iio: proximity: Add a ChromeOS EC MKBP proximity driver

Add support for a ChromeOS EC proximity driver that exposes a "front"
proximity sensor via the IIO subsystem. The EC decides when front
proximity is near and sets an MKBP switch 'EC_MKBP_FRONT_PROXIMITY' to
notify the kernel of proximity. Similarly, when proximity detects
something far away it sets the switch bit to 0. For now this driver
exposes a single sensor, but it could be expanded in the future via more
MKBP bits if desired.

Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Benson Leung <bleung@chromium.org>
Cc: Guenter Roeck <groeck@chromium.org>
Cc: Douglas Anderson <dianders@chromium.org>
Cc: Gwendal Grignou <gwendal@chromium.org>
Reviewed-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Gwendal Grignou <gwendal@chromium.org>
Link: https://lore.kernel.org/r/20210211024601.1963379-4-swboyd@chromium.org
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/proximity/Kconfig

@@ -21,6 +21,17 @@ endmenu
 
 menu "Proximity and distance sensors"
 
+config CROS_EC_MKBP_PROXIMITY
+	tristate "ChromeOS EC MKBP Proximity sensor"
+	depends on CROS_EC
+	help
+	  Say Y here to enable the proximity sensor implemented via the ChromeOS EC MKBP
+	  switches protocol. You must enable one bus option (CROS_EC_I2C or CROS_EC_SPI)
+	  to use this.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called cros_ec_mkbp_proximity.
+
 config ISL29501
 	tristate "Intersil ISL29501 Time Of Flight sensor"
 	depends on I2C

drivers/iio/proximity/Makefile

@@ -5,6 +5,7 @@
 
 # When adding new entries keep the list in alphabetical order
 obj-$(CONFIG_AS3935)		+= as3935.o
+obj-$(CONFIG_CROS_EC_MKBP_PROXIMITY) += cros_ec_mkbp_proximity.o
 obj-$(CONFIG_ISL29501)		+= isl29501.o
 obj-$(CONFIG_LIDAR_LITE_V2)	+= pulsedlight-lidar-lite-v2.o
 obj-$(CONFIG_MB1232)		+= mb1232.o

drivers/iio/proximity/cros_ec_mkbp_proximity.c

@@ -0,0 +1,271 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Driver for cros-ec proximity sensor exposed through MKBP switch
+ *
+ * Copyright 2021 Google LLC.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/notifier.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+
+#include <linux/platform_data/cros_ec_commands.h>
+#include <linux/platform_data/cros_ec_proto.h>
+
+#include <linux/iio/events.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+
+#include <asm/unaligned.h>
+
+struct cros_ec_mkbp_proximity_data {
+	struct cros_ec_device *ec;
+	struct iio_dev *indio_dev;
+	struct mutex lock;
+	struct notifier_block notifier;
+	int last_proximity;
+	bool enabled;
+};
+
+static const struct iio_event_spec cros_ec_mkbp_proximity_events[] = {
+	{
+		.type = IIO_EV_TYPE_THRESH,
+		.dir = IIO_EV_DIR_EITHER,
+		.mask_separate = BIT(IIO_EV_INFO_ENABLE),
+	},
+};
+
+static const struct iio_chan_spec cros_ec_mkbp_proximity_chan_spec[] = {
+	{
+		.type = IIO_PROXIMITY,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
+		.event_spec = cros_ec_mkbp_proximity_events,
+		.num_event_specs = ARRAY_SIZE(cros_ec_mkbp_proximity_events),
+	},
+};
+
+static int cros_ec_mkbp_proximity_parse_state(const void *data)
+{
+	u32 switches = get_unaligned_le32(data);
+
+	return !!(switches & BIT(EC_MKBP_FRONT_PROXIMITY));
+}
+
+static int cros_ec_mkbp_proximity_query(struct cros_ec_device *ec_dev,
+					int *state)
+{
+	struct {
+		struct cros_ec_command msg;
+		union {
+			struct ec_params_mkbp_info params;
+			u32 switches;
+		};
+	} __packed buf = { };
+	struct ec_params_mkbp_info *params = &buf.params;
+	struct cros_ec_command *msg = &buf.msg;
+	u32 *switches = &buf.switches;
+	size_t insize = sizeof(*switches);
+	int ret;
+
+	msg->command = EC_CMD_MKBP_INFO;
+	msg->version = 1;
+	msg->outsize = sizeof(*params);
+	msg->insize = insize;
+
+	params->info_type = EC_MKBP_INFO_CURRENT;
+	params->event_type = EC_MKBP_EVENT_SWITCH;
+
+	ret = cros_ec_cmd_xfer_status(ec_dev, msg);
+	if (ret < 0)
+		return ret;
+
+	if (ret != insize) {
+		dev_warn(ec_dev->dev, "wrong result size: %d != %zu\n", ret,
+			 insize);
+		return -EPROTO;
+	}
+
+	*state = cros_ec_mkbp_proximity_parse_state(switches);
+	return IIO_VAL_INT;
+}
+
+static void cros_ec_mkbp_proximity_push_event(struct cros_ec_mkbp_proximity_data *data, int state)
+{
+	s64 timestamp;
+	u64 ev;
+	int dir;
+	struct iio_dev *indio_dev = data->indio_dev;
+	struct cros_ec_device *ec = data->ec;
+
+	mutex_lock(&data->lock);
+	if (state != data->last_proximity) {
+		if (data->enabled) {
+			timestamp = ktime_to_ns(ec->last_event_time);
+			if (iio_device_get_clock(indio_dev) != CLOCK_BOOTTIME)
+				timestamp = iio_get_time_ns(indio_dev);
+
+			dir = state ? IIO_EV_DIR_FALLING : IIO_EV_DIR_RISING;
+			ev = IIO_UNMOD_EVENT_CODE(IIO_PROXIMITY, 0,
+						  IIO_EV_TYPE_THRESH, dir);
+			iio_push_event(indio_dev, ev, timestamp);
+		}
+		data->last_proximity = state;
+	}
+	mutex_unlock(&data->lock);
+}
+
+static int cros_ec_mkbp_proximity_notify(struct notifier_block *nb,
+					 unsigned long queued_during_suspend,
+					 void *_ec)
+{
+	struct cros_ec_mkbp_proximity_data *data;
+	struct cros_ec_device *ec = _ec;
+	u8 event_type = ec->event_data.event_type & EC_MKBP_EVENT_TYPE_MASK;
+	void *switches;
+	int state;
+
+	if (event_type == EC_MKBP_EVENT_SWITCH) {
+		data = container_of(nb, struct cros_ec_mkbp_proximity_data,
+				    notifier);
+
+		switches = &ec->event_data.data.switches;
+		state = cros_ec_mkbp_proximity_parse_state(switches);
+		cros_ec_mkbp_proximity_push_event(data, state);
+	}
+
+	return NOTIFY_OK;
+}
+
+static int cros_ec_mkbp_proximity_read_raw(struct iio_dev *indio_dev,
+			   const struct iio_chan_spec *chan, int *val,
+			   int *val2, long mask)
+{
+	struct cros_ec_mkbp_proximity_data *data = iio_priv(indio_dev);
+	struct cros_ec_device *ec = data->ec;
+
+	if (chan->type == IIO_PROXIMITY && mask == IIO_CHAN_INFO_RAW)
+		return cros_ec_mkbp_proximity_query(ec, val);
+
+	return -EINVAL;
+}
+
+static int cros_ec_mkbp_proximity_read_event_config(struct iio_dev *indio_dev,
+				    const struct iio_chan_spec *chan,
+				    enum iio_event_type type,
+				    enum iio_event_direction dir)
+{
+	struct cros_ec_mkbp_proximity_data *data = iio_priv(indio_dev);
+
+	return data->enabled;
+}
+
+static int cros_ec_mkbp_proximity_write_event_config(struct iio_dev *indio_dev,
+				     const struct iio_chan_spec *chan,
+				     enum iio_event_type type,
+				     enum iio_event_direction dir, int state)
+{
+	struct cros_ec_mkbp_proximity_data *data = iio_priv(indio_dev);
+
+	mutex_lock(&data->lock);
+	data->enabled = state;
+	mutex_unlock(&data->lock);
+
+	return 0;
+}
+
+static const struct iio_info cros_ec_mkbp_proximity_info = {
+	.read_raw = cros_ec_mkbp_proximity_read_raw,
+	.read_event_config = cros_ec_mkbp_proximity_read_event_config,
+	.write_event_config = cros_ec_mkbp_proximity_write_event_config,
+};
+
+static __maybe_unused int cros_ec_mkbp_proximity_resume(struct device *dev)
+{
+	struct cros_ec_mkbp_proximity_data *data = dev_get_drvdata(dev);
+	struct cros_ec_device *ec = data->ec;
+	int ret, state;
+
+	ret = cros_ec_mkbp_proximity_query(ec, &state);
+	if (ret < 0) {
+		dev_warn(dev, "failed to fetch proximity state on resume: %d\n",
+			 ret);
+	} else {
+		cros_ec_mkbp_proximity_push_event(data, state);
+	}
+
+	return 0;
+}
+
+static SIMPLE_DEV_PM_OPS(cros_ec_mkbp_proximity_pm_ops, NULL,
+			 cros_ec_mkbp_proximity_resume);
+
+static int cros_ec_mkbp_proximity_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct cros_ec_device *ec = dev_get_drvdata(dev->parent);
+	struct iio_dev *indio_dev;
+	struct cros_ec_mkbp_proximity_data *data;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	data = iio_priv(indio_dev);
+	data->ec = ec;
+	data->indio_dev = indio_dev;
+	data->last_proximity = -1; /* Unknown to start */
+	mutex_init(&data->lock);
+	platform_set_drvdata(pdev, data);
+
+	indio_dev->name = dev->driver->name;
+	indio_dev->info = &cros_ec_mkbp_proximity_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = cros_ec_mkbp_proximity_chan_spec;
+	indio_dev->num_channels = ARRAY_SIZE(cros_ec_mkbp_proximity_chan_spec);
+
+	ret = devm_iio_device_register(dev, indio_dev);
+	if (ret)
+		return ret;
+
+	data->notifier.notifier_call = cros_ec_mkbp_proximity_notify;
+	blocking_notifier_chain_register(&ec->event_notifier, &data->notifier);
+
+	return 0;
+}
+
+static int cros_ec_mkbp_proximity_remove(struct platform_device *pdev)
+{
+	struct cros_ec_mkbp_proximity_data *data = platform_get_drvdata(pdev);
+	struct cros_ec_device *ec = data->ec;
+
+	blocking_notifier_chain_unregister(&ec->event_notifier,
+					   &data->notifier);
+
+	return 0;
+}
+
+static const struct of_device_id cros_ec_mkbp_proximity_of_match[] = {
+	{ .compatible = "google,cros-ec-mkbp-proximity" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, cros_ec_mkbp_proximity_of_match);
+
+static struct platform_driver cros_ec_mkbp_proximity_driver = {
+	.driver = {
+		.name = "cros-ec-mkbp-proximity",
+		.of_match_table = cros_ec_mkbp_proximity_of_match,
+		.pm = &cros_ec_mkbp_proximity_pm_ops,
+	},
+	.probe = cros_ec_mkbp_proximity_probe,
+	.remove = cros_ec_mkbp_proximity_remove,
+};
+module_platform_driver(cros_ec_mkbp_proximity_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("ChromeOS EC MKBP proximity sensor driver");