[PATCH v3 1/7] iio: adc: hi8435: Holt HI-8435 threshold detector

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Add Holt threshold detector driver for HI-8435 chip

Signed-off-by: Vladimir Barinov <vladimir.barinov@xxxxxxxxxxxxxxxxxx>
---
Changes in version 2:
- Added file sysfs-bus-iio-adc-hi8435
- Changed naming from "discrete ADC" to "threshold detector"
- Replaced swab16p/swab32p with be16_to_cpup/be32_to_cpup
- Made *_show and *_store functions static
- moved out from iio buffers to iio events
- removed hi8436/hi8437 chips from the driver
- moved from debounce_soft_delay/enable to debounce_interval via
  IIO_CHAN_INFO_DEBOUNCE_TIME
- added name extention "comparator"
- moved threshold/hysteresis setup via generic iio event sysfs
- added software mask/unmask channel events
- added programming sensor outputs while in test mode via
  IIO_CHAN_INFO_RAW
- added channels .ext_info for programming sensing mode
Changes in version 3:
- fixed typos
- moved <linux/interrupt.h> to match alphabetic order
- fixed missed */event/* prefix in the ABI description
- added missed colon in sysfs-bus-iio-adc-hi8435 file after "What"
- moved in_voltageY_comparator_thresh_either_en and debounce_time
  to sysfs-bus-iio file
- added error checking for hi8435_write[b|w]

 Documentation/ABI/testing/sysfs-bus-iio            |   1 +
 Documentation/ABI/testing/sysfs-bus-iio-adc-hi8435 |  61 ++
 drivers/iio/adc/Kconfig                            |  11 +
 drivers/iio/adc/Makefile                           |   1 +
 drivers/iio/adc/hi8435.c                           | 659 +++++++++++++++++++++
 5 files changed, 742 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-adc-hi8435
 create mode 100644 drivers/iio/adc/hi8435.c

diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
index 70c9b1a..09eac44 100644
--- a/Documentation/ABI/testing/sysfs-bus-iio
+++ b/Documentation/ABI/testing/sysfs-bus-iio
@@ -572,6 +572,7 @@ What:		/sys/.../iio:deviceX/events/in_rot_from_north_magnetic_tilt_comp_thresh_r
 What:		/sys/.../iio:deviceX/events/in_rot_from_north_magnetic_tilt_comp_thresh_falling_en
 What:		/sys/.../iio:deviceX/events/in_rot_from_north_true_tilt_comp_thresh_rising_en
 What:		/sys/.../iio:deviceX/events/in_rot_from_north_true_tilt_comp_thresh_falling_en
+What:		/sys/.../iio:deviceX/events/in_voltageY_comparator_thresh_either_en
 What:		/sys/.../iio:deviceX/events/in_voltageY_supply_thresh_rising_en
 What:		/sys/.../iio:deviceX/events/in_voltageY_supply_thresh_falling_en
 What:		/sys/.../iio:deviceX/events/in_voltageY_thresh_rising_en
diff --git a/Documentation/ABI/testing/sysfs-bus-iio-adc-hi8435 b/Documentation/ABI/testing/sysfs-bus-iio-adc-hi8435
new file mode 100644
index 0000000..c59d81d
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-iio-adc-hi8435
@@ -0,0 +1,61 @@
+What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY_comparator_raw
+Date:		July 2015
+KernelVersion:	4.2.0
+Contact:	source@xxxxxxxxxxxxxxxxxx
+Description:
+		Read value is a voltage threshold measurement from channel Y.
+		Could be either 0 if sensor voltage is lower then low voltage
+		threshold or 1 if sensor voltage is higher then high voltage
+		threshold.
+		Write value is a programmed sensor output while in self test
+		mode. Could be either 0 or 1. The programmed value will be read
+		back if /sys/bus/iio/devices/iio:deviceX/test_enable is set to 1.
+
+What:		/sys/bus/iio/devices/iio:deviceX/test_enable
+Date:		July 2015
+KernelVersion:	4.2.0
+Contact:	source@xxxxxxxxxxxxxxxxxx
+Description:
+		Enable/disable the HI-8435 self test mode.
+		If enabled the in_voltageY_comparator_raw should be read back
+		accordingly to written value to in_voltageY_comparator_raw.
+
+What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY_comparator_sensing_mode
+Date:		July 2015
+KernelVersion:	4.2.0
+Contact:	source@xxxxxxxxxxxxxxxxxx
+Description:
+		Program sensor type for threshold detector inputs.
+		Could be either "GND-Open" or "Supply-Open" mode. Y is a
+		threshold detector input channel. Channels 0..7, 8..15, 16..23
+		and 24..31 has common sensor types.
+
+What:		/sys/bus/iio/devices/iio:deviceX/events/in_voltageY_comparator_thresh_falling_value
+Date:		July 2015
+KernelVersion:	4.2.0
+Contact:	source@xxxxxxxxxxxxxxxxxx
+Description:
+		Channel Y low voltage threshold. If sensor input voltage goes lower then
+		this value then the threshold falling event is pushed.
+		Depending on in_voltageY_comparator_sensing_mode the low voltage threshold
+		is separately set for "GND-Open" and "Supply-Open" modes.
+		Channels 0..31 have common low threshold values, but could have different
+		sensing_modes.
+		The low voltage threshold range is between 2..21V.
+		Hysteresis between low and high thresholds can not be lower then 2 and
+		can not be odd.
+
+What:		/sys/bus/iio/devices/iio:deviceX/events/in_voltageY_comparator_thresh_rising_value
+Date:		July 2015
+KernelVersion:	4.2.0
+Contact:	source@xxxxxxxxxxxxxxxxxx
+Description:
+		Channel Y high voltage threshold. If sensor input voltage goes higher then
+		this value then the threshold rising event is pushed.
+		Depending on in_voltageY_comparator_sensing_mode the high voltage threshold
+		is separately set for "GND-Open" and "Supply-Open" modes.
+		Channels 0..31 have common high threshold values, but could have different
+		sensing_modes.
+		The high voltage threshold range is between 3..22V.
+		Hysteresis between low and high thresholds can not be lower then 2 and
+		can not be odd.
diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index eb0cd89..553c91e 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -170,6 +170,17 @@ config EXYNOS_ADC
 	  of SoCs for drivers such as the touchscreen and hwmon to use to share
 	  this resource.
 
+config HI8435
+	tristate "Holt Integrated Circuits HI-8435 threshold detector"
+	select IIO_TRIGGERED_EVENT
+	depends on SPI
+	help
+	  If you say yes here you get support for Holt Integrated Circuits
+	  HI-8435 chip.
+
+	  This driver can also be built as a module. If so, the module will be
+	  called hi8435.
+
 config LP8788_ADC
 	tristate "LP8788 ADC driver"
 	depends on MFD_LP8788
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index a096210..00f367aa 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -19,6 +19,7 @@ obj-$(CONFIG_BERLIN2_ADC) += berlin2-adc.o
 obj-$(CONFIG_DA9150_GPADC) += da9150-gpadc.o
 obj-$(CONFIG_CC10001_ADC) += cc10001_adc.o
 obj-$(CONFIG_EXYNOS_ADC) += exynos_adc.o
+obj-$(CONFIG_HI8435) += hi8435.o
 obj-$(CONFIG_LP8788_ADC) += lp8788_adc.o
 obj-$(CONFIG_MAX1027) += max1027.o
 obj-$(CONFIG_MAX1363) += max1363.o
diff --git a/drivers/iio/adc/hi8435.c b/drivers/iio/adc/hi8435.c
new file mode 100644
index 0000000..f3dab5a
--- /dev/null
+++ b/drivers/iio/adc/hi8435.c
@@ -0,0 +1,659 @@
+/*
+ * Holt Integrated Circuits HI-8435 threshold detector driver
+ *
+ * Copyright (C) 2015 Zodiac Inflight Innovations
+ * Copyright (C) 2015 Cogent Embedded, Inc.
+ *
+ * This program is free software; you can redistribute  it and/or modify it
+ * under  the terms of  the GNU General  Public License as published by the
+ * Free Software Foundation;  either version 2 of the  License, or (at your
+ * option) any later version.
+ */
+
+#include <linux/delay.h>
+#include <linux/iio/events.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+#include <linux/iio/trigger.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/iio/triggered_event.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/of_gpio.h>
+#include <linux/spi/spi.h>
+#include <linux/workqueue.h>
+
+#define DRV_NAME "hi8435"
+
+/* Register offsets for HI-8435 */
+#define HI8435_CTRL_REG			0x02
+#define HI8435_PSEN_REG			0x04
+#define HI8435_TMDATA_REG		0x1E
+#define HI8435_GOCENHYS_REG		0x3A
+#define HI8435_SOCENHYS_REG		0x3C
+#define HI8435_SO7_0_REG		0x10
+#define HI8435_SO15_8_REG		0x12
+#define HI8435_SO23_16_REG		0x14
+#define HI8435_SO31_24_REG		0x16
+#define HI8435_SO31_0_REG		0x78
+
+#define HI8435_WRITE_OPCODE		0x00
+#define HI8435_READ_OPCODE		0x80
+
+/* CTRL register bits */
+#define HI8435_CTRL_TEST		0x01
+#define HI8435_CTRL_SRST		0x02
+
+#define HI8435_DEBOUNCE_DELAY_MAX	1000	/* msec */
+#define HI8435_DEBOUNCE_DELAY_DEF	100	/* msec */
+
+struct hi8435_priv {
+	struct spi_device *spi;
+	struct mutex lock;
+	struct delayed_work work;
+
+	int reset_gpio;
+	int debounce_interval; /* msec */
+	u32 debounce_val; /* prev value to compare during software debounce */
+
+	unsigned long event_scan_mask; /* soft mask/unmask channels events */
+	unsigned int event_prev_val;
+
+	unsigned threshold_lo[2]; /* GND-Open and Supply-Open thresholds */
+	unsigned threshold_hi[2]; /* GND-Open and Supply-Open threshold */
+	u8 reg_buffer[4] ____cacheline_aligned;
+};
+
+static int hi8435_readb(struct hi8435_priv *priv, u8 reg, u8 *val)
+{
+	reg |= HI8435_READ_OPCODE;
+	return spi_write_then_read(priv->spi, &reg, 1, val, 1);
+}
+
+static int hi8435_readw(struct hi8435_priv *priv, u8 reg, u16 *val)
+{
+	int ret;
+
+	reg |= HI8435_READ_OPCODE;
+	ret = spi_write_then_read(priv->spi, &reg, 1, val, 2);
+	*val = be16_to_cpup(val);
+
+	return ret;
+}
+
+static int hi8435_readl(struct hi8435_priv *priv, u8 reg, u32 *val)
+{
+	int ret;
+
+	reg |= HI8435_READ_OPCODE;
+	ret = spi_write_then_read(priv->spi, &reg, 1, val, 4);
+	*val = be32_to_cpup(val);
+
+	return ret;
+}
+
+static int hi8435_writeb(struct hi8435_priv *priv, u8 reg, u8 val)
+{
+	priv->reg_buffer[0] = reg | HI8435_WRITE_OPCODE;
+	priv->reg_buffer[1] = val;
+
+	return spi_write(priv->spi, priv->reg_buffer, 2);
+}
+
+static int hi8435_writew(struct hi8435_priv *priv, u8 reg, u16 val)
+{
+	priv->reg_buffer[0] = reg | HI8435_WRITE_OPCODE;
+	priv->reg_buffer[1] = (val >> 8) & 0xff;
+	priv->reg_buffer[2] = val & 0xff;
+
+	return spi_write(priv->spi, priv->reg_buffer, 3);
+}
+
+static ssize_t hi8435_test_enable_show(struct device *dev,
+				       struct device_attribute *attr, char *buf)
+{
+	struct hi8435_priv *priv = iio_priv(dev_to_iio_dev(dev));
+	int ret;
+	u8 reg;
+
+	ret = hi8435_readb(priv, HI8435_CTRL_REG, &reg);
+	if (ret < 0)
+		return ret;
+
+	return sprintf(buf, "%d\n", reg & HI8435_CTRL_TEST);
+}
+
+static ssize_t hi8435_test_enable_store(struct device *dev,
+					struct device_attribute *attr,
+					const char *buf, size_t len)
+{
+	struct hi8435_priv *priv = iio_priv(dev_to_iio_dev(dev));
+	unsigned int val;
+	int ret;
+
+	ret = kstrtouint(buf, 10, &val);
+	if (ret)
+		return ret;
+
+	ret = hi8435_writeb(priv, HI8435_CTRL_REG, val ? HI8435_CTRL_TEST : 0);
+	if (ret < 0)
+		return ret;
+
+	return len;
+}
+
+static IIO_DEVICE_ATTR(test_enable, S_IRUGO | S_IWUSR,
+	hi8435_test_enable_show, hi8435_test_enable_store, 0);
+
+static struct attribute *hi8435_attributes[] = {
+	&iio_dev_attr_test_enable.dev_attr.attr,
+	NULL,
+};
+
+static struct attribute_group hi8435_attribute_group = {
+	.attrs = hi8435_attributes,
+};
+
+static int hi8435_read_raw(struct iio_dev *idev,
+			   const struct iio_chan_spec *chan,
+			   int *val, int *val2, long mask)
+{
+	struct hi8435_priv *priv = iio_priv(idev);
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		ret = hi8435_readl(priv, HI8435_SO31_0_REG, val);
+		if (ret < 0)
+			return ret;
+		*val = !!(*val & BIT(chan->channel));
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_DEBOUNCE_TIME:
+		*val = priv->debounce_interval;
+		return IIO_VAL_INT;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int hi8435_write_raw(struct iio_dev *idev,
+			    const struct iio_chan_spec *chan,
+			    int val, int val2, long mask)
+{
+	struct hi8435_priv *priv = iio_priv(idev);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		/* program sensors outputs in test mode */
+		return hi8435_writeb(priv, HI8435_TMDATA_REG, val ? 0x1 : 0x2);
+	case IIO_CHAN_INFO_DEBOUNCE_TIME:
+		if (val < 0)
+			return -EINVAL;
+		if (val > HI8435_DEBOUNCE_DELAY_MAX)
+			val = HI8435_DEBOUNCE_DELAY_MAX;
+		priv->debounce_interval = val;
+		return 0;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int hi8435_read_event_config(struct iio_dev *idev,
+				    const struct iio_chan_spec *chan,
+				    enum iio_event_type type,
+				    enum iio_event_direction dir)
+{
+	struct hi8435_priv *priv = iio_priv(idev);
+
+	return !!(priv->event_scan_mask & BIT(chan->channel));
+}
+
+static int hi8435_write_event_config(struct iio_dev *idev,
+				     const struct iio_chan_spec *chan,
+				     enum iio_event_type type,
+				     enum iio_event_direction dir, int state)
+{
+	struct hi8435_priv *priv = iio_priv(idev);
+
+	priv->event_scan_mask &= ~BIT(chan->channel);
+	if (state)
+		priv->event_scan_mask |= BIT(chan->channel);
+
+	return 0;
+}
+
+static int hi8435_read_event_value(struct iio_dev *idev,
+				   const struct iio_chan_spec *chan,
+				   enum iio_event_type type,
+				   enum iio_event_direction dir,
+				   enum iio_event_info info,
+				   int *val, int *val2)
+{
+	struct hi8435_priv *priv = iio_priv(idev);
+	int ret;
+	u8 mode, psen;
+	u16 reg;
+
+	ret = hi8435_readb(priv, HI8435_PSEN_REG, &psen);
+	if (ret < 0)
+		return ret;
+
+	/* Supply-Open or GND-Open sensing mode */
+	mode = !!(psen & BIT(chan->channel / 8));
+
+	ret = hi8435_readw(priv, mode ? HI8435_SOCENHYS_REG :
+				 HI8435_GOCENHYS_REG, &reg);
+	if (ret < 0)
+		return ret;
+
+	if (dir == IIO_EV_DIR_FALLING)
+		*val = ((reg & 0xff) - (reg >> 8)) / 2;
+
+	if (dir == IIO_EV_DIR_RISING)
+		*val = ((reg & 0xff) + (reg >> 8)) / 2;
+
+	return IIO_VAL_INT;
+}
+
+static int hi8435_write_event_value(struct iio_dev *idev,
+				    const struct iio_chan_spec *chan,
+				    enum iio_event_type type,
+				    enum iio_event_direction dir,
+				    enum iio_event_info info,
+				    int val, int val2)
+{
+	struct hi8435_priv *priv = iio_priv(idev);
+	int ret;
+	u8 mode, psen;
+	u16 reg;
+
+	ret = hi8435_readb(priv, HI8435_PSEN_REG, &psen);
+	if (ret < 0)
+		return ret;
+
+	/* Supply-Open or GND-Open sensing mode */
+	mode = !!(psen & BIT(chan->channel / 8));
+
+	ret = hi8435_readw(priv, mode ? HI8435_SOCENHYS_REG :
+				 HI8435_GOCENHYS_REG, &reg);
+	if (ret < 0)
+		return ret;
+
+	if (dir == IIO_EV_DIR_FALLING) {
+		/* falling threshold range 2..21V, hysteresis minimum 2V */
+		if (val < 2 || val > 21 || (val + 1) >= priv->threshold_hi[mode])
+			return -EINVAL;
+
+		if (val == priv->threshold_lo[mode])
+			return 0;
+
+		priv->threshold_lo[mode] = val;
+
+		/* hysteresis must not be odd */
+		if ((priv->threshold_hi[mode] - priv->threshold_lo[mode]) % 2)
+			priv->threshold_hi[mode]--;
+	}
+
+	if (dir == IIO_EV_DIR_RISING) {
+		/* rising threshold range 3..22V, hysteresis minimum 2V */
+		if (val < 3 || val > 22 || val <= (priv->threshold_lo[mode] + 1))
+			return -EINVAL;
+
+		if (val == priv->threshold_hi[mode])
+			return 0;
+
+		priv->threshold_hi[mode] = val;
+
+		/* hysteresis must not be odd */
+		if ((priv->threshold_hi[mode] - priv->threshold_lo[mode]) % 2)
+			priv->threshold_lo[mode]++;
+	}
+
+	/* program thresholds */
+	mutex_lock(&priv->lock);
+
+	ret = hi8435_readw(priv, mode ? HI8435_SOCENHYS_REG :
+				 HI8435_GOCENHYS_REG, &reg);
+	if (ret < 0) {
+		mutex_unlock(&priv->lock);
+		return ret;
+	}
+
+	/* hysteresis */
+	reg = priv->threshold_hi[mode] - priv->threshold_lo[mode];
+	reg <<= 8;
+	/* threshold center */
+	reg |= (priv->threshold_hi[mode] + priv->threshold_lo[mode]);
+
+	ret = hi8435_writew(priv, mode ? HI8435_SOCENHYS_REG :
+				  HI8435_GOCENHYS_REG, reg);
+
+	mutex_unlock(&priv->lock);
+
+	return ret;
+}
+
+static const struct iio_event_spec hi8435_events[] = {
+	{
+		.type = IIO_EV_TYPE_THRESH,
+		.dir = IIO_EV_DIR_RISING,
+		.mask_separate = BIT(IIO_EV_INFO_VALUE),
+	}, {
+		.type = IIO_EV_TYPE_THRESH,
+		.dir = IIO_EV_DIR_FALLING,
+		.mask_separate = BIT(IIO_EV_INFO_VALUE),
+	}, {
+		.type = IIO_EV_TYPE_THRESH,
+		.dir = IIO_EV_DIR_EITHER,
+		.mask_separate = BIT(IIO_EV_INFO_ENABLE),
+	},
+};
+
+static int hi8435_get_sensing_mode(struct iio_dev *idev,
+				   const struct iio_chan_spec *chan)
+{
+	struct hi8435_priv *priv = iio_priv(idev);
+	int ret;
+	u8 reg;
+
+	ret = hi8435_readb(priv, HI8435_PSEN_REG, &reg);
+	if (ret < 0)
+		return ret;
+
+	return !!(reg & BIT(chan->channel / 8));
+}
+
+static int hi8435_set_sensing_mode(struct iio_dev *idev,
+				   const struct iio_chan_spec *chan,
+				   unsigned int mode)
+{
+	struct hi8435_priv *priv = iio_priv(idev);
+	int ret;
+	u8 reg;
+
+	mutex_lock(&priv->lock);
+
+	ret = hi8435_readb(priv, HI8435_PSEN_REG, &reg);
+	if (ret < 0) {
+		mutex_unlock(&priv->lock);
+		return ret;
+	}
+
+	reg &= ~BIT(chan->channel / 8);
+	if (mode)
+		reg |= BIT(chan->channel / 8);
+
+	ret = hi8435_writeb(priv, HI8435_PSEN_REG, reg);
+
+	mutex_unlock(&priv->lock);
+
+	return ret;
+}
+
+static const char * const hi8435_sensing_modes[] = { "GND-Open",
+						     "Supply-Open" };
+
+static const struct iio_enum hi8435_sensing_mode = {
+	.items = hi8435_sensing_modes,
+	.num_items = ARRAY_SIZE(hi8435_sensing_modes),
+	.get = hi8435_get_sensing_mode,
+	.set = hi8435_set_sensing_mode,
+};
+
+static const struct iio_chan_spec_ext_info hi8435_ext_info[] = {
+	IIO_ENUM("sensing_mode", IIO_SEPARATE, &hi8435_sensing_mode),
+	{},
+};
+
+#define HI8435_VOLTAGE_CHANNEL(num)					\
+{									\
+	.type = IIO_VOLTAGE,						\
+	.indexed = 1,							\
+	.channel = num,							\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),			\
+	.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_DEBOUNCE_TIME),	\
+	.event_spec = hi8435_events,					\
+	.num_event_specs = ARRAY_SIZE(hi8435_events),			\
+	.ext_info = hi8435_ext_info,					\
+	.extend_name = "comparator"					\
+}
+
+static const struct iio_chan_spec hi8435_channels[] = {
+	HI8435_VOLTAGE_CHANNEL(0),
+	HI8435_VOLTAGE_CHANNEL(1),
+	HI8435_VOLTAGE_CHANNEL(2),
+	HI8435_VOLTAGE_CHANNEL(3),
+	HI8435_VOLTAGE_CHANNEL(4),
+	HI8435_VOLTAGE_CHANNEL(5),
+	HI8435_VOLTAGE_CHANNEL(6),
+	HI8435_VOLTAGE_CHANNEL(7),
+	HI8435_VOLTAGE_CHANNEL(8),
+	HI8435_VOLTAGE_CHANNEL(9),
+	HI8435_VOLTAGE_CHANNEL(10),
+	HI8435_VOLTAGE_CHANNEL(11),
+	HI8435_VOLTAGE_CHANNEL(12),
+	HI8435_VOLTAGE_CHANNEL(13),
+	HI8435_VOLTAGE_CHANNEL(14),
+	HI8435_VOLTAGE_CHANNEL(15),
+	HI8435_VOLTAGE_CHANNEL(16),
+	HI8435_VOLTAGE_CHANNEL(17),
+	HI8435_VOLTAGE_CHANNEL(18),
+	HI8435_VOLTAGE_CHANNEL(19),
+	HI8435_VOLTAGE_CHANNEL(20),
+	HI8435_VOLTAGE_CHANNEL(21),
+	HI8435_VOLTAGE_CHANNEL(22),
+	HI8435_VOLTAGE_CHANNEL(23),
+	HI8435_VOLTAGE_CHANNEL(24),
+	HI8435_VOLTAGE_CHANNEL(25),
+	HI8435_VOLTAGE_CHANNEL(26),
+	HI8435_VOLTAGE_CHANNEL(27),
+	HI8435_VOLTAGE_CHANNEL(28),
+	HI8435_VOLTAGE_CHANNEL(29),
+	HI8435_VOLTAGE_CHANNEL(30),
+	HI8435_VOLTAGE_CHANNEL(31),
+	IIO_CHAN_SOFT_TIMESTAMP(32),
+};
+
+static const struct iio_info hi8435_info = {
+	.driver_module = THIS_MODULE,
+	.attrs = &hi8435_attribute_group,
+	.read_raw = hi8435_read_raw,
+	.write_raw = hi8435_write_raw,
+	.read_event_config = &hi8435_read_event_config,
+	.write_event_config = hi8435_write_event_config,
+	.read_event_value = &hi8435_read_event_value,
+	.write_event_value = &hi8435_write_event_value,
+};
+
+static void hi8435_iio_push_event(struct iio_dev *idev, unsigned int val)
+{
+	struct hi8435_priv *priv = iio_priv(idev);
+	enum iio_event_direction dir;
+	unsigned int i;
+	unsigned int status = priv->event_prev_val ^ val;
+
+	if (!status)
+		return;
+
+	for_each_set_bit(i, &priv->event_scan_mask, 32) {
+		if (!(status & BIT(i)))
+			continue;
+
+		dir = val & BIT(i) ? IIO_EV_DIR_RISING : IIO_EV_DIR_FALLING;
+
+		iio_push_event(idev,
+			       IIO_UNMOD_EVENT_CODE(IIO_VOLTAGE, i,
+						    IIO_EV_TYPE_THRESH, dir),
+			       iio_get_time_ns());
+	}
+
+	priv->event_prev_val = val;
+}
+
+static void hi8435_debounce_work(struct work_struct *work)
+{
+	struct hi8435_priv *priv = container_of(work, struct hi8435_priv,
+						work.work);
+	struct iio_dev *idev = spi_get_drvdata(priv->spi);
+	u32 val;
+	int ret;
+
+	ret = hi8435_readl(priv, HI8435_SO31_0_REG, &val);
+	if (ret < 0)
+		return;
+
+	if (val == priv->debounce_val)
+		hi8435_iio_push_event(idev, val);
+	else
+		dev_warn(&priv->spi->dev, "filtered by software debounce");
+}
+
+static irqreturn_t hi8435_trigger_handler(int irq, void *private)
+{
+	struct iio_poll_func *pf = private;
+	struct iio_dev *idev = pf->indio_dev;
+	struct hi8435_priv *priv = iio_priv(idev);
+	u32 val;
+	int ret;
+
+	ret = hi8435_readl(priv, HI8435_SO31_0_REG, &val);
+	if (ret < 0)
+		goto err_read;
+
+	if (priv->debounce_interval) {
+		priv->debounce_val = val;
+		schedule_delayed_work(&priv->work,
+				msecs_to_jiffies(priv->debounce_interval));
+	} else {
+		hi8435_iio_push_event(idev, val);
+	}
+
+err_read:
+	iio_trigger_notify_done(idev->trig);
+
+	return IRQ_HANDLED;
+}
+
+static void hi8435_parse_dt(struct hi8435_priv *priv)
+{
+	struct device_node *np = priv->spi->dev.of_node;
+	int ret;
+
+	ret = of_get_named_gpio(np, "holt,reset-gpios", 0);
+	priv->reset_gpio = ret < 0 ? 0 : ret;
+
+	ret = of_property_read_u32(np, "holt,debounce-interval",
+				   &priv->debounce_interval);
+	if (ret)
+		priv->debounce_interval = 0;
+	if (priv->debounce_interval > HI8435_DEBOUNCE_DELAY_MAX)
+		priv->debounce_interval = HI8435_DEBOUNCE_DELAY_MAX;
+}
+
+static int hi8435_probe(struct spi_device *spi)
+{
+	struct iio_dev *idev;
+	struct hi8435_priv *priv;
+	int ret;
+
+	idev = devm_iio_device_alloc(&spi->dev, sizeof(*priv));
+	if (!idev)
+		return -ENOMEM;
+
+	priv = iio_priv(idev);
+	priv->spi = spi;
+
+	if (spi->dev.of_node)
+		hi8435_parse_dt(priv);
+
+	spi_set_drvdata(spi, idev);
+	mutex_init(&priv->lock);
+	INIT_DELAYED_WORK(&priv->work, hi8435_debounce_work);
+
+	idev->dev.parent	= &spi->dev;
+	idev->name		= spi_get_device_id(spi)->name;
+	idev->modes		= INDIO_DIRECT_MODE;
+	idev->info		= &hi8435_info;
+	idev->channels		= hi8435_channels;
+	idev->num_channels	= ARRAY_SIZE(hi8435_channels);
+
+	if (priv->reset_gpio) {
+		ret = devm_gpio_request(&spi->dev, priv->reset_gpio, idev->name);
+		if (!ret) {
+			/* chip hardware reset */
+			gpio_direction_output(priv->reset_gpio, 0);
+			udelay(5);
+			gpio_direction_output(priv->reset_gpio, 1);
+		}
+	} else {
+		/* chip software reset */
+		hi8435_writeb(priv, HI8435_CTRL_REG, HI8435_CTRL_SRST);
+		/* get out from reset state */
+		hi8435_writeb(priv, HI8435_CTRL_REG, 0);
+	}
+
+	/* unmask all events */
+	priv->event_scan_mask = ~(0);
+	/* initialize default thresholds */
+	priv->threshold_lo[0] = priv->threshold_lo[1] = 2;
+	priv->threshold_hi[0] = priv->threshold_hi[1] = 4;
+	hi8435_writew(priv, HI8435_GOCENHYS_REG, 0x206);
+	hi8435_writew(priv, HI8435_SOCENHYS_REG, 0x206);
+
+	ret = iio_triggered_event_setup(idev, NULL, hi8435_trigger_handler);
+	if (ret)
+		return ret;
+
+	ret = iio_device_register(idev);
+	if (ret < 0) {
+		dev_err(&spi->dev, "unable to register device\n");
+		goto unregister_triggered_event;
+	}
+
+	return 0;
+
+unregister_triggered_event:
+	iio_triggered_event_cleanup(idev);
+	return ret;
+}
+
+static int hi8435_remove(struct spi_device *spi)
+{
+	struct iio_dev *idev = spi_get_drvdata(spi);
+	struct hi8435_priv *priv = iio_priv(idev);
+
+	cancel_delayed_work_sync(&priv->work);
+	iio_device_unregister(idev);
+	iio_triggered_event_cleanup(idev);
+
+	return 0;
+}
+
+static const struct of_device_id hi8435_dt_ids[] = {
+	{ .compatible = "holt,hi8435" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, hi8435_dt_ids);
+
+static const struct spi_device_id hi8435_id[] = {
+	{ "hi8435", 0},
+	{ }
+};
+MODULE_DEVICE_TABLE(spi, hi8435_id);
+
+static struct spi_driver hi8435_driver = {
+	.driver	= {
+		.name		= DRV_NAME,
+		.of_match_table	= of_match_ptr(hi8435_dt_ids),
+	},
+	.probe		= hi8435_probe,
+	.remove		= hi8435_remove,
+	.id_table	= hi8435_id,
+};
+module_spi_driver(hi8435_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Vladimir Barinov");
+MODULE_DESCRIPTION("HI-8435 threshold detector");
-- 
1.9.1

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