2013-2018 Toradex AG <stefan.agner@xxxxxxxxxxx>
+ */
+
+#include <linux/completion.h>
+#include <linux/err.h>
+#include <linux/iio/iio.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/mfd/stmpe.h>
+#include <linux/module.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+
+#define STMPE_REG_INT_STA		0x0B
+#define STMPE_REG_ADC_INT_EN		0x0E
+#define STMPE_REG_ADC_INT_STA		0x0F
+
+#define STMPE_REG_ADC_CTRL1		0x20
+#define STMPE_REG_ADC_CTRL2		0x21
+#define STMPE_REG_ADC_CAPT		0x22
+#define STMPE_REG_ADC_DATA_CH(channel)	(0x30 + 2 * (channel))
+
+#define STMPE_REG_TEMP_CTRL		0x60
+#define STMPE_TEMP_CTRL_ENABLE		BIT(0)
+#define STMPE_TEMP_CTRL_ACQ		BIT(1)
+#define STMPE_TEMP_CTRL_THRES_EN	BIT(3)
+#define STMPE_START_ONE_TEMP_CONV	(STMPE_TEMP_CTRL_ENABLE | \
+					STMPE_TEMP_CTRL_ACQ | \
+					STMPE_TEMP_CTRL_THRES_EN)
+#define STMPE_REG_TEMP_DATA		0x61
+#define STMPE_REG_TEMP_TH		0x63
+#define STMPE_ADC_LAST_NR		7
+#define STMPE_TEMP_CHANNEL		(STMPE_ADC_LAST_NR + 1)
+
+#define STMPE_ADC_CH(channel)		((1 << (channel)) & 0xff)
+
+#define STMPE_ADC_TIMEOUT		msecs_to_jiffies(1000)
+
+struct stmpe_adc {
+	struct stmpe *stmpe;
+	struct clk *clk;
+	struct device *dev;
+
+	/* We are allocating plus one for the temperature channel */
+	struct iio_chan_spec stmpe_adc_iio_channels[STMPE_ADC_LAST_NR + 2];
+
+	struct completion completion;
+
+	u8 channel;
+	u32 value;
+};
+
+static int stmpe_read_raw(struct iio_dev *indio_dev,
+			  struct iio_chan_spec const *chan,
+			  int *val,
+			  int *val2,
+			  long mask)
+{
+	struct stmpe_adc *info = iio_priv(indio_dev);
+	long ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+	case IIO_CHAN_INFO_PROCESSED:
+
+		mutex_lock(&indio_dev->mlock);
+
+		info->channel = (u8)chan->channel;
+
+		switch (chan->type) {
+		case IIO_VOLTAGE:
+			if (info->channel > STMPE_ADC_LAST_NR) {
+				mutex_unlock(&indio_dev->mlock);
+				return -EINVAL;
+			}
+
+			stmpe_reg_write(info->stmpe, STMPE_REG_ADC_INT_EN,
+					STMPE_ADC_CH(info->channel));
+
+			stmpe_reg_write(info->stmpe, STMPE_REG_ADC_CAPT,
+					STMPE_ADC_CH(info->channel));
+
+			*val = info->value;
+			break;
+
+		case IIO_TEMP:
+			if (info->channel != STMPE_TEMP_CHANNEL) {
+				mutex_unlock(&indio_dev->mlock);
+				return -EINVAL;
+			}
+
+			stmpe_reg_write(info->stmpe, STMPE_REG_TEMP_CTRL,
+					STMPE_START_ONE_TEMP_CONV);
+			break;
+		default:
+			mutex_unlock(&indio_dev->mlock);
+			return -EINVAL;
+		}
+
+		ret = wait_for_completion_interruptible_timeout
+			(&info->completion, STMPE_ADC_TIMEOUT);
+
+		if (ret <= 0) {
+			mutex_unlock(&indio_dev->mlock);
+			if (ret == 0)
+				return -ETIMEDOUT;
+			else
+				return ret;
+		}
+
+		switch (chan->type) {
+		case IIO_VOLTAGE:
+			*val = info->value;
+			break;
+
+		case IIO_TEMP:
+			/*
+			 * absolute temp = +V3.3 * value /7.51 [K]
+			 * scale to [milli ÂC]
+			 */
+			*val = ((449960l * info->value) / 1024l) - 273150;
+			break;
+		default:
+			break;
+		}
+
+		mutex_unlock(&indio_dev->mlock);
+		return IIO_VAL_INT;
+
+	case IIO_CHAN_INFO_SCALE:
+		*val = 3300;
+		*val2 = info->stmpe->mod_12b ? 12 : 10;
+		return IIO_VAL_FRACTIONAL_LOG2;
+
+	default:
+		break;
+	}
+
+	return -EINVAL;
+}
+
+static irqreturn_t stmpe_adc_isr(int irq, void *dev_id)
+{
+	struct stmpe_adc *info = (struct stmpe_adc *)dev_id;
+	u8 data[2];
+
+	if (info->channel > STMPE_TEMP_CHANNEL)
+		return IRQ_NONE;
+
+	if (info->channel <= STMPE_ADC_LAST_NR) {
+		int int_sta;
+
+		int_sta = stmpe_reg_read(info->stmpe, STMPE_REG_ADC_INT_STA);
+
+		/* Is the interrupt relevant */
+		if (!(int_sta & STMPE_ADC_CH(info->channel)))
+			return IRQ_NONE;
+
+		/* Read value */
+		stmpe_block_read(info->stmpe,
+			STMPE_REG_ADC_DATA_CH(info->channel), 2, data);
+
+		stmpe_reg_write(info->stmpe, STMPE_REG_ADC_INT_STA, int_sta);
+	} else if (info->channel == STMPE_TEMP_CHANNEL) {
+		/* Read value */
+		stmpe_block_read(info->stmpe, STMPE_REG_TEMP_DATA, 2, data);
+	}
+
+	info->value = ((u32)data[0] << 8) + data[1];
+	complete(&info->completion);
+
+	return IRQ_HANDLED;
+}
+
+static const struct iio_info stmpe_adc_iio_info = {
+	.read_raw = &stmpe_read_raw,
+};
+
+static void stmpe_adc_voltage_chan(struct iio_chan_spec *ics, int chan)
+{
+	ics->type = IIO_VOLTAGE;
+	ics->info_mask_separate = BIT(IIO_CHAN_INFO_RAW);
+	ics->info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE);
+	ics->indexed = 1;
+	ics->channel = chan;
+}
+
+static void stmpe_adc_temp_chan(struct iio_chan_spec *ics, int chan)
+{
+	ics->type = IIO_TEMP;
+	ics->info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED);
+	ics->indexed = 1;
+	ics->channel = chan;
+}
+
+static int stmpe_adc_init_hw(struct stmpe_adc *adc)
+{
+	struct stmpe *stmpe = adc->stmpe;
+
+	/* use temp irq for each conversion completion */
+	stmpe_reg_write(stmpe, STMPE_REG_TEMP_TH, 0);
+	stmpe_reg_write(stmpe, STMPE_REG_TEMP_TH + 1, 0);
+
+	return 0;
+}
+
+static int stmpe_adc_probe(struct platform_device *pdev)
+{
+	struct iio_dev *indio_dev = NULL;
+	struct stmpe_adc *info = NULL;
+	struct device_node *np;
+	u32 norequest_mask = 0;
+	int irq_temp, irq_adc;
+	int num_chan = 0;
+	int i = 0;
+	int ret;
+
+	irq_adc = platform_get_irq_byname(pdev, "STMPE_ADC");
+	if (irq_adc < 0)
+		return irq_adc;
+
+	indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(struct stmpe_adc));
+	if (!indio_dev) {
+		dev_err(&pdev->dev, "failed allocating iio device\n");
+		return -ENOMEM;
+	}
+
+	info = iio_priv(indio_dev);
+
+	init_completion(&info->completion);
+	ret = devm_request_threaded_irq(&pdev->dev, irq_adc, NULL,
+					stmpe_adc_isr, IRQF_ONESHOT,
+					"stmpe-adc", info);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "failed requesting irq, irq = %d\n",
+				irq_adc);
+		return ret;
+	}
+
+	irq_temp = platform_get_irq_byname(pdev, "STMPE_TEMP_SENS");
+	if (irq_temp >= 0) {
+		ret = devm_request_threaded_irq(&pdev->dev, irq_temp, NULL,
+						stmpe_adc_isr, IRQF_ONESHOT,
+						"stmpe-adc", info);
+		if (ret < 0)
+			dev_warn(&pdev->dev, "failed requesting irq for"
+				 " temp sensor, irq = %d\n", irq_temp);
+	}
+
+	platform_set_drvdata(pdev, indio_dev);
+
+	indio_dev->name		= dev_name(&pdev->dev);
+	indio_dev->dev.parent	= &pdev->dev;
+	indio_dev->info		= &stmpe_adc_iio_info;
+	indio_dev->modes	= INDIO_DIRECT_MODE;
+
+	info->stmpe = dev_get_drvdata(pdev->dev.parent);
+
+	np = pdev->dev.of_node;
+
+	if (!np)
+		dev_err(&pdev->dev, "no device tree node found\n");
+
+	of_property_read_u32(np, "st,norequest-mask", &norequest_mask);
+
+	for_each_clear_bit(i, (unsigned long *) &norequest_mask,
+			   (STMPE_ADC_LAST_NR + 1)) {
+		stmpe_adc_voltage_chan(&info->stmpe_adc_iio_channels[num_chan], i);
+		num_chan++;
+	}
+	stmpe_adc_temp_chan(&info->stmpe_adc_iio_channels[num_chan], i);
+	num_chan++;
+	indio_dev->channels = info->stmpe_adc_iio_channels;
+	indio_dev->num_channels = num_chan;
+
+	ret = stmpe_adc_init_hw(info);
+	if (ret)
+		return ret;
+
+	return iio_device_register(indio_dev);
+}
+
+static int stmpe_adc_remove(struct platform_device *pdev)
+{
+	struct iio_dev *indio_dev = platform_get_drvdata(pdev);
+	struct stmpe_adc *info = iio_priv(indio_dev);
+
+	iio_device_unregister(indio_dev);
+	stmpe_disable(info->stmpe, STMPE_BLOCK_ADC);
+
+	return 0;
+}
+
+static int __maybe_unused stmpe_adc_resume(struct device *dev)
+{
+	struct iio_dev *indio_dev = dev_get_drvdata(dev);
+	struct stmpe_adc *info = iio_priv(indio_dev);
+
+	stmpe_adc_init_hw(info);
+
+	return 0;
+}
+
+static SIMPLE_DEV_PM_OPS(stmpe_adc_pm_ops, NULL, stmpe_adc_resume);
+
+static struct platform_driver stmpe_adc_driver = {
+	.probe		= stmpe_adc_probe,
+	.remove		= stmpe_adc_remove,
+	.driver		= {
+		.name	= "stmpe-adc",
+		.pm	= &stmpe_adc_pm_ops,
+	},
+};
+
+module_platform_driver(stmpe_adc_driver);
+
+MODULE_AUTHOR("Stefan Agner <stefan.agner@xxxxxxxxxxx>");
+MODULE_DESCRIPTION("STMPEXXX ADC driver");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:stmpe-adc");
diff --git a/drivers/input/touchscreen/stmpe-ts.c b/drivers/input/touchscreen/stmpe-ts.c
index c5d9006588a2..81aa313d6e5a 100644
--- a/drivers/input/touchscreen/stmpe-ts.c
+++ b/drivers/input/touchscreen/stmpe-ts.c
@@ -30,8 +30,6 @@
  * with touchscreen controller
  */
 #define STMPE_REG_INT_STA		0x0B
-#define STMPE_REG_ADC_CTRL1		0x20
-#define STMPE_REG_ADC_CTRL2		0x21
 #define STMPE_REG_TSC_CTRL		0x40
 #define STMPE_REG_TSC_CFG		0x41
 #define STMPE_REG_FIFO_TH		0x4A
@@ -58,15 +56,6 @@
  * @idev: registered input device
  * @work: a work item used to scan the device
  * @dev: a pointer back to the MFD cell struct device*
- * @sample_time: ADC converstion time in number of clock.
- * (0 -> 36 clocks, 1 -> 44 clocks, 2 -> 56 clocks, 3 -> 64 clocks,
- * 4 -> 80 clocks, 5 -> 96 clocks, 6 -> 144 clocks),
- * recommended is 4.
- * @mod_12b: ADC Bit mode (0 -> 10bit ADC, 1 -> 12bit ADC)
- * @ref_sel: ADC reference source
- * (0 -> internal reference, 1 -> external reference)
- * @adc_freq: ADC Clock speed
- * (0 -> 1.625 MHz, 1 -> 3.25 MHz, 2 || 3 -> 6.5 MHz)
  * @ave_ctrl: Sample average control
  * (0 -> 1 sample, 1 -> 2 samples, 2 -> 4 samples, 3 -> 8 samples)
  * @touch_det_delay: Touch detect interrupt delay
@@ -88,10 +77,6 @@ struct stmpe_touch {
 	struct input_dev *idev;
 	struct delayed_work work;
 	struct device *dev;
-	u8 sample_time;
-	u8 mod_12b;
-	u8 ref_sel;
-	u8 adc_freq;
 	u8 ave_ctrl;
 	u8 touch_det_delay;
 	u8 settling;
@@ -176,7 +161,7 @@ static irqreturn_t stmpe_ts_handler(int irq, void *data)
 	input_report_key(ts->idev, BTN_TOUCH, 1);
 	input_sync(ts->idev);
 
-       /* flush the FIFO after we have read out our values. */
+	/* flush the FIFO after we have read out our values. */
 	__stmpe_reset_fifo(ts->stmpe);
 
 	/* reenable the tsc */
@@ -202,20 +187,21 @@ static int stmpe_init_hw(struct stmpe_touch *ts)
 		return ret;
 	}
 
-	adc_ctrl1 = STMPE_SAMPLE_TIME(ts->sample_time) |
-		    STMPE_MOD_12B(ts->mod_12b) | STMPE_REF_SEL(ts->ref_sel);
+	adc_ctrl1 = STMPE_SAMPLE_TIME(stmpe->sample_time) |
+		    STMPE_MOD_12B(stmpe->mod_12b) |
+		    STMPE_REF_SEL(stmpe->ref_sel);
 	adc_ctrl1_mask = STMPE_SAMPLE_TIME(0xff) | STMPE_MOD_12B(0xff) |
 			 STMPE_REF_SEL(0xff);
 
-	ret = stmpe_set_bits(stmpe, STMPE_REG_ADC_CTRL1,
+	ret = stmpe_set_bits(stmpe, STMPE811_REG_ADC_CTRL1,
 			adc_ctrl1_mask, adc_ctrl1);
 	if (ret) {
 		dev_err(dev, "Could not setup ADC\n");
 		return ret;
 	}
 
-	ret = stmpe_set_bits(stmpe, STMPE_REG_ADC_CTRL2,
-			STMPE_ADC_FREQ(0xff), STMPE_ADC_FREQ(ts->adc_freq));
+	ret = stmpe_set_bits(stmpe, STMPE811_REG_ADC_CTRL2,
+			STMPE_ADC_FREQ(0xff), STMPE_ADC_FREQ(stmpe->adc_freq));
 	if (ret) {
 		dev_err(dev, "Could not setup ADC\n");
 		return ret;
@@ -295,13 +281,13 @@ static void stmpe_ts_get_platform_info(struct platform_device *pdev,
 
 	if (np) {
 		if (!of_property_read_u32(np, "st,sample-time", &val))
-			ts->sample_time = val;
+			ts->stmpe->sample_time = val;
 		if (!of_property_read_u32(np, "st,mod-12b", &val))
-			ts->mod_12b = val;
+			ts->stmpe->mod_12b = val;
 		if (!of_property_read_u32(np, "st,ref-sel", &val))
-			ts->ref_sel = val;
+			ts->stmpe->ref_sel = val;
 		if (!of_property_read_u32(np, "st,adc-freq", &val))
-			ts->adc_freq = val;
+			ts->stmpe->adc_freq = val;
 		if (!of_property_read_u32(np, "st,ave-ctrl", &val))
 			ts->ave_ctrl = val;
 		if (!of_property_read_u32(np, "st,touch-det-delay", &val))
diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index 8c5dfdce4326..bba159e8eaa4 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -1204,7 +1204,7 @@ config MFD_STMPE
 
 	  Currently supported devices are:
 
-		STMPE811: GPIO, Touchscreen
+		STMPE811: GPIO, Touchscreen, ADC
 		STMPE1601: GPIO, Keypad
 		STMPE1801: GPIO, Keypad
 		STMPE2401: GPIO, Keypad
@@ -1217,6 +1217,7 @@ config MFD_STMPE
 		GPIO: stmpe-gpio
 		Keypad: stmpe-keypad
 		Touchscreen: stmpe-ts
+		ADC: stmpe-adc
 
 menu "STMicroelectronics STMPE Interface Drivers"
 depends on MFD_STMPE
diff --git a/drivers/mfd/stmpe.c b/drivers/mfd/stmpe.c
index 566caca4efd8..35390d1c2e64 100644
--- a/drivers/mfd/stmpe.c
+++ b/drivers/mfd/stmpe.c
@@ -463,6 +463,28 @@ static const struct mfd_cell stmpe_ts_cell = {
 	.num_resources	= ARRAY_SIZE(stmpe_ts_resources),
 };
 
+/*
+ * ADC (STMPE811)
+ */
+
+static struct resource stmpe_adc_resources[] = {
+	{
+		.name	= "STMPE_TEMP_SENS",
+		.flags	= IORESOURCE_IRQ,
+	},
+	{
+		.name	= "STMPE_ADC",
+		.flags	= IORESOURCE_IRQ,
+	},
+};
+
+static const struct mfd_cell stmpe_adc_cell = {
+	.name		= "stmpe-adc",
+	.of_compatible	= "st,stmpe-adc",
+	.resources	= stmpe_adc_resources,
+	.num_resources	= ARRAY_SIZE(stmpe_adc_resources),
+};
+
 /*
  * STMPE811 or STMPE610
  */
@@ -497,6 +519,11 @@ static struct stmpe_variant_block stmpe811_blocks[] = {
 		.irq	= STMPE811_IRQ_TOUCH_DET,
 		.block	= STMPE_BLOCK_TOUCHSCREEN,
 	},
+	{
+		.cell	= &stmpe_adc_cell,
+		.irq	= STMPE811_IRQ_TEMP_SENS,
+		.block	= STMPE_BLOCK_ADC,
+	},
 };
 
 static int stmpe811_enable(struct stmpe *stmpe, unsigned int blocks,
@@ -517,6 +544,44 @@ static int stmpe811_enable(struct stmpe *stmpe, unsigned int blocks,
 				enable ? 0 : mask);
 }
 
+static int stmpe811_init_adc(struct stmpe *stmpe)
+{
+	int ret;
+	u8 adc_ctrl1, adc_ctrl1_mask;
+
+	ret = stmpe_enable(stmpe, STMPE_BLOCK_ADC);
+	if (ret) {
+		dev_err(stmpe->dev, "Could not enable clock for ADC\n");
+		goto err_adc;
+	}
+
+	adc_ctrl1 = STMPE_SAMPLE_TIME(stmpe->sample_time) |
+		    STMPE_MOD_12B(stmpe->mod_12b) |
+		    STMPE_REF_SEL(stmpe->ref_sel);
+	adc_ctrl1_mask = STMPE_SAMPLE_TIME(0xff) | STMPE_MOD_12B(0xff) |
+			 STMPE_REF_SEL(0xff);
+
+	ret = stmpe_set_bits(stmpe, STMPE811_REG_ADC_CTRL1,
+			adc_ctrl1_mask, adc_ctrl1);
+	if (ret) {
+		dev_err(stmpe->dev, "Could not setup ADC\n");
+		goto err_adc;
+	}
+
+	ret = stmpe_set_bits(stmpe, STMPE811_REG_ADC_CTRL2,
+			STMPE_ADC_FREQ(0xff), STMPE_ADC_FREQ(stmpe->adc_freq));
+	if (ret) {
+		dev_err(stmpe->dev, "Could not setup ADC\n");
+		goto err_adc;
+	}
+
+	return 0;
+err_adc:
+	stmpe_disable(stmpe, STMPE_BLOCK_ADC);
+
+	return ret;
+}
+
 static int stmpe811_get_altfunc(struct stmpe *stmpe, enum stmpe_block block)
 {
 	/* 0 for touchscreen, 1 for GPIO */
@@ -1235,6 +1300,12 @@ static int stmpe_chip_init(struct stmpe *stmpe)
 			return ret;
 	}
 
+	if (id == STMPE811_ID) {
+		ret = stmpe811_init_adc(stmpe);
+		if (ret)
+			return ret;
+	}
+
 	return stmpe_reg_write(stmpe, stmpe->regs[STMPE_IDX_ICR_LSB], icr);
 }
 
@@ -1325,6 +1396,7 @@ int stmpe_probe(struct stmpe_client_info *ci, enum stmpe_partnum partnum)
 	struct device_node *np = ci->dev->of_node;
 	struct stmpe *stmpe;
 	int ret;
+	u32 val;
 
 	pdata = devm_kzalloc(ci->dev, sizeof(*pdata), GFP_KERNEL);
 	if (!pdata)
@@ -1342,6 +1414,15 @@ int stmpe_probe(struct stmpe_client_info *ci, enum stmpe_partnum partnum)
 	mutex_init(&stmpe->irq_lock);
 	mutex_init(&stmpe->lock);
 
+	if (!of_property_read_u32(np, "st,sample-time", &val))
+		stmpe->sample_time = val;
+	if (!of_property_read_u32(np, "st,mod-12b", &val))
+		stmpe->mod_12b = val;
+	if (!of_property_read_u32(np, "st,ref-sel", &val))
+		stmpe->ref_sel = val;
+	if (!of_property_read_u32(np, "st,adc-freq", &val))
+		stmpe->adc_freq = val;
+
 	stmpe->dev = ci->dev;
 	stmpe->client = ci->client;
 	stmpe->pdata = pdata;
diff --git a/include/linux/mfd/stmpe.h b/include/linux/mfd/stmpe.h
index c0353f6431f9..86dca9e9880a 100644
--- a/include/linux/mfd/stmpe.h
+++ b/include/linux/mfd/stmpe.h
@@ -21,6 +21,9 @@
 #define STMPE_I_DRIVE(x)	(x & 0x1)
 #define STMPE_OP_MODE(x)	((x & 0x7) << 1)
 
+#define STMPE811_REG_ADC_CTRL1	0x20
+#define STMPE811_REG_ADC_CTRL2	0x21
+
 struct device;
 struct regulator;
 
@@ -134,6 +137,12 @@ struct stmpe {
 	u8 ier[2];
 	u8 oldier[2];
 	struct stmpe_platform_data *pdata;
+
+	/* For devices that use an ADC */
+	u8 sample_time;
+	u8 mod_12b;
+	u8 ref_sel;
+	u8 adc_freq;
 };
 
 extern int stmpe_reg_write(struct stmpe *stmpe, u8 reg, u8 data);
-- 
2.19.1