Hi Matthias,
On Fri, Apr 29, 2022 at 12:19:22PM -0700, Matthias Kaehlcke wrote:
> Hi Pavan,
>
> On Fri, Apr 29, 2022 at 06:29:56PM +0530, Pavan Kondeti wrote:
> > Hi Matthias,
> >
> > On Mon, Apr 25, 2022 at 06:33:03PM +0530, Pavan Kondeti wrote:
> > > Hi Matthias,
> > >
> > > On Fri, Apr 22, 2022 at 11:44:36AM -0700, Matthias Kaehlcke wrote:
> > > > On Fri, Apr 22, 2022 at 01:57:17PM +0200, Rafael J. Wysocki wrote:
> > > > > On Tue, Apr 19, 2022 at 9:11 PM Sandeep Maheswaram
> > > > > <quic_c_sanm@xxxxxxxxxxx> wrote:
> > > > > >
> > > > > > From: Matthias Kaehlcke <mka@xxxxxxxxxxxx>
> > > > > >
> > > > > > Add device_children_wakeup_capable() which checks whether the device itself
> > > > > > or one if its descendants is wakeup capable.
> > > > >
> > > > > device_wakeup_path() exists for a very similar purpose.
> > > > >
> > > > > Is it not usable for whatever you need the new function introduced here?
> > > >
> > > > I wasn't aware of it's function, there are no doc comments and the
> > > > name isn't really self explanatory.
> > > >
> > > > In a quick test device_wakeup_path() returned inconsistent values for the
> > > > root hub, sometimes true, others false when a wakeup capable USB device was
> > > > connected.
> > >
> > > We will also test the same to double confirm the behavior of
> > > device_wakeup_path(). I am assuming that you checked device_wakeup_path()
> > > only during system suspend path.
> > >
> > > Here is what I understood by looking at __device_suspend(). Please share
> > > your thoughts on this.
> > >
> > > power.wakeup_path is set to true for the parent *after* a wakeup capable
> > > device is suspended. This means when the root hub(s) is suspended, it is
> > > propagated to xhci-plat and when xhci-plat is suspended, it is propagated
> > > to dwc3. bottom up propgation during system suspend.
> > >
> > > I believe we can directly check something like this in the dwc3 driver
> > > instead of having another wrapper like device_children_wakeup_capable().
> > >
> > > diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> > > index 1170b80..a783257 100644
> > > --- a/drivers/usb/dwc3/core.c
> > > +++ b/drivers/usb/dwc3/core.c
> > > @@ -1878,8 +1878,14 @@ static int dwc3_suspend_common(struct dwc3 *dwc, pm_message_t msg)
> > > break;
> > > case DWC3_GCTL_PRTCAP_HOST:
> > > if (!PMSG_IS_AUTO(msg)) {
> > > + /*
> > > + * Don't kill the host when dwc3 is wakeup capable and
> > > + * its children needs wakeup.
> > > + */
> > > + if (device_may_wakeup(dwc->dev) && device_wakeup_path(dwc->dev))
> > > + handle_it();
> > > + } else {
> > > dwc3_core_exit(dwc);
> > > - break;
> > > }
> > >
> > > /* Let controller to suspend HSPHY before PHY driver suspends */
> > >
> >
> > device_wakeup_path(dwc->dev) is returning true all the time irrespective of
> > the wakeup capability (and enabled status) of the connected USB devices. That
> > is because xhci-plat device is configured to wakeup all the time. Since the
> > child is wakeup capable, its parent i.e dwc3 has device_wakeup_path() set.
> > device_children_wakeup_capable() will also suffer the problem. However,
> >
> > device_children_wakeup_capable(&hcd->self.root_hub->dev) is what Sandeep's
> > patch is using. That is not correct. we have two root hubs (HS and SS) associated
> > with a USB3 controller and calling it on one root hub is incorrect.
> > device_children_wakeup_capable() must be called on xhci-plat so that it covers
> > both HS and SS root hubs
>
> Thanks for pointing that out!
>
> > I am thinking of dynamically enabling/disabling xhci-plat wakeup capability so
> > that the wakeup path is correctly propagated to dwc3. something like below.
> > Does it make sense to you?
> >
> > diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
> > index 649ffd8..be0c55b 100644
> > --- a/drivers/usb/host/xhci-plat.c
> > +++ b/drivers/usb/host/xhci-plat.c
> > @@ -412,6 +412,9 @@ static int __maybe_unused xhci_plat_suspend(struct device *dev)
> > struct xhci_hcd *xhci = hcd_to_xhci(hcd);
> > int ret;
> >
> > + if (!device_wakeup_path(dev))
> > + device_wakeup_disable(dev);
> > +
> > if (pm_runtime_suspended(dev))
> > pm_runtime_resume(dev);
> >
> > @@ -443,6 +446,8 @@ static int __maybe_unused xhci_plat_resume(struct device *dev)
> > pm_runtime_set_active(dev);
> > pm_runtime_enable(dev);
> >
> > + device_wakeup_enable(dev);
>
> I think this also needs to be done conditionally, otherwise it would
> create a new wake source on every resume when wakeup is already
> enabled.
>
Right, this needs to be done conditionally. However, there is a silent
warning inside device_wakeup_enable() if it is called during system
transition. Not sure if we really need to worry about that or not.
Thanks,
Pavan
