Re: [PATCH v4 3/3] usb: xhci: plat: Facilitate using autosuspend for xhci plat devices

[Krishna Kurapati]

On 8/13/2025 11:46 AM, Peter Chen wrote:
> On Tue, Aug 12, 2025 at 1:58 PM Krishna Kurapati
> <krishna.kurapati@xxxxxxxxxxxxxxxx> wrote:
> > Allow autosuspend to be used by xhci plat device. For Qualcomm SoCs,
> > when in host mode, it is intended that the controller goes to suspend
> > state to save power and wait for interrupts from connected peripheral
> > to wake it up. This is particularly used in cases where a HID or Audio
> > device is connected. In such scenarios, the usb controller can enter
> > auto suspend and resume action after getting interrupts from the
> > connected device.
> >
> > Signed-off-by: Krishna Kurapati <krishna.kurapati@xxxxxxxxxxxxxxxx>
> > ---
> >   drivers/usb/host/xhci-plat.c | 1 +
> >   1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
> > index 5eb51797de32..dd57ffedcaa2 100644
> > --- a/drivers/usb/host/xhci-plat.c
> > +++ b/drivers/usb/host/xhci-plat.c
> > @@ -171,6 +171,7 @@ int xhci_plat_probe(struct platform_device *pdev, struct device *sysdev, const s
> >                  return ret;
> >
> >          pm_runtime_set_active(&pdev->dev);
> > +       pm_runtime_use_autosuspend(&pdev->dev);
> >          pm_runtime_enable(&pdev->dev);
> >          pm_runtime_get_noresume(&pdev->dev);
>
> There is an xhci quirk XHCI_DEFAULT_PM_RUNTIME_ALLOW for it, try to use it.

Hi Peter,

I see it being used only in xhci-pci.c.

In xhci-plat, I intended to only allow usage of autosuspend and let 
userspace decide whether to use it or not (echo (auto or on) > control).

Hence I only did use_autosuspend() instead of doing runtime_allow.

Regards,
Krishna,