Message-ID: <20200918012935.GA3938@b29397-desktop>
Date:   Fri, 18 Sep 2020 01:30:20 +0000
From:   Peter Chen <peter.chen@....com>
To:     Matthias Kaehlcke <mka@...omium.org>
CC:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Douglas Anderson <dianders@...omium.org>,
        Alan Stern <stern@...land.harvard.edu>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        Bastien Nocera <hadess@...ess.net>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Ravi Chandra Sadineni <ravisadineni@...omium.org>,
        Stephen Boyd <swboyd@...omium.org>,
        "Alexander A. Klimov" <grandmaster@...klimov.de>,
        Masahiro Yamada <masahiroy@...nel.org>
Subject: Re: [PATCH v2 2/2] USB: misc: Add onboard_usb_hub driver

On 20-09-17 11:46:22, 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@...omium.org>
> Signed-off-by: Ravi Chandra Sadineni <ravisadineni@...omium.org>
> Signed-off-by: Matthias Kaehlcke <mka@...omium.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"

On board HUB belongs to HUB, this driver is just for possible power and
initialization requirements for HUB which is hard-wired on board. The
configuration name USB_HUB_POWER_SUPPLY may more suitable, and at the
menu and help, you could indicate it is special for HUBs which are
hard-wired on board.

> +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);
> +	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);
> +	if (rc)
> +		return rc;

You could use dev_groups for sysfs entry management.

> +/************************** 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);
> +
> +	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 },
> +	{},
> +};
> +
> +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);
> +}
> +device_initcall(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@...omium.org>");
> +MODULE_DESCRIPTION("Onboard USB Hub driver");

Improve the description like mentioned above.

-- 

Thanks,
Peter Chen

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