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SubjectRe: [PATCH v2 2/2] USB: misc: Add onboard_usb_hub driver
On Thu, Sep 17, 2020 at 11:46:22AM -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 onboard hubs 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 further 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>
> ---
>
> Changes in v2:
> - check wakeup enabled state of the USB controller instead of
> using 'wakeup-source' property
> - use sysfs attribute instead of DT property to determine if
> the hub should be powered off at all during system suspend
> - added missing brace in onboard_hub_suspend()
> - updated commit message
> - use pm_ptr for pm_ops as suggested by Alan
>
> Changes in v1:
> - renamed the driver to 'onboard_usb_hub'
> - single file for platform and USB driver
> - USB hub devices register with the platform device
> - the DT includes a phandle of the platform device
> - the platform device now controls when power is turned off
> - the USB driver became a very thin subclass of the generic USB
> driver
> - enabled autosuspend support
>
> drivers/usb/misc/Kconfig | 15 ++
> drivers/usb/misc/Makefile | 1 +
> drivers/usb/misc/onboard_usb_hub.c | 329 +++++++++++++++++++++++++++++
> 3 files changed, 345 insertions(+)
> create mode 100644 drivers/usb/misc/onboard_usb_hub.c
>
> diff --git a/drivers/usb/misc/Kconfig b/drivers/usb/misc/Kconfig
> index 6818ea689cd9..e941244e24e5 100644
> --- a/drivers/usb/misc/Kconfig
> +++ b/drivers/usb/misc/Kconfig
> @@ -275,3 +275,18 @@ 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

What about COMPILE_TEST as well?

> + help
> + Say Y here if you want to support onboard USB hubs. The driver
> + powers supported hubs on and may perform other initialization
> + steps.
> +
> + The driver can also switch off the power of the hub during
> + system suspend if it is configured accordingly. 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..206798029041
> --- /dev/null
> +++ b/drivers/usb/misc/onboard_usb_hub.c
> @@ -0,0 +1,329 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Driver for onboard USB hubs
> + *
> + * Copyright (c) 2020, Google LLC
> + */
> +
> +#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>
> +#include "../core/usb.h"

Why do you need private usb core functions?

> +
> +/************************** 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;
> + struct list_head udev_list;
> + struct mutex lock;
> + bool has_wakeup_capable_descendants;
> +};
> +
> +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;
> + }

Nit, no need for { } or return err here, just return err one line below.

> +
> + 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;
> + }
> +
> + return 0;

Same here.

> +}
> +
> +static int __maybe_unused onboard_hub_suspend(struct device *dev)
> +{
> + struct onboard_hub *hub = dev_get_drvdata(dev);
> + struct udev_node *node;
> + int rc = 0;
> +
> + hub->has_wakeup_capable_descendants = false;
> +
> + if (!hub->power_off_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))
> + break;
> +
> + if (usb_wakeup_enabled_descendants(node->udev)) {
> + hub->has_wakeup_capable_descendants = true;
> + break;
> + }
> + }
> +
> + mutex_unlock(&hub->lock);
> +
> + if (!hub->has_wakeup_capable_descendants)
> + 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->power_off_in_suspend && !hub->has_wakeup_capable_descendants)
> + 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;
> +
> + node = devm_kzalloc(hub->dev, sizeof(*node), GFP_KERNEL);
> + if (!node)
> + return -ENOMEM;
> +
> + node->udev = udev;

No reference counting? Are you sure about this?

> +
> + mutex_lock(&hub->lock);
> + list_add(&node->list, &hub->udev_list);
> + mutex_unlock(&hub->lock);
> +
> + return 0;
> +}
> +
> +static int onboard_hub_remove_usbdev(struct onboard_hub *hub, struct usb_device *udev)
> +{
> + struct udev_node *node;
> +
> + mutex_lock(&hub->lock);
> +
> + list_for_each_entry(node, &hub->udev_list, list) {

list_for_each_entry_safe()?

> + if (node->udev == udev) {
> + list_del(&node->list);
> + devm_kfree(hub->dev, node);
> + break;
> + }
> + }
> +
> + mutex_unlock(&hub->lock);
> +
> + if (node == NULL)
> + return -EINVAL;
> +
> + return 0;
> +}
> +
> +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 = strtobool(buf, &val);

You should use kstrtobool() instead, right?

> + if (ret < 0)
> + return ret;
> +
> + hub->power_off_in_suspend = val;
> +
> + return count;
> +}
> +static DEVICE_ATTR_RW(power_off_in_suspend);
> +
> +static int onboard_hub_probe(struct platform_device *pdev)
> +{
> + struct device *dev = &pdev->dev;
> + struct onboard_hub *hub;
> + int rc;
> +
> + 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);
> +
> + rc = sysfs_create_file(&dev->kobj, &dev_attr_power_off_in_suspend.attr);

Use the default platform device files group, never create/add your own
sysfs files "by hand", otherwise it could go easily wrong.


> + if (rc)
> + return rc;
> +
> + return onboard_hub_power_on(hub);
> +}
> +
> +static int onboard_hub_remove(struct platform_device *pdev)
> +{
> + struct onboard_hub *hub = dev_get_drvdata(&pdev->dev);
> +
> + sysfs_remove_file(&pdev->dev.kobj, &dev_attr_power_off_in_suspend.attr);

If you do the above, no need to remove this here.

> +
> + 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);

Why can you defer here?

> +
> + 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);
> +
> + onboard_hub_add_usbdev(hub, udev);
> +
> + 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);
> +
> + put_device(hub->dev);
> +}
> +
> +static const struct usb_device_id onboard_hub_id_table[] = {
> + { .idVendor = VENDOR_ID_REALTEK,
> + .idProduct = 0x0411, /* RTS5411 USB 3.0 */
> + .match_flags = USB_DEVICE_ID_MATCH_DEVICE },
> + { .idVendor = VENDOR_ID_REALTEK,
> + .idProduct = 0x5411, /* RTS5411 USB 2.0 */
> + .match_flags = USB_DEVICE_ID_MATCH_DEVICE },

USB_DEVICE() should be used here instead for both of these, right?

> + {},
> +};
> +
> +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 rc;
> +
> + rc = platform_driver_register(&onboard_hub_driver);
> + if (rc)
> + return rc;
> +
> + return usb_register_device_driver(&onboard_hub_usbdev_driver, THIS_MODULE);

No unwinding of the platform driver register if this fails?

And THIS_MODULE should not be needed, did we get the api wrong here?

> +}
> +device_initcall(onboard_hub_init);

Why device_initcall() if this could be a module? Why not a normal
module_init()?

thanks,

greg k-h

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