| Message ID | 20200923180952.v3.2.I7c9a1f1d6ced41dd8310e8a03da666a32364e790@changeid (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [v3,1/2] dt-bindings: usb: Add binding for discrete onboard USB hubs | expand |
On Wed, Sep 23, 2020 at 06:10:12PM -0700, Matthias Kaehlcke wrote: > 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> > Signed-off-by: Ravi Chandra Sadineni <ravisadineni@chromium.org> > Signed-off-by: Matthias Kaehlcke <mka@chromium.org> > --- > --- a/drivers/usb/misc/Kconfig > +++ b/drivers/usb/misc/Kconfig > @@ -275,3 +275,19 @@ config USB_CHAOSKEY > > To compile this driver as a module, choose M here: the > module will be called chaoskey. > + > +config USB_ONBOARD_HUB > + tristate "Onboard USB hub support" > + depends on OF || COMPILE_TEST > + help > + Say Y here if you want to support discrete onboard USB hubs that > + don't require an additional control bus for initialization (an ... but does require nontrivial form of initialization, such as enabling a power regulator. > +static void onboard_hub_remove_usbdev(struct onboard_hub *hub, struct usb_device *udev) > +{ > + struct udev_node *node; > + > + smp_rmb(); > + if (hub->going_away) { > + /* > + * We are most likely being called as a result of unbinding a USB device from > + * onboard_hub_remove(). This function also holds the lock and iterates over > + * 'udev_list'. Skip deleting the node in this case to avoid a self deadlock, > + * keeping the node in the list isn't a problem, since the device is about to go > + * away. > + */ > + return; > + } This part has a suspicious look. For one thing, there's no comment explaining the purpose of the smp_rmb(). For another, that barrier doesn't seem to pair with any other memory barrier in the driver. I get that you want to avoid self-deadlock here. But there must be a better way. See below. > +static int onboard_hub_remove(struct platform_device *pdev) > +{ > + struct onboard_hub *hub = dev_get_drvdata(&pdev->dev); > + struct udev_node *node; > + > + hub->going_away = true; > + > + mutex_lock(&hub->lock); > + > + /* unbind the USB devices to avoid dangling references to this device */ > + list_for_each_entry(node, &hub->udev_list, list) > + device_release_driver(&node->udev->dev); > + > + mutex_unlock(&hub->lock); Alternative approach: /* unbind the USB devices to avoid dangling references to this device */ mutex_lock(&hub->lock); while (!list_empty(&hub->udev_list)) { node = list_first_entry(&hub->udev_list, struct udev_node, list); udev = node->udev; /* * Unbinding the driver will call onboard_hub_remove_usbdev(), * which acquires hub->lock. We must release the lock first. */ usb_get_device(udev); mutex_unlock(&hub->lock); device_release_driver(&udev->dev); usb_put_device(udev); mutex_lock(&hub->lock); } mutex_unlock(&hub->lock); > +static int onboard_hub_usbdev_probe(struct usb_device *udev) > +{ > + struct device *dev = &udev->dev; > + struct onboard_hub *hub; > + > + /* 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(dev); hub, not dev. Alan Stern
Hi Alan, On Thu, Sep 24, 2020 at 11:27:58AM -0400, Alan Stern wrote: > On Wed, Sep 23, 2020 at 06:10:12PM -0700, Matthias Kaehlcke wrote: > > 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> > > Signed-off-by: Ravi Chandra Sadineni <ravisadineni@chromium.org> > > Signed-off-by: Matthias Kaehlcke <mka@chromium.org> > > --- > > > --- a/drivers/usb/misc/Kconfig > > +++ b/drivers/usb/misc/Kconfig > > @@ -275,3 +275,19 @@ config USB_CHAOSKEY > > > > To compile this driver as a module, choose M here: the > > module will be called chaoskey. > > + > > +config USB_ONBOARD_HUB > > + tristate "Onboard USB hub support" > > + depends on OF || COMPILE_TEST > > + help > > + Say Y here if you want to support discrete onboard USB hubs that > > + don't require an additional control bus for initialization (an > > ... but does require nontrivial form of initialization, such as > enabling a power regulator. ok, I'll add that > > +static void onboard_hub_remove_usbdev(struct onboard_hub *hub, struct usb_device *udev) > > +{ > > + struct udev_node *node; > > + > > + smp_rmb(); > > + if (hub->going_away) { > > + /* > > + * We are most likely being called as a result of unbinding a USB device from > > + * onboard_hub_remove(). This function also holds the lock and iterates over > > + * 'udev_list'. Skip deleting the node in this case to avoid a self deadlock, > > + * keeping the node in the list isn't a problem, since the device is about to go > > + * away. > > + */ > > + return; > > + } > > This part has a suspicious look. For one thing, there's no comment > explaining the purpose of the smp_rmb(). For another, that barrier > doesn't seem to pair with any other memory barrier in the driver. IIUC the mutex_lock() in onboard_hub_remove() is an implicit barrier, but it is indeed not obvious from looking at the code. > I get that you want to avoid self-deadlock here. But there must be a > better way. See below. I wasn't super happy about this either ... > > +static int onboard_hub_remove(struct platform_device *pdev) > > +{ > > + struct onboard_hub *hub = dev_get_drvdata(&pdev->dev); > > + struct udev_node *node; > > + > > + hub->going_away = true; > > + > > + mutex_lock(&hub->lock); > > + > > + /* unbind the USB devices to avoid dangling references to this device */ > > + list_for_each_entry(node, &hub->udev_list, list) > > + device_release_driver(&node->udev->dev); > > + > > + mutex_unlock(&hub->lock); > > Alternative approach: > > /* unbind the USB devices to avoid dangling references to this device */ > mutex_lock(&hub->lock); > while (!list_empty(&hub->udev_list)) { > node = list_first_entry(&hub->udev_list, struct udev_node, list); > udev = node->udev; > > /* > * Unbinding the driver will call onboard_hub_remove_usbdev(), > * which acquires hub->lock. We must release the lock first. > */ > usb_get_device(udev); > mutex_unlock(&hub->lock); > device_release_driver(&udev->dev); > usb_put_device(udev); > mutex_lock(&hub->lock); > } > mutex_unlock(&hub->lock); > Thanks, that should work. I also thought about unlocking the mutex before calling device_release_driver(), but that wouldn't be the right thing when using list_for_each_entry(_safe). The alternative loop style allows for it. > > +static int onboard_hub_usbdev_probe(struct usb_device *udev) > > +{ > > + struct device *dev = &udev->dev; > > + struct onboard_hub *hub; > > + > > + /* 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(dev); > > hub, not dev. ugh, yes
diff --git a/drivers/usb/misc/Kconfig b/drivers/usb/misc/Kconfig index 6818ea689cd9..df470903848c 100644 --- a/drivers/usb/misc/Kconfig +++ b/drivers/usb/misc/Kconfig @@ -275,3 +275,19 @@ config USB_CHAOSKEY To compile this driver as a module, choose M here: the module will be called chaoskey. + +config USB_ONBOARD_HUB + tristate "Onboard USB hub support" + depends on OF || COMPILE_TEST + help + Say Y here if you want to support discrete onboard USB hubs that + don't require an additional control bus for initialization (an + example for such a hub is the Realtek RTS5411). The driver powers + supported hubs on and may perform other initialization steps. + + The driver can be configured to turn off the power of the hub + during system suspend. This may reduce power consumption while + the system is suspended. + + To compile this driver as a module, choose M here: the + module will be called onboard_usb_hub. diff --git a/drivers/usb/misc/Makefile b/drivers/usb/misc/Makefile index da39bddb0604..6f10a1c6f7e9 100644 --- a/drivers/usb/misc/Makefile +++ b/drivers/usb/misc/Makefile @@ -31,3 +31,4 @@ obj-$(CONFIG_USB_CHAOSKEY) += chaoskey.o obj-$(CONFIG_USB_SISUSBVGA) += sisusbvga/ obj-$(CONFIG_USB_LINK_LAYER_TEST) += lvstest.o +obj-$(CONFIG_USB_ONBOARD_HUB) += onboard_usb_hub.o diff --git a/drivers/usb/misc/onboard_usb_hub.c b/drivers/usb/misc/onboard_usb_hub.c new file mode 100644 index 000000000000..390ae9fe13d0 --- /dev/null +++ b/drivers/usb/misc/onboard_usb_hub.c @@ -0,0 +1,370 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Driver for onboard USB hubs + * + * Copyright (c) 2020, Google LLC + */ + +#include <linux/device.h> +#include <linux/init.h> +#include <linux/kernel.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/suspend.h> +#include <linux/usb.h> +#include <linux/usb/hcd.h> + +/************************** Platform driver **************************/ + +struct udev_node { + struct usb_device *udev; + struct list_head list; +}; + +struct onboard_hub { + struct regulator *vdd; + struct device *dev; + bool power_off_in_suspend; + bool is_powered_on; + bool going_away; + struct list_head udev_list; + 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 enable 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 udev_node *node; + bool power_off; + int rc = 0; + + if (!hub->power_off_in_suspend) + return 0; + + power_off = true; + + 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) + rc = onboard_hub_power_off(hub); + + return rc; +} + +static int __maybe_unused onboard_hub_resume(struct device *dev) +{ + struct onboard_hub *hub = dev_get_drvdata(dev); + int rc = 0; + + if (!hub->is_powered_on) + rc = onboard_hub_power_on(hub); + + return rc; +} + +static int onboard_hub_add_usbdev(struct onboard_hub *hub, struct usb_device *udev) +{ + struct udev_node *node; + int ret = 0; + + mutex_lock(&hub->lock); + + if (hub->going_away) { + ret = -EINVAL; + goto unlock; + } + + node = devm_kzalloc(hub->dev, sizeof(*node), GFP_KERNEL); + if (!node) { + ret = -ENOMEM; + goto unlock; + } + + node->udev = udev; + + list_add(&node->list, &hub->udev_list); + +unlock: + mutex_unlock(&hub->lock); + + return ret; +} + +static void onboard_hub_remove_usbdev(struct onboard_hub *hub, struct usb_device *udev) +{ + struct udev_node *node; + + smp_rmb(); + if (hub->going_away) { + /* + * We are most likely being called as a result of unbinding a USB device from + * onboard_hub_remove(). This function also holds the lock and iterates over + * 'udev_list'. Skip deleting the node in this case to avoid a self deadlock, + * keeping the node in the list isn't a problem, since the device is about to go + * away. + */ + return; + } + + mutex_lock(&hub->lock); + + list_for_each_entry(node, &hub->udev_list, list) { + if (node->udev == udev) { + list_del(&node->list); + break; + } + } + + mutex_unlock(&hub->lock); +} + +static ssize_t power_off_in_suspend_show(struct device *dev, struct device_attribute *attr, + char *buf) +{ + struct onboard_hub *hub = dev_get_drvdata(dev); + + return sprintf(buf, "%d\n", hub->power_off_in_suspend); +} + +static ssize_t power_off_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->power_off_in_suspend = val; + + return count; +} +static DEVICE_ATTR_RW(power_off_in_suspend); + +static struct attribute *onboard_hub_sysfs_entries[] = { + &dev_attr_power_off_in_suspend.attr, + NULL, +}; + +static const struct attribute_group onboard_hub_sysfs_group = { + .attrs = onboard_hub_sysfs_entries, +}; + +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 = devm_device_add_group(dev, &onboard_hub_sysfs_group); + if (err) { + dev_err(dev, "failed to create sysfs entries: %d\n", err); + return err; + } + + return onboard_hub_power_on(hub); +} + +static int onboard_hub_remove(struct platform_device *pdev) +{ + struct onboard_hub *hub = dev_get_drvdata(&pdev->dev); + struct udev_node *node; + + hub->going_away = true; + + mutex_lock(&hub->lock); + + /* unbind the USB devices to avoid dangling references to this device */ + list_for_each_entry(node, &hub->udev_list, list) + device_release_driver(&node->udev->dev); + + mutex_unlock(&hub->lock); + + return onboard_hub_power_off(hub); +} + +static const struct of_device_id onboard_hub_match[] = { + { .compatible = "onboard-usb-hub" }, + { .compatible = "realtek,rts5411" }, + {} +}; +MODULE_DEVICE_TABLE(of, onboard_hub_match); + +static SIMPLE_DEV_PM_OPS(onboard_hub_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), + }, +}; + +/************************** USB driver **************************/ + +#define VENDOR_ID_REALTEK 0x0bda + +static struct onboard_hub *_find_onboard_hub(struct device *dev) +{ + const phandle *ph; + struct device_node *np; + struct platform_device *pdev; + + ph = of_get_property(dev->of_node, "hub", NULL); + if (!ph) { + dev_err(dev, "failed to read 'hub' property\n"); + return ERR_PTR(-EINVAL); + } + + np = of_find_node_by_phandle(be32_to_cpu(*ph)); + if (!np) { + dev_err(dev, "failed find device node for onboard hub\n"); + return ERR_PTR(-EINVAL); + } + + pdev = of_find_device_by_node(np); + of_node_put(np); + if (!pdev) + return ERR_PTR(-EPROBE_DEFER); + + put_device(&pdev->dev); + + return dev_get_drvdata(&pdev->dev); +} + +static int onboard_hub_usbdev_probe(struct usb_device *udev) +{ + struct device *dev = &udev->dev; + struct onboard_hub *hub; + + /* 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(dev); + + dev_set_drvdata(dev, hub); + + return onboard_hub_add_usbdev(hub, udev); +} + +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 3.0 */ + { USB_DEVICE(VENDOR_ID_REALTEK, 0x5411) }, /* RTS5411 USB 2.0 */ + {}, +}; + +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, +}; + +/************************** Driver (de)registration **************************/ + +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");