On Tue, Jul 8, 2025 at 4:37 PM Mario Limonciello
<mario.limoncie...@amd.com> wrote:
>
> On 7/8/2025 3:42 AM, Samuel Zhang wrote:
> > dev_pm_ops.thaw() is called in following cases:
> > * normal case: after hibernation image has been created.
> > * error case 1: creation of a hibernation image has failed.
> > * error case 2: restoration from a hibernation image has failed.
> >
> > For normal case, it is called mainly for resume storage devices for
> > saving the hibernation image. Other devices that are not involved
> > in the image saving do not need to resume the device. But since there's
> > no api to know which case thaw() is called, device drivers can't
> > conditionally resume device in thaw().
> >
> > The new pm_transition_event() is such a api to query if thaw() is called
> > in normal case. The returned value in thaw() is:
> > * PM_EVENT_THAW: normal case, no need to resume non-storage devices.
> > * PM_EVENT_RECOVER: error case, need to resume devices.
> >
> > Signed-off-by: Samuel Zhang <guoqing.zh...@amd.com>
> > ---
> > drivers/base/power/main.c | 5 +++++
> > include/linux/pm.h | 16 ++++++++++++++++
> > 2 files changed, 21 insertions(+)
> >
> > diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
> > index 40e1d8d8a589..7e0982caa4d4 100644
> > --- a/drivers/base/power/main.c
> > +++ b/drivers/base/power/main.c
> > @@ -62,6 +62,11 @@ static LIST_HEAD(dpm_noirq_list);
> >
> > static DEFINE_MUTEX(dpm_list_mtx);
> > static pm_message_t pm_transition;
> > +int pm_transition_event(void)
> > +{
> > + return pm_transition.event;
> > +}
> > +EXPORT_SYMBOL_GPL(pm_transition_event);
> >
> > static int async_error;
> >
> > diff --git a/include/linux/pm.h b/include/linux/pm.h
> > index 78855d794342..d1cb77ede1a2 100644
> > --- a/include/linux/pm.h
> > +++ b/include/linux/pm.h
> > @@ -657,6 +657,22 @@ struct pm_subsys_data {
> > #define DPM_FLAG_SMART_SUSPEND BIT(2)
> > #define DPM_FLAG_MAY_SKIP_RESUME BIT(3)
> >
> > +/**
> > + * pm_transition_event() - Query the current pm transition event value.
> > + *
> > + * Used to query the reason why thaw() is called. It will be one of 2
> > values:
> > + *
> > + * PM_EVENT_THAW: normal case.
> > + * hibernation image has been created.
> > + *
> > + * PM_EVENT_RECOVER: error case.
> > + * creation of a hibernation image or restoration of the main
> > memory
> > + * contents from a hibernation image has failed.
>
> I don't believe this documentation is complete. In the use in this
> series those are two events used, but as this is now exported this might
> be used by other callers later which could use it for other PM_EVENT_*.
>
> So because of this I think it's best to convert the comment in
> include/linux/pm.h to kdoc and then reference that from this kdoc.
+1
> > + *
> > + * Return: PM_EVENT_ messages
> > + */
> > +int pm_transition_event(void);
> > +
> > struct dev_pm_info {
> > pm_message_t power_state;
> > bool can_wakeup:1;
>
