usb: misc: Add onboard_usb_hub driver

The main issue this driver addresses is that a USB hub needs to be
powered before it can be discovered. For discrete onboard hubs (an
example for such a hub is the Realtek RTS5411) this is often solved
by supplying the hub with an 'always-on' regulator, which is kind
of a hack. Some onboard hubs may require further initialization
steps, like changing the state of a GPIO or enabling a clock, which
requires even more hacks. This driver creates a platform device
representing the hub which performs the necessary initialization.
Currently it only supports switching on a single regulator, support
for multiple regulators or other actions can be added as needed.
Different initialization sequences can be supported based on the
compatible string.

Besides performing the initialization the driver can be configured
to power the hub off during system suspend. This can help to extend
battery life on battery powered devices which have no requirements
to keep the hub powered during suspend. The driver can also be
configured to leave the hub powered when a wakeup capable USB device
is connected when suspending, and power it off otherwise.

Technically the driver consists of two drivers, the platform driver
described above and a very thin USB driver that subclasses the
generic driver. The purpose of this driver is to provide the platform
driver with the USB devices corresponding to the hub(s) (a hub
controller may provide multiple 'logical' hubs, e.g. one to support
USB 2.0 and another for USB 3.x).

Co-developed-by: Ravi Chandra Sadineni <ravisadineni@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Ravi Chandra Sadineni <ravisadineni@chromium.org>
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Link: https://lore.kernel.org/r/20220630123445.v24.3.I7c9a1f1d6ced41dd8310e8a03da666a32364e790@changeid
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 428 insertions, 0 deletions

diff --git a/drivers/usb/misc/onboard_usb_hub.c b/drivers/usb/misc/onboard_usb_hub.c
new file mode 100644
index 000000000000..6b9b949d17d3
--- /dev/null
+++ b/drivers/usb/misc/onboard_usb_hub.c
@@ -0,0 +1,428 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Driver for onboard USB hubs
+ *
+ * Copyright (c) 2022, Google LLC
+ */
+
+#include <linux/device.h>
+#include <linux/export.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/regulator/consumer.h>
+#include <linux/slab.h>
+#include <linux/suspend.h>
+#include <linux/sysfs.h>
+#include <linux/usb.h>
+#include <linux/usb/hcd.h>
+#include <linux/usb/onboard_hub.h>
+#include <linux/workqueue.h>
+
+#include "onboard_usb_hub.h"
+
+static struct usb_device_driver onboard_hub_usbdev_driver;
+
+/************************** Platform driver **************************/
+
+struct usbdev_node {
+	struct usb_device *udev;
+	struct list_head list;
+};
+
+struct onboard_hub {
+	struct regulator *vdd;
+	struct device *dev;
+	bool always_powered_in_suspend;
+	bool is_powered_on;
+	bool going_away;
+	struct list_head udev_list;
+	struct work_struct attach_usb_driver_work;
+	struct mutex lock;
+};
+
+static int onboard_hub_power_on(struct onboard_hub *hub)
+{
+	int err;
+
+	err = regulator_enable(hub->vdd);
+	if (err) {
+		dev_err(hub->dev, "failed to enable regulator: %d\n", err);
+		return err;
+	}
+
+	hub->is_powered_on = true;
+
+	return 0;
+}
+
+static int onboard_hub_power_off(struct onboard_hub *hub)
+{
+	int err;
+
+	err = regulator_disable(hub->vdd);
+	if (err) {
+		dev_err(hub->dev, "failed to disable regulator: %d\n", err);
+		return err;
+	}
+
+	hub->is_powered_on = false;
+
+	return 0;
+}
+
+static int __maybe_unused onboard_hub_suspend(struct device *dev)
+{
+	struct onboard_hub *hub = dev_get_drvdata(dev);
+	struct usbdev_node *node;
+	bool power_off = true;
+
+	if (hub->always_powered_in_suspend)
+		return 0;
+
+	mutex_lock(&hub->lock);
+
+	list_for_each_entry(node, &hub->udev_list, list) {
+		if (!device_may_wakeup(node->udev->bus->controller))
+			continue;
+
+		if (usb_wakeup_enabled_descendants(node->udev)) {
+			power_off = false;
+			break;
+		}
+	}
+
+	mutex_unlock(&hub->lock);
+
+	if (!power_off)
+		return 0;
+
+	return onboard_hub_power_off(hub);
+}
+
+static int __maybe_unused onboard_hub_resume(struct device *dev)
+{
+	struct onboard_hub *hub = dev_get_drvdata(dev);
+
+	if (hub->is_powered_on)
+		return 0;
+
+	return onboard_hub_power_on(hub);
+}
+
+static inline void get_udev_link_name(const struct usb_device *udev, char *buf, size_t size)
+{
+	snprintf(buf, size, "usb_dev.%s", dev_name(&udev->dev));
+}
+
+static int onboard_hub_add_usbdev(struct onboard_hub *hub, struct usb_device *udev)
+{
+	struct usbdev_node *node;
+	char link_name[64];
+	int err;
+
+	mutex_lock(&hub->lock);
+
+	if (hub->going_away) {
+		err = -EINVAL;
+		goto error;
+	}
+
+	node = kzalloc(sizeof(*node), GFP_KERNEL);
+	if (!node) {
+		err = -ENOMEM;
+		goto error;
+	}
+
+	node->udev = udev;
+
+	list_add(&node->list, &hub->udev_list);
+
+	mutex_unlock(&hub->lock);
+
+	get_udev_link_name(udev, link_name, sizeof(link_name));
+	WARN_ON(sysfs_create_link(&hub->dev->kobj, &udev->dev.kobj, link_name));
+
+	return 0;
+
+error:
+	mutex_unlock(&hub->lock);
+
+	return err;
+}
+
+static void onboard_hub_remove_usbdev(struct onboard_hub *hub, const struct usb_device *udev)
+{
+	struct usbdev_node *node;
+	char link_name[64];
+
+	get_udev_link_name(udev, link_name, sizeof(link_name));
+	sysfs_remove_link(&hub->dev->kobj, link_name);
+
+	mutex_lock(&hub->lock);
+
+	list_for_each_entry(node, &hub->udev_list, list) {
+		if (node->udev == udev) {
+			list_del(&node->list);
+			kfree(node);
+			break;
+		}
+	}
+
+	mutex_unlock(&hub->lock);
+}
+
+static ssize_t always_powered_in_suspend_show(struct device *dev, struct device_attribute *attr,
+			   char *buf)
+{
+	const struct onboard_hub *hub = dev_get_drvdata(dev);
+
+	return sysfs_emit(buf, "%d\n", hub->always_powered_in_suspend);
+}
+
+static ssize_t always_powered_in_suspend_store(struct device *dev, struct device_attribute *attr,
+			    const char *buf, size_t count)
+{
+	struct onboard_hub *hub = dev_get_drvdata(dev);
+	bool val;
+	int ret;
+
+	ret = kstrtobool(buf, &val);
+	if (ret < 0)
+		return ret;
+
+	hub->always_powered_in_suspend = val;
+
+	return count;
+}
+static DEVICE_ATTR_RW(always_powered_in_suspend);
+
+static struct attribute *onboard_hub_attrs[] = {
+	&dev_attr_always_powered_in_suspend.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(onboard_hub);
+
+static void onboard_hub_attach_usb_driver(struct work_struct *work)
+{
+	int err;
+
+	err = driver_attach(&onboard_hub_usbdev_driver.drvwrap.driver);
+	if (err)
+		pr_err("Failed to attach USB driver: %d\n", err);
+}
+
+static int onboard_hub_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct onboard_hub *hub;
+	int err;
+
+	hub = devm_kzalloc(dev, sizeof(*hub), GFP_KERNEL);
+	if (!hub)
+		return -ENOMEM;
+
+	hub->vdd = devm_regulator_get(dev, "vdd");
+	if (IS_ERR(hub->vdd))
+		return PTR_ERR(hub->vdd);
+
+	hub->dev = dev;
+	mutex_init(&hub->lock);
+	INIT_LIST_HEAD(&hub->udev_list);
+
+	dev_set_drvdata(dev, hub);
+
+	err = onboard_hub_power_on(hub);
+	if (err)
+		return err;
+
+	/*
+	 * The USB driver might have been detached from the USB devices by
+	 * onboard_hub_remove() (e.g. through an 'unbind' by userspace),
+	 * make sure to re-attach it if needed.
+	 *
+	 * This needs to be done deferred to avoid self-deadlocks on systems
+	 * with nested onboard hubs.
+	 */
+	INIT_WORK(&hub->attach_usb_driver_work, onboard_hub_attach_usb_driver);
+	schedule_work(&hub->attach_usb_driver_work);
+
+	return 0;
+}
+
+static int onboard_hub_remove(struct platform_device *pdev)
+{
+	struct onboard_hub *hub = dev_get_drvdata(&pdev->dev);
+	struct usbdev_node *node;
+	struct usb_device *udev;
+
+	hub->going_away = true;
+
+	if (&hub->attach_usb_driver_work != current_work())
+		cancel_work_sync(&hub->attach_usb_driver_work);
+
+	mutex_lock(&hub->lock);
+
+	/* unbind the USB devices to avoid dangling references to this device */
+	while (!list_empty(&hub->udev_list)) {
+		node = list_first_entry(&hub->udev_list, struct usbdev_node, list);
+		udev = node->udev;
+
+		/*
+		 * Unbinding the driver will call onboard_hub_remove_usbdev(),
+		 * which acquires hub->lock.  We must release the lock first.
+		 */
+		get_device(&udev->dev);
+		mutex_unlock(&hub->lock);
+		device_release_driver(&udev->dev);
+		put_device(&udev->dev);
+		mutex_lock(&hub->lock);
+	}
+
+	mutex_unlock(&hub->lock);
+
+	return onboard_hub_power_off(hub);
+}
+
+MODULE_DEVICE_TABLE(of, onboard_hub_match);
+
+static const struct dev_pm_ops __maybe_unused onboard_hub_pm_ops = {
+	SET_LATE_SYSTEM_SLEEP_PM_OPS(onboard_hub_suspend, onboard_hub_resume)
+};
+
+static struct platform_driver onboard_hub_driver = {
+	.probe = onboard_hub_probe,
+	.remove = onboard_hub_remove,
+
+	.driver = {
+		.name = "onboard-usb-hub",
+		.of_match_table = onboard_hub_match,
+		.pm = pm_ptr(&onboard_hub_pm_ops),
+		.dev_groups = onboard_hub_groups,
+	},
+};
+
+/************************** USB driver **************************/
+
+#define VENDOR_ID_REALTEK	0x0bda
+
+/*
+ * Returns the onboard_hub platform device that is associated with the USB
+ * device passed as parameter.
+ */
+static struct onboard_hub *_find_onboard_hub(struct device *dev)
+{
+	struct platform_device *pdev;
+	struct device_node *np;
+	struct onboard_hub *hub;
+
+	pdev = of_find_device_by_node(dev->of_node);
+	if (!pdev) {
+		np = of_parse_phandle(dev->of_node, "peer-hub", 0);
+		if (!np) {
+			dev_err(dev, "failed to find device node for peer hub\n");
+			return ERR_PTR(-EINVAL);
+		}
+
+		pdev = of_find_device_by_node(np);
+		of_node_put(np);
+
+		if (!pdev)
+			return ERR_PTR(-ENODEV);
+	}
+
+	hub = dev_get_drvdata(&pdev->dev);
+	put_device(&pdev->dev);
+
+	/*
+	 * The presence of drvdata ('hub') indicates that the platform driver
+	 * finished probing. This handles the case where (conceivably) we could
+	 * be running at the exact same time as the platform driver's probe. If
+	 * we detect the race we request probe deferral and we'll come back and
+	 * try again.
+	 */
+	if (!hub)
+		return ERR_PTR(-EPROBE_DEFER);
+
+	return hub;
+}
+
+static int onboard_hub_usbdev_probe(struct usb_device *udev)
+{
+	struct device *dev = &udev->dev;
+	struct onboard_hub *hub;
+	int err;
+
+	/* ignore supported hubs without device tree node */
+	if (!dev->of_node)
+		return -ENODEV;
+
+	hub = _find_onboard_hub(dev);
+	if (IS_ERR(hub))
+		return PTR_ERR(hub);
+
+	dev_set_drvdata(dev, hub);
+
+	err = onboard_hub_add_usbdev(hub, udev);
+	if (err)
+		return err;
+
+	return 0;
+}
+
+static void onboard_hub_usbdev_disconnect(struct usb_device *udev)
+{
+	struct onboard_hub *hub = dev_get_drvdata(&udev->dev);
+
+	onboard_hub_remove_usbdev(hub, udev);
+}
+
+static const struct usb_device_id onboard_hub_id_table[] = {
+	{ USB_DEVICE(VENDOR_ID_REALTEK, 0x0411) }, /* RTS5411 USB 3.1 */
+	{ USB_DEVICE(VENDOR_ID_REALTEK, 0x5411) }, /* RTS5411 USB 2.1 */
+	{ USB_DEVICE(VENDOR_ID_REALTEK, 0x0414) }, /* RTS5414 USB 3.2 */
+	{ USB_DEVICE(VENDOR_ID_REALTEK, 0x5414) }, /* RTS5414 USB 2.1 */
+	{}
+};
+MODULE_DEVICE_TABLE(usb, onboard_hub_id_table);
+
+static struct usb_device_driver onboard_hub_usbdev_driver = {
+	.name = "onboard-usb-hub",
+	.probe = onboard_hub_usbdev_probe,
+	.disconnect = onboard_hub_usbdev_disconnect,
+	.generic_subclass = 1,
+	.supports_autosuspend =	1,
+	.id_table = onboard_hub_id_table,
+};
+
+static int __init onboard_hub_init(void)
+{
+	int ret;
+
+	ret = platform_driver_register(&onboard_hub_driver);
+	if (ret)
+		return ret;
+
+	ret = usb_register_device_driver(&onboard_hub_usbdev_driver, THIS_MODULE);
+	if (ret)
+		platform_driver_unregister(&onboard_hub_driver);
+
+	return ret;
+}
+module_init(onboard_hub_init);
+
+static void __exit onboard_hub_exit(void)
+{
+	usb_deregister_device_driver(&onboard_hub_usbdev_driver);
+	platform_driver_unregister(&onboard_hub_driver);
+}
+module_exit(onboard_hub_exit);
+
+MODULE_AUTHOR("Matthias Kaehlcke <mka@chromium.org>");
+MODULE_DESCRIPTION("Driver for discrete onboard USB hubs");
+MODULE_LICENSE("GPL v2");