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From: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
To: Matthias Kaehlcke <mka@chromium.org>
Cc: "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	"Alan Stern" <stern@rowland.harvard.edu>,
	"Rob Herring" <robh+dt@kernel.org>,
	"Frank Rowand" <frowand.list@gmail.com>,
	"Mathias Nyman" <mathias.nyman@intel.com>,
	"Felipe Balbi" <balbi@kernel.org>,
	"Bastien Nocera" <hadess@hadess.net>,
	"Peter Chen" <peter.chen@kernel.org>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
	<devicetree@vger.kernel.org>,
	"Michal Simek" <michal.simek@xilinx.com>,
	"open list" <linux-kernel@vger.kernel.org>,
	"Douglas Anderson" <dianders@chromium.org>,
	"Krzysztof Kozlowski" <krzk@kernel.org>,
	linux-usb@vger.kernel.org,
	"Ravi Chandra Sadineni" <ravisadineni@chromium.org>,
	"Stephen Boyd" <swboyd@chromium.org>,
	"Al Cooper" <alcooperx@gmail.com>,
	"Andrey Zhizhikin" <andrey.zhizhikin@leica-geosystems.com>,
	"Andy Gross" <agross@kernel.org>,
	"Aswath Govindraju" <a-govindraju@ti.com>,
	"Bjorn Andersson" <bjorn.andersson@linaro.org>,
	"Catalin Marinas" <catalin.marinas@arm.com>,
	"Dmitry Osipenko" <digetx@gmail.com>,
	"Enric Balletbo i Serra" <enric.balletbo@collabora.com>,
	"Fabio Estevam" <festevam@gmail.com>,
	"Guido Günther" <agx@sigxcpu.org>,
	"Jagan Teki" <jagan@amarulasolutions.com>,
	"Nishanth Menon" <nm@ti.com>,
	"Pawel Laszczak" <pawell@cadence.com>,
	"Roger Quadros" <rogerq@kernel.org>,
	"Shawn Guo" <shawnguo@kernel.org>,
	"Vinod Koul" <vkoul@kernel.org>, "Will Deacon" <will@kernel.org>,
	"Linux ARM" <linux-arm-kernel@lists.infradead.org>,
	"open list:DRM DRIVER FOR MSM ADRENO GPU"
	<linux-arm-msm@vger.kernel.org>
Subject: Re: [PATCH v15 0/6] usb: misc: Add onboard_usb_hub driver
Date: Tue, 19 Oct 2021 19:24:41 +0300	[thread overview]
Message-ID: <CAA8EJpq55e+fk9oDi8+JXDWiPcXDXK5oz1DL5eqfx+FkT-xhnw@mail.gmail.com> (raw)
In-Reply-To: <20210727004118.2583774-1-mka@chromium.org>

On Tue, 27 Jul 2021 at 03:41, Matthias Kaehlcke <mka@chromium.org> wrote:
>
> This series adds:
> - the onboard_usb_hub_driver
> - glue in the xhci-plat driver to create and destroy the
>   onboard_usb_hub platform devices if needed
> - a device tree binding for the Realtek RTS5411 USB hub controller
> - 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.

I have the feeling that you might want to check if you can use pwrseq
subsystem being proposed at
https://lore.kernel.org/linux-arm-msm/20211006035407.1147909-1-dmitry.baryshkov@linaro.org/.
It has been created for exactly the same reason of handling complex
power up/down requirements in a bus-neutral way. So instead of
creating an onboard-usb-hub, you might want to populate the hub node
with the reference to pwrseq device and make usb core call into
pwrseq. How does that sound to you?

>
> 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.


-- 
With best wishes
Dmitry

  parent reply	other threads:[~2021-10-19 16:24 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-27  0:41 Matthias Kaehlcke
2021-07-27  0:41 ` [PATCH v15 1/6] " Matthias Kaehlcke
2021-07-27  0:41 ` [PATCH v15 2/6] of/platform: Add stubs for of_platform_device_create/destroy() Matthias Kaehlcke
2021-07-27  0:41 ` [PATCH v15 3/6] arm64: defconfig: Explicitly enable USB_XHCI_PLATFORM Matthias Kaehlcke
2021-07-27  0:41 ` [PATCH v15 4/6] usb: Specify dependencies on USB_XHCI_PLATFORM with 'depends on' Matthias Kaehlcke
2021-07-27  0:41 ` [PATCH v15 5/6] usb: host: xhci-plat: Create platform device for onboard hubs in probe() Matthias Kaehlcke
2021-07-27  0:41 ` [PATCH v15 6/6] arm64: dts: qcom: sc7180-trogdor: Add nodes for onboard USB hub Matthias Kaehlcke
2021-08-09 15:49 ` [PATCH v15 0/6] usb: misc: Add onboard_usb_hub driver Matthias Kaehlcke
2021-08-11 12:38   ` Roger Quadros
2021-08-11 12:56     ` Roger Quadros
2021-08-12 17:08       ` Matthias Kaehlcke
2021-08-13  6:35         ` Roger Quadros
2021-08-13 18:33           ` Matthias Kaehlcke
2021-10-19 16:24 ` Dmitry Baryshkov [this message]
2021-10-19 22:54   ` Matthias Kaehlcke

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