3 files changed, 173 insertions, 0 deletions

diff --git a/drivers/platform/chrome/Kconfig b/drivers/platform/chrome/Kconfig
index 6b954c5acadb..c1ca247987d2 100644
--- a/drivers/platform/chrome/Kconfig
+++ b/drivers/platform/chrome/Kconfig
@@ -228,6 +228,16 @@ config CROS_EC_TYPEC
 	  To compile this driver as a module, choose M here: the module will be
 	  called cros_ec_typec.
 
+config CROS_HPS_I2C
+	tristate "ChromeOS HPS device"
+	depends on HID && I2C && PM
+	help
+	  Say Y here if you want to enable support for the ChromeOS
+	  human presence sensor (HPS), attached via I2C. The driver supports a
+	  sensor connected to the I2C bus and exposes it as a character device.
+	  To save power, the sensor is automatically powered down when no
+	  clients are accessing it.
+
 config CROS_USBPD_LOGGER
 	tristate "Logging driver for USB PD charger"
 	depends on CHARGER_CROS_USBPD
diff --git a/drivers/platform/chrome/Makefile b/drivers/platform/chrome/Makefile
index 2950610101f1..f6068d077a40 100644
--- a/drivers/platform/chrome/Makefile
+++ b/drivers/platform/chrome/Makefile
@@ -27,6 +27,7 @@ obj-$(CONFIG_CROS_EC_DEBUGFS)		+= cros_ec_debugfs.o
 cros-ec-sensorhub-objs			:= cros_ec_sensorhub.o cros_ec_sensorhub_ring.o
 obj-$(CONFIG_CROS_EC_SENSORHUB)		+= cros-ec-sensorhub.o
 obj-$(CONFIG_CROS_EC_SYSFS)		+= cros_ec_sysfs.o
+obj-$(CONFIG_CROS_HPS_I2C)		+= cros_hps_i2c.o
 obj-$(CONFIG_CROS_USBPD_LOGGER)		+= cros_usbpd_logger.o
 obj-$(CONFIG_CROS_USBPD_NOTIFY)		+= cros_usbpd_notify.o
 
diff --git a/drivers/platform/chrome/cros_hps_i2c.c b/drivers/platform/chrome/cros_hps_i2c.c
new file mode 100644
index 000000000000..92da59d94745
--- /dev/null
+++ b/drivers/platform/chrome/cros_hps_i2c.c
@@ -0,0 +1,162 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Driver for the ChromeOS human presence sensor (HPS), attached via I2C.
+ *
+ * The driver exposes HPS as a character device, although currently no read or
+ * write operations are supported. Instead, the driver only controls the power
+ * state of the sensor, keeping it on only while userspace holds an open file
+ * descriptor to the HPS device.
+ *
+ * Copyright 2022 Google LLC.
+ */
+
+#include <linux/acpi.h>
+#include <linux/fs.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/pm_runtime.h>
+
+#define HPS_ACPI_ID		"GOOG0020"
+
+struct hps_drvdata {
+	struct i2c_client *client;
+	struct miscdevice misc_device;
+	struct gpio_desc *enable_gpio;
+};
+
+static void hps_set_power(struct hps_drvdata *hps, bool state)
+{
+	gpiod_set_value_cansleep(hps->enable_gpio, state);
+}
+
+static int hps_open(struct inode *inode, struct file *file)
+{
+	struct hps_drvdata *hps = container_of(file->private_data,
+					       struct hps_drvdata, misc_device);
+	struct device *dev = &hps->client->dev;
+
+	return pm_runtime_resume_and_get(dev);
+}
+
+static int hps_release(struct inode *inode, struct file *file)
+{
+	struct hps_drvdata *hps = container_of(file->private_data,
+					       struct hps_drvdata, misc_device);
+	struct device *dev = &hps->client->dev;
+
+	return pm_runtime_put(dev);
+}
+
+static const struct file_operations hps_fops = {
+	.owner = THIS_MODULE,
+	.open = hps_open,
+	.release = hps_release,
+};
+
+static int hps_i2c_probe(struct i2c_client *client)
+{
+	struct hps_drvdata *hps;
+	int ret;
+
+	hps = devm_kzalloc(&client->dev, sizeof(*hps), GFP_KERNEL);
+	if (!hps)
+		return -ENOMEM;
+
+	hps->misc_device.parent = &client->dev;
+	hps->misc_device.minor = MISC_DYNAMIC_MINOR;
+	hps->misc_device.name = "cros-hps";
+	hps->misc_device.fops = &hps_fops;
+
+	i2c_set_clientdata(client, hps);
+	hps->client = client;
+
+	/*
+	 * HPS is powered on from firmware before entering the kernel, so we
+	 * acquire the line with GPIOD_OUT_HIGH here to preserve the existing
+	 * state. The peripheral is powered off after successful probe below.
+	 */
+	hps->enable_gpio = devm_gpiod_get(&client->dev, "enable", GPIOD_OUT_HIGH);
+	if (IS_ERR(hps->enable_gpio)) {
+		ret = PTR_ERR(hps->enable_gpio);
+		dev_err(&client->dev, "failed to get enable gpio: %d\n", ret);
+		return ret;
+	}
+
+	ret = misc_register(&hps->misc_device);
+	if (ret) {
+		dev_err(&client->dev, "failed to initialize misc device: %d\n", ret);
+		return ret;
+	}
+
+	hps_set_power(hps, false);
+	pm_runtime_enable(&client->dev);
+	return 0;
+}
+
+static int hps_i2c_remove(struct i2c_client *client)
+{
+	struct hps_drvdata *hps = i2c_get_clientdata(client);
+
+	pm_runtime_disable(&client->dev);
+	misc_deregister(&hps->misc_device);
+
+	/*
+	 * Re-enable HPS, in order to return it to its default state
+	 * (i.e. powered on).
+	 */
+	hps_set_power(hps, true);
+
+	return 0;
+}
+
+static int hps_suspend(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct hps_drvdata *hps = i2c_get_clientdata(client);
+
+	hps_set_power(hps, false);
+	return 0;
+}
+
+static int hps_resume(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct hps_drvdata *hps = i2c_get_clientdata(client);
+
+	hps_set_power(hps, true);
+	return 0;
+}
+static UNIVERSAL_DEV_PM_OPS(hps_pm_ops, hps_suspend, hps_resume, NULL);
+
+static const struct i2c_device_id hps_i2c_id[] = {
+	{ "cros-hps", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, hps_i2c_id);
+
+#ifdef CONFIG_ACPI
+static const struct acpi_device_id hps_acpi_id[] = {
+	{ HPS_ACPI_ID, 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(acpi, hps_acpi_id);
+#endif /* CONFIG_ACPI */
+
+static struct i2c_driver hps_i2c_driver = {
+	.probe_new = hps_i2c_probe,
+	.remove = hps_i2c_remove,
+	.id_table = hps_i2c_id,
+	.driver = {
+		.name = "cros-hps",
+		.pm = &hps_pm_ops,
+		.acpi_match_table = ACPI_PTR(hps_acpi_id),
+	},
+};
+module_i2c_driver(hps_i2c_driver);
+
+MODULE_ALIAS("acpi:" HPS_ACPI_ID);
+MODULE_AUTHOR("Sami Kyöstilä <skyostil@chromium.org>");
+MODULE_DESCRIPTION("Driver for ChromeOS HPS");
+MODULE_LICENSE("GPL");