From: Alan Stern <stern@rowland.harvard.edu>
To: Matthias Kaehlcke <mka@chromium.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Rob Herring <robh+dt@kernel.org>,
Frank Rowand <frowand.list@gmail.com>,
Krzysztof Kozlowski <krzk@kernel.org>,
Bastien Nocera <hadess@hadess.net>,
Ravi Chandra Sadineni <ravisadineni@chromium.org>,
linux-usb@vger.kernel.org, Stephen Boyd <swboyd@chromium.org>,
devicetree@vger.kernel.org,
Douglas Anderson <dianders@chromium.org>,
Peter Chen <peter.chen@nxp.com>,
linux-kernel@vger.kernel.org,
"Alexander A. Klimov" <grandmaster@al2klimov.de>,
Masahiro Yamada <masahiroy@kernel.org>
Subject: Re: [PATCH 2/2] USB: misc: Add onboard_usb_hub driver
Date: Mon, 14 Sep 2020 16:14:03 -0400 [thread overview]
Message-ID: <20200914201403.GA977844@rowland.harvard.edu> (raw)
In-Reply-To: <20200914112716.2.I7c9a1f1d6ced41dd8310e8a03da666a32364e790@changeid>
On Mon, Sep 14, 2020 at 11:27:49AM -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 keeping it powered otherwise.
>
> Technically the driver consists of two drivers, the platform driver
> described above and a very thin USB driver that subclasses the
> generic hub driver.
Actually it subclasses the generic usb device driver, not the hub
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>
> ---
> This is an evolution of '[RFC] USB: misc: Add usb_hub_pwr driver'
> (https://lore.kernel.org/patchwork/patch/1299239/).
>
> 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 hub
> driver
> - enabled autosuspend support
See https://marc.info/?l=linux-usb&m=159914635920888&w=2 and the
accompanying submissions. You'll probably want to include those updates
in your driver.
Alan Stern
next prev parent reply other threads:[~2020-09-14 20:14 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-14 18:27 [PATCH 1/2] dt-bindings: usb: Add binding for onboard USB hubs Matthias Kaehlcke
2020-09-14 18:27 ` [PATCH 2/2] USB: misc: Add onboard_usb_hub driver Matthias Kaehlcke
2020-09-14 19:52 ` Matthias Kaehlcke
2020-09-14 20:14 ` Alan Stern [this message]
2020-09-14 21:14 ` Matthias Kaehlcke
2020-09-15 2:55 ` Peter Chen
2020-09-15 5:02 ` Matthias Kaehlcke
2020-09-15 7:05 ` Peter Chen
2020-09-15 23:03 ` Matthias Kaehlcke
2020-09-16 2:14 ` Alan Stern
2020-09-16 19:27 ` Matthias Kaehlcke
2020-09-16 8:19 ` Peter Chen
2020-09-16 19:16 ` Matthias Kaehlcke
2020-09-17 0:27 ` Peter Chen
2020-09-17 0:47 ` Matthias Kaehlcke
2020-09-17 1:24 ` Peter Chen
2020-09-17 15:54 ` Matthias Kaehlcke
2020-09-15 14:21 ` [PATCH 1/2] dt-bindings: usb: Add binding for onboard USB hubs Rob Herring
2020-09-16 0:00 ` Matthias Kaehlcke
2020-09-18 16:05 ` Rob Herring
2020-09-22 23:39 ` Matthias Kaehlcke
2020-09-15 14:21 ` Rob Herring
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