On Mon, May 09, 2022 at 09:02:38AM +0530, Pavan Kondeti wrote:
> On Fri, May 06, 2022 at 04:30:33PM -0400, Alan Stern wrote:
> > On Fri, May 06, 2022 at 11:46:06AM -0700, Matthias Kaehlcke wrote:
> > > Currently the core/PHYs are always powered off during suspend in host mode:
> > >
> > > static int dwc3_suspend_common(struct dwc3 *dwc, pm_message_t msg)
> > > {
> > > ...
> > >
> > > switch (dwc->current_dr_role) {
> > > case DWC3_GCTL_PRTCAP_HOST:
> > > if (!PMSG_IS_AUTO(msg)) {
> > > dwc3_core_exit(dwc);
> > > break;
> > > }
> > >
> > > ...
> > > }
> > >
> > > With that I would expect wakeup to be broken for all dwc3. I'm a bit confused
> > > though, since dwc3-imx8mp.c seems to support wakeup and the driver landed
> > > after the above patch ...
> > >
> > > This series intends to change the above code to something like this:
> > >
> > > if (!PMSG_IS_AUTO(msg)) {
> > > if (device_may_wakeup(dwc->dev) &&
> > > device_wakeup_path(dwc->dev)) {
> > > dwc->phy_power_off = false;
> > > } else {
> > > dwc->phy_power_off = true;
> > > dwc3_core_exit(dwc);
> > > }
> > > }
> >
> > > i.e. the core/PHYs would only be powered down if wakeup is disabled or no
> > > wakeup capable devices are connected. With that plug/unplug events still
> > > wouldn't be detected.
> >
> > Indeed. Shouldn't the "&&" and "||"? That is, don't you want to leave
> > the core and PHY powered if wakeup is enabled for the root hub or for
> > any devices beneath it?
> >
> > It would be simpler to leave the core and PHY powered whenever wakeup is
> > enabled for the controller itself, regardless of the status of the root
> > hub and downstream devices. Users might not like this so much if the
> > default setting is to enable wakeup for the controller always. Still,
> > it's an easy solution.
> >
> At this point it is not clear if all boards that has DWC3 controller can
> support wakeup capability or not. Thats why we have introduced a wakeup device
> tree property based on which we advertise our wakeup capability.
>
> device_init_wakeup(&pdev->dev, of_property_read_bool(dev->of_node,
> "wakeup-source"));
>
> Hence the && condition to make sure that we support wakeup and our children
> needs it.
Oh, I see. I misread the code above, thinking that dwc->dev referred to
the root hub. It doesn't; it refers to the controller. Sorry for the
mistake.
BTW, if there's any trouble with getting device_wakeup_path() to work
the way you want, you could consider instead calling
usb_wakeup_enabled_descendants() on the root hub. This function returns
a count of the number of wakeup-enabled USB devices at or below the
device you pass to it.
Alan Stern
