iio: light: add driver for Capella CM3605

This adds a driver for the Capella Microsystems CM3605 Ambient
Light Sensor and proximity sensor. This is a pretty simple entirely
analog device that is interfaced with the target system using
the POUT (proximity out) and AOUT (ambient light out) signals.

The POUT signal is a simple high/low signal that indicates whether
an object is in proximity, most typically used to detect a face
in front of a mobile device. The signal requires that an infrared
LED is mounted next to the device, making IR light reflect off
the object in proximity and triggering the POUT signal. We grab
a GPIO pin to handle the POUT signal as an interrupt line and
register this as an event channel for the sensor.

Since the proximity sensor requires an IR LED, we add a LED trigger
named "cm3605" so that the infrared LED can just associate with
this trigger to be sure it is always on when the proximity sensor
needs it.

The AOUT is an analog voltage between 0 and 1550 mV that indicate
the LUX value in the ambient light: this is orthogonal to the
proximity sensor functionality. Since this analog voltage needs
to be converted into a digital value, the driver grabs an IIO
channel named "aout" associated with the device.

This patch created a combined ALS and proximity sensor driver.
The former supports raw reads of the LUX value and the latter
will generate proximity events.

To integrate this properly with Linux we also add a supply
regulator for the VDD pin (driving both functions) and add device
tree bindings to define the RSET resistor that in turn configures
the luminosity range of the ALS sensor.

Since the sensor needs to be on more or less constantly, we
restrict the power management to system suspend/resume: we
disable the IR LED and disable the regulator for VDD on suspend
and take them back up on resume.

Tests:
cd /sys/bus/iio/devices/iio:device1
cat in_illuminance_raw
304
(hold hand over sensor)
cat in_illuminance_raw
17
iio_event_monitor cm3605
Found IIO device with name cm3605 with device number 1
(hold hand over sensor)
Event: time: 2444842301447, type: proximity, channel: 0,
  evtype: thresh, direction: falling
(remove hand over sensor)
Event: time: 2445583440706, type: proximity, channel: 0,
  evtype: thresh, direction: rising

Cc: Capella Microsystems <capellamicro@gmail.com>
Cc: Kevin Tsai <ktsai@capellamicro.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/light/Kconfig

@@ -115,6 +115,16 @@ config CM3323
 	 To compile this driver as a module, choose M here: the module will
 	 be called cm3323.
 
+config CM3605
+	tristate "Capella CM3605 ambient light and proximity sensor"
+	depends on OF
+	help
+	 Say Y here if you want to build a driver for Capella CM3605
+	 ambient light and short range proximity sensor.
+
+	 To compile this driver as a module, choose M here: the module will
+	 be called cm3605.
+
 config CM36651
 	depends on I2C
 	tristate "CM36651 driver"

drivers/iio/light/Makefile

@@ -13,6 +13,7 @@ obj-$(CONFIG_BH1780)		+= bh1780.o
 obj-$(CONFIG_CM32181)		+= cm32181.o
 obj-$(CONFIG_CM3232)		+= cm3232.o
 obj-$(CONFIG_CM3323)		+= cm3323.o
+obj-$(CONFIG_CM3605)		+= cm3605.o
 obj-$(CONFIG_CM36651)		+= cm36651.o
 obj-$(CONFIG_GP2AP020A00F)	+= gp2ap020a00f.o
 obj-$(CONFIG_HID_SENSOR_ALS)	+= hid-sensor-als.o

drivers/iio/light/cm3605.c

@@ -0,0 +1,330 @@
+/*
+ * CM3605 Ambient Light and Proximity Sensor
+ *
+ * Copyright (C) 2016 Linaro Ltd.
+ * Author: Linus Walleij <linus.walleij@linaro.org>
+ *
+ * This hardware was found in the very first Nexus One handset from Google/HTC
+ * and an early endavour into mobile light and proximity sensors.
+ */
+
+#include <linux/module.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+#include <linux/iio/events.h>
+#include <linux/iio/consumer.h> /* To get our ADC channel */
+#include <linux/iio/types.h> /* To deal with our ADC channel */
+#include <linux/init.h>
+#include <linux/leds.h>
+#include <linux/platform_device.h>
+#include <linux/of.h>
+#include <linux/regulator/consumer.h>
+#include <linux/gpio/consumer.h>
+#include <linux/interrupt.h>
+#include <linux/math64.h>
+#include <linux/pm.h>
+
+#define CM3605_PROX_CHANNEL 0
+#define CM3605_ALS_CHANNEL 1
+#define CM3605_AOUT_TYP_MAX_MV 1550
+/* It should not go above 1.650V according to the data sheet */
+#define CM3605_AOUT_MAX_MV 1650
+
+/**
+ * struct cm3605 - CM3605 state
+ * @dev: pointer to parent device
+ * @vdd: regulator controlling VDD
+ * @aset: sleep enable GPIO, high = sleep
+ * @aout: IIO ADC channel to convert the AOUT signal
+ * @als_max: maximum LUX detection (depends on RSET)
+ * @dir: proximity direction: start as FALLING
+ * @led: trigger for the infrared LED used by the proximity sensor
+ */
+struct cm3605 {
+	struct device *dev;
+	struct regulator *vdd;
+	struct gpio_desc *aset;
+	struct iio_channel *aout;
+	s32 als_max;
+	enum iio_event_direction dir;
+	struct led_trigger *led;
+};
+
+static irqreturn_t cm3605_prox_irq(int irq, void *d)
+{
+	struct iio_dev *indio_dev = d;
+	struct cm3605 *cm3605 = iio_priv(indio_dev);
+	u64 ev;
+
+	ev = IIO_UNMOD_EVENT_CODE(IIO_PROXIMITY, CM3605_PROX_CHANNEL,
+				  IIO_EV_TYPE_THRESH, cm3605->dir);
+	iio_push_event(indio_dev, ev, iio_get_time_ns(indio_dev));
+
+	/* Invert the edge for each event */
+	if (cm3605->dir == IIO_EV_DIR_RISING)
+		cm3605->dir = IIO_EV_DIR_FALLING;
+	else
+		cm3605->dir = IIO_EV_DIR_RISING;
+
+	return IRQ_HANDLED;
+}
+
+static int cm3605_get_lux(struct cm3605 *cm3605)
+{
+	int ret, res;
+	s64 lux;
+
+	ret = iio_read_channel_processed(cm3605->aout, &res);
+	if (ret < 0)
+		return ret;
+
+	dev_dbg(cm3605->dev, "read %d mV from ADC\n", res);
+
+	/*
+	 * AOUT has an offset of ~30mV then linear at dark
+	 * then goes from 2.54 up to 650 LUX yielding 1.55V
+	 * (1550 mV) so scale the returned value to this interval
+	 * using simple linear interpolation.
+	 */
+	if (res < 30)
+		return 0;
+	if (res > CM3605_AOUT_MAX_MV)
+		dev_err(cm3605->dev, "device out of range\n");
+
+	/* Remove bias */
+	lux = res - 30;
+
+	/* Linear interpolation between 0 and ALS typ max */
+	lux *= cm3605->als_max;
+	lux = div64_s64(lux, CM3605_AOUT_TYP_MAX_MV);
+
+	return lux;
+}
+
+static int cm3605_read_raw(struct iio_dev *indio_dev,
+			   struct iio_chan_spec const *chan,
+			   int *val, int *val2, long mask)
+{
+	struct cm3605 *cm3605 = iio_priv(indio_dev);
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		switch (chan->type) {
+		case IIO_LIGHT:
+			ret = cm3605_get_lux(cm3605);
+			if (ret < 0)
+				return ret;
+			*val = ret;
+			return IIO_VAL_INT;
+		default:
+			return -EINVAL;
+		}
+	default:
+		return -EINVAL;
+	}
+}
+
+static const struct iio_info cm3605_info = {
+	.driver_module = THIS_MODULE,
+	.read_raw = cm3605_read_raw,
+};
+
+static const struct iio_event_spec cm3605_events[] = {
+	{
+		.type = IIO_EV_TYPE_THRESH,
+		.dir = IIO_EV_DIR_EITHER,
+		.mask_separate = BIT(IIO_EV_INFO_ENABLE),
+	},
+};
+
+static const struct iio_chan_spec cm3605_channels[] = {
+	{
+		.type = IIO_PROXIMITY,
+		.event_spec = cm3605_events,
+		.num_event_specs = ARRAY_SIZE(cm3605_events),
+	},
+	{
+		.type = IIO_LIGHT,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
+		.channel = CM3605_ALS_CHANNEL,
+	},
+};
+
+static int cm3605_probe(struct platform_device *pdev)
+{
+	struct cm3605 *cm3605;
+	struct iio_dev *indio_dev;
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node;
+	enum iio_chan_type ch_type;
+	u32 rset;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*cm3605));
+	if (!indio_dev)
+		return -ENOMEM;
+	platform_set_drvdata(pdev, indio_dev);
+
+	cm3605 = iio_priv(indio_dev);
+	cm3605->dev = dev;
+	cm3605->dir = IIO_EV_DIR_FALLING;
+
+	ret = of_property_read_u32(np, "capella,aset-resistance-ohms", &rset);
+	if (ret) {
+		dev_info(dev, "no RSET specified, assuming 100K\n");
+		rset = 100000;
+	}
+	switch (rset) {
+	case 50000:
+		cm3605->als_max = 650;
+		break;
+	case 100000:
+		cm3605->als_max = 300;
+		break;
+	case 300000:
+		cm3605->als_max = 100;
+		break;
+	case 600000:
+		cm3605->als_max = 50;
+		break;
+	default:
+		dev_info(dev, "non-standard resistance\n");
+		return -EINVAL;
+	}
+
+	cm3605->aout = devm_iio_channel_get(dev, "aout");
+	if (IS_ERR(cm3605->aout)) {
+		if (PTR_ERR(cm3605->aout) == -ENODEV) {
+			dev_err(dev, "no ADC, deferring...\n");
+			return -EPROBE_DEFER;
+		}
+		dev_err(dev, "failed to get AOUT ADC channel\n");
+		return PTR_ERR(cm3605->aout);
+	}
+	ret = iio_get_channel_type(cm3605->aout, &ch_type);
+	if (ret < 0)
+		return ret;
+	if (ch_type != IIO_VOLTAGE) {
+		dev_err(dev, "wrong type of IIO channel specified for AOUT\n");
+		return -EINVAL;
+	}
+
+	cm3605->vdd = devm_regulator_get(dev, "vdd");
+	if (IS_ERR(cm3605->vdd)) {
+		dev_err(dev, "failed to get VDD regulator\n");
+		return PTR_ERR(cm3605->vdd);
+	}
+	ret = regulator_enable(cm3605->vdd);
+	if (ret) {
+		dev_err(dev, "failed to enable VDD regulator\n");
+		return ret;
+	}
+
+	cm3605->aset = devm_gpiod_get(dev, "aset", GPIOD_OUT_HIGH);
+	if (IS_ERR(cm3605->aset)) {
+		dev_err(dev, "no ASET GPIO\n");
+		ret = PTR_ERR(cm3605->aset);
+		goto out_disable_vdd;
+	}
+
+	ret = devm_request_threaded_irq(dev, platform_get_irq(pdev, 0),
+			cm3605_prox_irq, NULL, 0, "cm3605", indio_dev);
+	if (ret) {
+		dev_err(dev, "unable to request IRQ\n");
+		goto out_disable_aset;
+	}
+
+	/* Just name the trigger the same as the driver */
+	led_trigger_register_simple("cm3605", &cm3605->led);
+	led_trigger_event(cm3605->led, LED_FULL);
+
+	indio_dev->dev.parent = dev;
+	indio_dev->info = &cm3605_info;
+	indio_dev->name = "cm3605";
+	indio_dev->channels = cm3605_channels;
+	indio_dev->num_channels = ARRAY_SIZE(cm3605_channels);
+	indio_dev->modes = INDIO_DIRECT_MODE;
+
+	ret = iio_device_register(indio_dev);
+	if (ret)
+		goto out_remove_trigger;
+	dev_info(dev, "Capella Microsystems CM3605 enabled range 0..%d LUX\n",
+		 cm3605->als_max);
+
+	return 0;
+
+out_remove_trigger:
+	led_trigger_event(cm3605->led, LED_OFF);
+	led_trigger_unregister_simple(cm3605->led);
+out_disable_aset:
+	gpiod_set_value_cansleep(cm3605->aset, 0);
+out_disable_vdd:
+	regulator_disable(cm3605->vdd);
+	return ret;
+}
+
+static int cm3605_remove(struct platform_device *pdev)
+{
+	struct iio_dev *indio_dev = platform_get_drvdata(pdev);
+	struct cm3605 *cm3605 = iio_priv(indio_dev);
+
+	led_trigger_event(cm3605->led, LED_OFF);
+	led_trigger_unregister_simple(cm3605->led);
+	gpiod_set_value_cansleep(cm3605->aset, 0);
+	iio_device_unregister(indio_dev);
+	regulator_disable(cm3605->vdd);
+
+	return 0;
+}
+
+static int cm3605_pm_suspend(struct device *dev)
+{
+	struct iio_dev *indio_dev = dev_get_drvdata(dev);
+	struct cm3605 *cm3605 = iio_priv(indio_dev);
+
+	led_trigger_event(cm3605->led, LED_OFF);
+	regulator_disable(cm3605->vdd);
+
+	return 0;
+}
+
+static int cm3605_pm_resume(struct device *dev)
+{
+	struct iio_dev *indio_dev = dev_get_drvdata(dev);
+	struct cm3605 *cm3605 = iio_priv(indio_dev);
+	int ret;
+
+	ret = regulator_enable(cm3605->vdd);
+	if (ret)
+		dev_err(dev, "failed to enable regulator in resume path\n");
+	led_trigger_event(cm3605->led, LED_FULL);
+
+	return 0;
+}
+
+static const struct dev_pm_ops cm3605_dev_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(cm3605_pm_suspend,
+				cm3605_pm_resume)
+};
+
+static const struct of_device_id cm3605_of_match[] = {
+	{.compatible = "capella,cm3605"},
+	{ },
+};
+MODULE_DEVICE_TABLE(of, cm3605_of_match);
+
+static struct platform_driver cm3605_driver = {
+	.driver = {
+		.name = "cm3605",
+		.of_match_table = cm3605_of_match,
+		.pm = &cm3605_dev_pm_ops,
+	},
+	.probe = cm3605_probe,
+	.remove = cm3605_remove,
+};
+module_platform_driver(cm3605_driver);
+
+MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>");
+MODULE_DESCRIPTION("CM3605 ambient light and proximity sensor driver");
+MODULE_LICENSE("GPL");