Re: [PATCH 2/2] USB: misc: Add onboard_usb_hub driver

From: Matthias Kaehlcke
Date: Thu Sep 17 2020 - 12:21:13 EST

On Thu, Sep 17, 2020 at 01:24:30AM +0000, Peter Chen wrote:
> > > >
> > >
> > > You may need both (glue & xhci), it depends on system design, and
> > > usually, these two kinds of wakeup setting isn't conflict.
> >
> > Ok, thanks. So if I understand correctly the onboard hub driver should check the
> > wakeup state of the xHCI to determine if remote wakeup is enabled for the
> > controller (after all it doesn't know anything about the platform device).
> > Wakeup might not work properly if it is disabled for the platform device, but it's
> > the responsability of the board software/config to make sure it is enabled
> > (possibly this could be done by making the dwc3-qcom driver understand the
> > 'wakeup-source' property, as the xhci-mtk driver does).
> No, every level should handle its own wakeup setting. You may have to do this since the USB bus and platform bus
> are two different buses, you should not visit device structure across the bus. And you don't need a device tree property
> to do it. For platform driver, you could use device_may_wakeup, for onboard hub power driver, you could use
> usb_wakeup_enabled_descendants since you need to cover descendants.
> The purpose of these two wakeup logic is different, for USB bus, it is used to tell USB devices to enable remote wakeup
> and do not power off its regulator; for platform bus, it is used to tell the controller to enable its wakeup setting and keep
> the regulator for its USB controller and USB PHY (if needed).

Sorry, I didn't express myself clearly. With the platform device I was
referring to the dwc3-qcom ('glue') in this case, which could check
it's own 'wakeup-source' attribute to enable wakeup at boot. The driver
currently enables wakeup statically. The onboard_hub driver is agnostic
of this device.