RE: [PATCH] ACPI: Execute the _PTS method when system reboot

From: Ocean HY1 He
Date: Thu Jun 23 2016 - 08:56:55 EST


Hi Rafael,
Please see my reply in below.

Regards,
Ocean He
SW Development Dept.
Beijing Design Center
Enterprise Product Group
Mobile: 18911778926
E-mail: hehy1@xxxxxxxxxx
No.6 Chuang Ye Road, Haidian District, Beijing, China 100085

> -----Original Message-----
> From: Rafael J. Wysocki [mailto:rjw@xxxxxxxxxxxxx]
> Sent: Wednesday, June 22, 2016 7:56 AM
> To: Ocean HY1 He
> Cc: lenb@xxxxxxxxxx; linux-acpi@xxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx; David Tanaka; Nagananda Chumbalkar
> Subject: Re: [PATCH] ACPI: Execute the _PTS method when system reboot
>
> On Monday, May 09, 2016 05:50:11 AM Ocean HY1 He wrote:
> > The _PTS control method is defined in the section 7.4.1 of acpi 6.0
> > spec. The _PTS control method is executed by the OS during the sleep
> > transition process for S1, S2, S3, S4, and for orderly S5 shutdown.
> > The sleeping state value (For example, 1, 2, 3, 4 or 5 for the S5
> > soft-off state) is passed to the _PTS control method. This method
> > is called after OSPM has notified native device drivers of the sleep
> > state transition and before the OSPM has had a chance to fully
> > prepare the system for a sleep state transition.
> >
> > The _PTS control method provides the BIOS a mechanism for performing
> > some housekeeping, such as writing the sleep type value to the
> embedded
> > controller, before entering the system sleeping state.
> >
> > According to section 7.5 of acpi 6.0 spec, _PTS should run after _TTS.
> >
> > Thus, a _PTS block notifier is added to the reboot notifier list so that
> > the _PTS object will also be evaluated when the system reboot.
>
> So I understand why it may be necessary to evaluate _PTS before entering
> S5,
> but I'm totally unsure about reboot.
>
> What does reboot have to do with S5?
>
In ACPI spec, there is no explicit words saying _PTS should be
executed when reboot. But reboot could be equal to the
process S0->S5->S0. Thus _PTS should be executed when reboot.

I am thinking this is the same as _TTS. In ACPI spec, there is also
no explicit words saying _TTS should be executed when reboot.
But kernel executes _TTS when reboot indeed.

> > Signed-off-by: Ocean He <hehy1@xxxxxxxxxx>
> > Signed-off-by: Nagananda Chumbalkar <nchumbalkar@xxxxxxxxxx>
> > ---
> > drivers/acpi/sleep.c | 27 +++++++++++++++++++++++++++
> > 1 file changed, 27 insertions(+)
> >
> > diff --git a/drivers/acpi/sleep.c b/drivers/acpi/sleep.c
> > index 2a8b596..8b290fb 100644
> > --- a/drivers/acpi/sleep.c
> > +++ b/drivers/acpi/sleep.c
> > @@ -55,6 +55,26 @@ static struct notifier_block tts_notifier = {
> > .priority = 0,
> > };
> >
> > +static int pts_notify_reboot(struct notifier_block *this,
> > + unsigned long code, void *x)
> > +{
> > + acpi_status status;
> > +
> > + status = acpi_execute_simple_method(NULL, "\\_PTS",
> ACPI_STATE_S5);
> > + if (ACPI_FAILURE(status) && status != AE_NOT_FOUND) {
> > + /* It won't break anything. */
> > + printk(KERN_NOTICE "Failure in evaluating _PTS object\n");
> > + }
> > +
> > + return NOTIFY_DONE;
> > +}
> > +
> > +static struct notifier_block pts_notifier = {
> > + .notifier_call = pts_notify_reboot,
> > + .next = NULL,
> > + .priority = 0,
> > +};
> > +
> > static int acpi_sleep_prepare(u32 acpi_state)
> > {
> > #ifdef CONFIG_ACPI_SLEEP
> > @@ -896,5 +916,12 @@ int __init acpi_sleep_init(void)
> > * object can also be evaluated when the system enters S5.
> > */
> > register_reboot_notifier(&tts_notifier);
> > +
> > + /*
> > + * According to section 7.5 of acpi 6.0 spec, _PTS should run after
> > + * _TTS when the system enters S5.
> > + */
> > + register_reboot_notifier(&pts_notifier);
>
> Why do you have to add a second notifier?
>
> Why can't _TTS and _PTS be evaluated from one notifier?
>
If execute _PTS method in tts_notify_reboot(), then it would break
definition of tts_notify_reboot(). My intention is to keep new codes
has limited impact on existed codes.
Of course, it's possible to merge _TTS and _PTS into one unified notifier.
The advantage is more actions could be added into the unified notifier in future.
Which way you prefer?
> > +
> > return 0;
> > }
> >
>
> Thanks,
> Rafael