Date:   Tue, 1 Sep 2020 14:21:49 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ravi Chandra Sadineni <ravisadineni@...omium.org>,
        Bastien Nocera <hadess@...ess.net>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Stephen Boyd <swboyd@...omium.org>, linux-usb@...r.kernel.org,
        Alan Stern <stern@...land.harvard.edu>,
        "Alexander A. Klimov" <grandmaster@...klimov.de>,
        Masahiro Yamada <masahiroy@...nel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, Rob Herring <robh+dt@...nel.org>
Subject: Re: [RFC PATCH] USB: misc: Add usb_hub_pwr driver

Hi,

On Tue, Sep 1, 2020 at 1:21 PM Matthias Kaehlcke <mka@...omium.org> wrote:
>
> The driver combo usb_hub_pwr/usb_hub_psupply allows to control
> the power supply of an onboard USB hub.
>
> The drivers address two issues:
>  - a USB hub needs to be powered before it can be discovered
>  - battery powered devices may want to switch the USB hub off
>    during suspend to extend battery life
>
> The regulator of the hub is controlled by the usb_hub_psupply
> platform driver. The regulator is switched on when the platform
> device is initialized, which enables discovery of the hub. The
> driver provides an external interface to enable/disable the
> power supply which is used by the usb_hub_pwr driver.
>
> The usb_hub_pwr extends the generic USB hub driver. The device is
> initialized when the hub is discovered by the USB subsystem. It
> uses the usb_hub_psupply interface to make its own request to
> enable the regulator (increasing the use count to 2).
>
> During system suspend usb_hub_pwr checks if any wakeup capable
> devices are connected to the hub. If not it 'disables' the hub
> regulator (decreasing the use count to 1, hence the regulator
> stays enabled for now). When the usb_hub_psupply device suspends
> it disables the hub regulator unconditionally (decreasing the use
> count to 0 or 1, depending on the actions of usb_hub_pwr). This
> is done to allow the usb_hub_pwr device to control the state of
> the regulator during system suspend.
>
> Upon resume usb_hub_psupply enables the regulator again, the
> usb_hub_pwr device does the same if it disabled the regulator
> during resume.
>
> 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>
> ---
> The driver currently only supports a single power supply. This should
> work for most/many configurations/hubs, support for multiple power
> supplies can be added later if needed.
>
> No DT bindings are included since this is just a RFC. Here is a DT
> example:
>
> usb_hub_psupply: usb-hub-psupply {
>     compatible = "linux,usb_hub_psupply";
>     vdd-supply = <&pp3300_hub>;
> };

Definitely bikeshedding, but I would name this differently.  The
name/compatible you have makes this sound as if it's a software
concept that we're sticking into DT.  That's generally discouraged.
...if we name it slightly different then I think the driver can work
the same but be more in the spirit of DT describing hardware.
Specifically, I think it'd be better as:

usb_hub: usb-hub {
  compatible = "realtek,rts5411", "onboard-usb-hub";
  vdd-supply = <&pp3300_hub>;
};

Now we're describing hardware that's on the board.  We have a RTS5411
hub and we've described its power supply.  There's also precedent for
describing an on-board USB hub in a lop-level node like this
(smsc,usb3503).

Now, I know what you're saying: we're already describing this hub
underneath the USB port node below.  I think this is OK to have
different aspects of the device described in two places in the DT,
though of course I could be corrected by someone more knowledgeable.


> &usb_1_dwc3 {
>     /* 2.0 hub on port 1 */
>     hub@1 {
>         compatible = "usbbda,5411";

What is "usbbda"?  I would probably just call this:

compatible = "realtek,rts5411-usb2", "onboard-usb-hub-usb2"


>         reg = <1>;
>         psupply = <&usb_hub_psupply>;

Calling this psupply sounds a bit too much like you're referring to a
regulator (with the -supply suffix).  Given that I've proposed calling
the main device "usb-hub" what about just saying "hub = <&usb_hub>;"


>     };
>
>     /* 3.0 hub on port 2 */
>     hub@2 {
>         compatible = "usbbda,411";

Similar to above:

compatible = "realtek,rts5411-usb3", "onboard-usb-hub-usb3"


>         reg = <2>;
>         psupply = <&usb_hub_psupply>;
>     };
> };
>
>  drivers/usb/misc/Kconfig           |  14 +++
>  drivers/usb/misc/Makefile          |   1 +
>  drivers/usb/misc/usb_hub_psupply.c | 112 ++++++++++++++++++
>  drivers/usb/misc/usb_hub_psupply.h |   9 ++
>  drivers/usb/misc/usb_hub_pwr.c     | 177 +++++++++++++++++++++++++++++
>  5 files changed, 313 insertions(+)
>  create mode 100644 drivers/usb/misc/usb_hub_psupply.c
>  create mode 100644 drivers/usb/misc/usb_hub_psupply.h
>  create mode 100644 drivers/usb/misc/usb_hub_pwr.c
>
> diff --git a/drivers/usb/misc/Kconfig b/drivers/usb/misc/Kconfig
> index 6818ea689cd9..79ed50e6a7bf 100644
> --- a/drivers/usb/misc/Kconfig
> +++ b/drivers/usb/misc/Kconfig
> @@ -275,3 +275,17 @@ config USB_CHAOSKEY
>
>           To compile this driver as a module, choose M here: the
>           module will be called chaoskey.
> +
> +config USB_HUB_PWR
> +       tristate "Control power supply for onboard USB hubs"
> +       depends on PM
> +       help
> +         Say Y here if you want to control the power supply of an
> +         onboard USB hub. The driver switches the power supply of the
> +         hub on, to make sure the hub can be discovered. During system
> +         suspend the power supply is switched off, unless a wakeup
> +         capable device is connected to the hub. This may reduce power
> +         consumption on battery powered devices.
> +
> +         To compile this driver as a module, choose M here: the
> +         module will be called usb_hub_pwr.
> diff --git a/drivers/usb/misc/Makefile b/drivers/usb/misc/Makefile
> index da39bddb0604..2bd02388ca62 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_HUB_PWR)              += usb_hub_pwr.o usb_hub_psupply.o
> diff --git a/drivers/usb/misc/usb_hub_psupply.c b/drivers/usb/misc/usb_hub_psupply.c
> new file mode 100644
> index 000000000000..6a155ae1f831
> --- /dev/null
> +++ b/drivers/usb/misc/usb_hub_psupply.c
> @@ -0,0 +1,112 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (c) 2020, Google LLC
> + */
> +
> +#include <linux/init.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/regulator/consumer.h>
> +
> +struct usb_hub_psupply_dev {
> +       struct regulator *vdd;
> +};

Until someone has a need for more, I'd just pass your "struct
regulator *" as the driver data and get rid of this pointless wrapper.


> +int usb_hub_psupply_on(struct device *dev)
> +{
> +       struct usb_hub_psupply_dev *usb_hub_psupply = dev_get_drvdata(dev);
> +       int err;
> +
> +       err = regulator_enable(usb_hub_psupply->vdd);
> +       if (err) {
> +               dev_err(dev, "failed to enable regulator: %d\n", err);
> +               return err;
> +       }
> +
> +       return 0;
> +

nit: blank line


> +}
> +EXPORT_SYMBOL_GPL(usb_hub_psupply_on);
> +
> +int usb_hub_psupply_off(struct device *dev)
> +{
> +       struct usb_hub_psupply_dev *usb_hub_psupply = dev_get_drvdata(dev);
> +       int err;
> +
> +       err = regulator_disable(usb_hub_psupply->vdd);
> +       if (err) {
> +               dev_err(dev, "failed to enable regulator: %d\n", err);
> +               return err;
> +       }
> +
> +       return 0;
> +}
> +EXPORT_SYMBOL_GPL(usb_hub_psupply_off);
> +
> +static int usb_hub_psupply_probe(struct platform_device *pdev)
> +{
> +       struct device *dev = &pdev->dev;
> +       struct usb_hub_psupply_dev *usb_hub_psupply;
> +
> +       usb_hub_psupply = devm_kzalloc(dev, sizeof(*usb_hub_psupply), GFP_KERNEL);
> +       if (!usb_hub_psupply)
> +               return -ENOMEM;
> +
> +       dev_set_drvdata(dev, usb_hub_psupply);
> +
> +       usb_hub_psupply->vdd = devm_regulator_get(dev, "vdd");
> +       if (IS_ERR(usb_hub_psupply->vdd))
> +               return PTR_ERR(usb_hub_psupply->vdd);
> +
> +       return usb_hub_psupply_on(dev);
> +}
> +
> +static int usb_hub_psupply_remove(struct platform_device *pdev)
> +{
> +       return usb_hub_psupply_off(&pdev->dev);
> +}
> +
> +static int usb_hub_psupply_suspend(struct platform_device *pdev, pm_message_t msg)
> +{
> +       return usb_hub_psupply_off(&pdev->dev);
> +}
> +
> +static int usb_hub_psupply_resume(struct platform_device *pdev)
> +{
> +       return usb_hub_psupply_on(&pdev->dev);
> +}
> +
> +static const struct of_device_id usb_hub_psupply_match[] = {
> +       { .compatible = "linux,usb_hub_psupply" },
> +       {}
> +};
> +MODULE_DEVICE_TABLE(of, usb_hub_psupply_match);
> +
> +static struct platform_driver usb_hub_psupply_driver = {
> +       .probe = usb_hub_psupply_probe,
> +       .remove = usb_hub_psupply_remove,
> +       .suspend = usb_hub_psupply_suspend,

SET_SYSTEM_SLEEP_PM_OPS?  Then you also need to add "__maybe_unused"
to your suspend/resume functions.


> +       .resume = usb_hub_psupply_resume,
> +       .driver = {
> +               .name = "usb-hub-psupply",
> +               .of_match_table = usb_hub_psupply_match,
> +       },
> +};
> +
> +static int __init usb_hub_psupply_init(void)
> +{
> +       return platform_driver_register(&usb_hub_psupply_driver);
> +}
> +device_initcall(usb_hub_psupply_init);
> +
> +static void __exit usb_hub_psupply_exit(void)
> +{
> +       platform_driver_unregister(&usb_hub_psupply_driver);
> +}
> +module_exit(usb_hub_psupply_exit);
> +
> +MODULE_AUTHOR("Matthias Kaehlcke <mka@...omium.org>");
> +MODULE_DESCRIPTION("USB Hub Power Supply");
> +MODULE_LICENSE("GPL v2");
> diff --git a/drivers/usb/misc/usb_hub_psupply.h b/drivers/usb/misc/usb_hub_psupply.h
> new file mode 100644
> index 000000000000..284e88f45fcf
> --- /dev/null
> +++ b/drivers/usb/misc/usb_hub_psupply.h
> @@ -0,0 +1,9 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +
> +#ifndef _USB_HUB_PSUPPLY_H
> +#define _USB_HUB_PSUPPLY_H
> +
> +int usb_hub_psupply_on(struct device *dev);
> +int usb_hub_psupply_off(struct device *dev);
> +
> +#endif /* _USB_HUB_PSUPPLY_H */
> diff --git a/drivers/usb/misc/usb_hub_pwr.c b/drivers/usb/misc/usb_hub_pwr.c
> new file mode 100644
> index 000000000000..33945ca4a8c0
> --- /dev/null
> +++ b/drivers/usb/misc/usb_hub_pwr.c
> @@ -0,0 +1,177 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * USB hub power control
> + *
> + * Copyright (c) 2020, Google LLC
> + */
> +
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_platform.h>
> +#include <linux/power_supply.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/slab.h>
> +#include <linux/usb.h>
> +#include <linux/usb/hcd.h>
> +#include "../core/usb.h"
> +#include "usb_hub_psupply.h"
> +
> +#define VENDOR_ID_REALTEK      0x0bda
> +
> +struct usb_hub_pwr_dev {
> +       struct regulator *vdd;

You don't use the regulator directly, right?  So get rid of "vdd" here?


> +       struct device *psupply_dev;
> +       bool powered_off;
> +};
> +
> +static struct device *usb_pwr_find_psupply_dev(struct device *dev)
> +{
> +       const phandle *ph;
> +       struct device_node *np;
> +       struct platform_device *pdev;
> +
> +       ph = of_get_property(dev->of_node, "psupply", NULL);
> +       if (!ph) {
> +               dev_err(dev, "failed to read 'psupply' 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 power supply\n");
> +               return ERR_PTR(-EINVAL);
> +       }
> +
> +       pdev = of_find_device_by_node(np);
> +       of_node_put(np);
> +       if (!pdev)
> +               return ERR_PTR(-EPROBE_DEFER);
> +
> +       return &pdev->dev;
> +}
> +
> +static int usb_hub_pwr_probe(struct usb_device *udev)
> +{
> +       struct device *dev = &udev->dev;
> +       struct usb_hub_pwr_dev *uhpw;
> +       struct device *psupply_dev;
> +       int err;
> +
> +       /* ignore supported hubs without device tree node */
> +       if (!dev->of_node)
> +               return -ENODEV;

I can dig through the code if you don't know, but I'm hoping that
-ENODEV means it'll fall back to the regular hub driver?


> +       psupply_dev = usb_pwr_find_psupply_dev(dev);
> +       if (IS_ERR(psupply_dev))
> +               return PTR_ERR(psupply_dev);
> +
> +       err = usb_generic_driver_probe(udev);
> +       if (err) {
> +               put_device(psupply_dev);
> +               return err;
> +       }
> +
> +       uhpw = devm_kzalloc(dev, sizeof(*uhpw), GFP_KERNEL);
> +       if (!uhpw) {
> +               put_device(psupply_dev);
> +               return -ENOMEM;
> +       }
> +
> +       dev_set_drvdata(&udev->dev, uhpw);
> +
> +       uhpw->psupply_dev = psupply_dev;
> +
> +       err = usb_hub_psupply_on(psupply_dev);
> +       if (err) {
> +               dev_err(dev, "failed to enable regulator: %d\n", err);
> +               put_device(psupply_dev);
> +               return err;
> +       }
> +
> +       return 0;
> +}
> +
> +static void usb_hub_pwr_disconnect(struct usb_device *udev)
> +{
> +       struct usb_hub_pwr_dev *uhpw = dev_get_drvdata(&udev->dev);
> +
> +       usb_hub_psupply_off(uhpw->psupply_dev);
> +       put_device(uhpw->psupply_dev);
> +}
> +
> +static int usb_hub_pwr_suspend(struct usb_device *udev, pm_message_t msg)
> +{
> +       struct usb_hub_pwr_dev *uhpw = dev_get_drvdata(&udev->dev);
> +       int err;
> +
> +       err = usb_generic_driver_suspend(udev, msg);
> +       if (err)
> +               return err;
> +
> +       if (!usb_wakeup_enabled_descendants(udev)) {
> +               usb_port_disable(udev);
> +
> +               err = usb_hub_psupply_off(uhpw->psupply_dev);
> +               if (err)
> +                       return err;
> +
> +               uhpw->powered_off = true;
> +       }
> +
> +       return 0;
> +}
> +
> +static int usb_hub_pwr_resume(struct usb_device *udev, pm_message_t msg)
> +{
> +       struct usb_hub_pwr_dev *uhpw = dev_get_drvdata(&udev->dev);
> +       int err;
> +
> +       if (uhpw->powered_off) {
> +               err = usb_hub_psupply_on(uhpw->psupply_dev);
> +               if (err)
> +                       return err;
> +
> +               uhpw->powered_off = false;
> +       }
> +
> +       return usb_generic_driver_resume(udev, msg);
> +}
> +
> +static const struct usb_device_id 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, hub_id_table);
> +
> +static struct usb_device_driver usb_hub_pwr_driver = {
> +
> +       .name = "usb-hub-pwr",
> +       .probe = usb_hub_pwr_probe,
> +       .disconnect = usb_hub_pwr_disconnect,
> +       .suspend = usb_hub_pwr_suspend,
> +       .resume = usb_hub_pwr_resume,
> +       .id_table = hub_id_table,

I'm not an expert, but do you need "supports_autosuspend"?  I think we
want autosuspend enabled so nothing is plugged into the hub (or only
things that can autosuspend) then we can save power.  I can dig more
too, if you don't know.


> +};
> +
> +static int __init usb_hub_pwr_driver_init(void)
> +{
> +       return usb_register_device_driver(&usb_hub_pwr_driver, THIS_MODULE);
> +}
> +
> +static void __exit usb_hub_pwr_driver_exit(void)
> +{
> +       usb_deregister_device_driver(&usb_hub_pwr_driver);
> +}
> +
> +module_init(usb_hub_pwr_driver_init);
> +module_exit(usb_hub_pwr_driver_exit);
> +
> +MODULE_AUTHOR("Matthias Kaehlcke <mka@...omium.org>");
> +MODULE_DESCRIPTION("USB Hub Power Control");
> +MODULE_LICENSE("GPL v2");

All the above is mostly just nits.  To me the concept here seems sane.

-Doug

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