Date:   Thu, 7 Apr 2022 12:41:22 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Felipe Balbi <balbi@...nel.org>,
        Linux USB List <linux-usb@...r.kernel.org>,
        Ravi Chandra Sadineni <ravisadineni@...omium.org>,
        Roger Quadros <rogerq@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Bastien Nocera <hadess@...ess.net>,
        Michal Simek <michal.simek@...inx.com>,
        Stephen Boyd <swboyd@...omium.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Peter Chen <peter.chen@...nel.org>,
        Guo Zhengkui <guozhengkui@...o.com>,
        Kishon Vijay Abraham I <kishon@...com>,
        Li Jun <jun.li@....com>, Peter Chen <peter.chen@....com>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>
Subject: Re: [PATCH v21 0/3] usb: misc: Add onboard_usb_hub driver

Hi,

On Thu, Feb 17, 2022 at 10:43 AM Matthias Kaehlcke <mka@...omium.org> wrote:
>
> This series adds:
> - the onboard_usb_hub_driver
> - glue in the generic HCD code to create and destroy the
>   onboard_usb_hub platform devices if needed
> - device tree changes that add RTS5411 entries for the QCA SC7180
>   based boards trogdor and lazor
> - a couple of stubs for platform device functions to avoid
>   unresolved symbols with certain kernel configs
>
> The main issue the 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.
>
> Changes in v21:
> - dropped patch 'driver core: Export device_is_bound()'
> - refactored _find_onboard_hub()
> - removed 'onboard_hub_dev' symlinks from USB devices
> - dropped patch 'arm64: dts: qcom: sc7180-trogdor: Add nodes for onboard USB hub'
>   (will be sent separately)
> - rebased series on v5.17-rc4
>
> Changes in v20:
> - addressed review comments from Stephen
> - changed DT node names for hubs
>
> Changes in v19:
> - added VID:PID pairs and compatible strings for RTS5414 hub
> - updated comments with RTS5411 USB versions to reflect those
>   reported/supported by the hub
> - rebased series on v5.16
>
> Changes in v18:
> - introduced hidden Kconfig option to align module vs. builtin
>   choice with CONFIG_USB (thanks Doug!)
> - added patch 'driver core: Export device_is_bound()'
> - also adjust device tree of pompom rev1
> - dropped the following patches, which aren't needed anymore by this
>   series (though they might still be useful on their own):
>   - usb: Specify dependencies on USB_XHCI_PLATFORM with 'depends on'
>   - arm64: defconfig: Explicitly enable USB_XHCI_PLATFORM
>   - ARM: configs: Explicitly enable USB_XHCI_PLATFORM where needed
>
> Changes in v17:
> - rebased on top of v5.16-rc1
> - moved creation of onboard_hub platform devices from xhci_platform
>   to the generic HCD code
> - addressed review comments for the onboard_hub driver
> - moved Kconfig/defconfig changes to the end of the series. The
>   onboard_hub driver doesn't depend on XHCI_PLATFORM anymore,
>   hence these changes aren't really required for the driver, but
>   they still seem to be a worthwhile improvement
>
> Changes in v16:
> - added patch 'ARM: configs: Explicitly enable USB_XHCI_PLATFORM
>   where needed' to keep arm32 defconfigs effectively unchanged
>
> Changes in v15:
> - adjusted dependencies of USB_DWC3_CORE to make sure it can only
>   be enabled when at least one of USB_DWC3_HOST, USB_DWC3_GADGET
>   or USB_DWC3_DUAL_ROLE is selectable
>
> Changes in v14:
> - rebased on top of v5.14-rc1
> - dropped DT binding patch which landed in v5.13
>
> Changes in v13:
> - added patch "usb: Specify dependency on USB_XHCI_PLATFORM with
>   'depends on'" to the series to avoid Kconfig conflicts
> - added patch "arm64: defconfig: Explicitly enable USB_XHCI_PLATFORM"
>   to the series to keep effective defconfig unchanged
>
> Changes in v12:
> - onboard_hub driver: use IS_ENABLED(CONFIG_USB_ONBOARD_HUB_MODULE)
>   in onboard_hub.h to also check for the driver built as module
> - onboard_hub_driver: include onboard_hub.h again to make sure there
>   are prototype declarations for the public functions
>
> Changes in v11:
> - support multiple onboard hubs connected to the same parent
> - don't include ‘onboard_hub.h’ from the onboard hub driver
>
> Changes in v10:
> - always use of_is_onboard_usb_hub() stub unless ONBOARD_USB_HUB=y/m
> - keep 'regulator-boot-on' property for pp3300_hub
>
> Changes in v9:
> - added dependency on ONBOARD_USB_HUB (or !ONBOARD_USB_HUB) to
>   USB_PLATFORM_XHCI
>
> Changes in v7:
> - updated DT binding
> - series rebased on qcom/arm64-for-5.13
>
> Changes in v6:
> - updated summary
>
> Changes in v5:
> - cover letter added
>
> Matthias Kaehlcke (3):
>   of/platform: Add stubs for of_platform_device_create/destroy()
>   usb: misc: Add onboard_usb_hub driver
>   usb: core: hcd: Create platform devices for onboard hubs in probe()
>
>  .../sysfs-bus-platform-onboard-usb-hub        |   8 +
>  MAINTAINERS                                   |   7 +
>  drivers/usb/core/hcd.c                        |   6 +
>  drivers/usb/misc/Kconfig                      |  23 +
>  drivers/usb/misc/Makefile                     |   1 +
>  drivers/usb/misc/onboard_usb_hub.c            | 510 ++++++++++++++++++
>  include/linux/of_platform.h                   |  22 +-
>  include/linux/usb/hcd.h                       |   1 +
>  include/linux/usb/onboard_hub.h               |  18 +
>  9 files changed, 592 insertions(+), 4 deletions(-)
>  create mode 100644 Documentation/ABI/testing/sysfs-bus-platform-onboard-usb-hub
>  create mode 100644 drivers/usb/misc/onboard_usb_hub.c
>  create mode 100644 include/linux/usb/onboard_hub.h

With v5.18-rc1 out the door, I wonder if it's a good time to look at
this series again. Are there any hidden blockers that it's waiting
for?

-Doug

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