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
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);
+
return 0;
}
Thanks,
Pavan
