On Wed, Feb 10, 2021 at 09:10:35AM -0800, Matthias Kaehlcke wrote: > This series adds the onboard_usb_hub_driver, the corresponding > device tree bindings and creation of onboard_usb_hub platform in > the xhci-plat driver during probe(). > > 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. It seems you are re-developing the power sequence drivers which perform exactly this. Peter Chen some time ago was bringing power sequence to USB devices, but I lost track where this ended up. Some of his (and my) very old work (2017...) can be found here: https://github.com/krzk/linux/tree/wip/odroid-u3-usb3503-pwrseq Instead of adding custom driver hiding some USB hub implementation, power sequence seems a generic solution. What if you need to power cycle other embedded USB device? Not a hub? I was not aware of previous discussions so maybe I am repeating someone. Best regards, Krzysztof
