Re: [PATCH v4 1/5] usb: dwc3: separate dev_pm_ops for each pm_event

[Guan-Yu Lin <guanyulin@xxxxxxxxxx>]

On Wed, Oct 9, 2024 at 8:45 PM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
>
> On Wed, Oct 09, 2024 at 05:42:55AM +0000, Guan-Yu Lin wrote:
> > +
> > +static int dwc3_poweroff(struct device *dev)
> > +{
> > +     struct dwc3     *dwc = dev_get_drvdata(dev);
> > +     int             ret;
> > +
> > +     ret = dwc3_suspend_common(dwc, PMSG_HIBERNATE);
>
> Why is power off hibernate?
>
> This needs an ack from the dwc3 maintainer as I can't determine if it's
> correct at all...
>
> thanks,
>
> greg k-h

Described in /include/linux/pm.h, PM_EVENT_HIBERNATE message denotes
the following transition in the PM core code:
"Hibernation image has been saved, call ->prepare() and ->poweroff()
for all devices."
Meantime, the interpretation of the the above description could be
found in /drivers/base/power/main.c:
static pm_callback_t pm_op(const struct dev_pm_ops *ops, pm_message_t state)
{
...
        case PM_EVENT_HIBERNATE:
                return ops->poweroff;
...
}
An example in device drivers could be found in usb/drivers/usb/core/usb.c:
static int usb_dev_suspend(struct device *dev)
{
        return usb_suspend(dev, PMSG_SUSPEND);
}

Regards,
Guan-Yu