linux-kernel - RE: [PATCH] ACPI: Execute the

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Date:	Fri, 24 Jun 2016 02:59:24 +0000
From:	Ocean HY1 He <hehy1@...ovo.com>
To:	"Rafael J. Wysocki" <rafael@...nel.org>
CC:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"lenb@...nel.org" <lenb@...nel.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	David Tanaka <dtanaka@...ovo.com>,
	Nagananda Chumbalkar <nchumbalkar@...ovo.com>,
	"Zheng, Lv" <lv.zheng@...el.com>,
	Sumeet Kochar <skochar@...ovo.com>
Subject: RE: [PATCH] ACPI: Execute the _PTS method when system reboot



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


> -----Original Message-----
> From: rjwysocki@...il.com [mailto:rjwysocki@...il.com] On Behalf Of
> Rafael J. Wysocki
> Sent: Thursday, June 23, 2016 9:13 PM
> To: Ocean HY1 He
> Cc: Rafael J. Wysocki; lenb@...nel.org; linux-acpi@...r.kernel.org;
> linux-kernel@...r.kernel.org; David Tanaka; Nagananda Chumbalkar
> Subject: Re: [PATCH] ACPI: Execute the _PTS method when system reboot
> 
> On Thu, Jun 23, 2016 at 2:55 PM, Ocean HY1 He <hehy1@...ovo.com>
> wrote:
> > 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@...ovo.com
> > No.6 Chuang Ye Road, Haidian District, Beijing, China 100085
> >
> >> -----Original Message-----
> >> From: Rafael J. Wysocki [mailto:rjw@...ysocki.net]
> >> Sent: Wednesday, June 22, 2016 7:56 AM
> >> To: Ocean HY1 He
> >> Cc: lenb@...nel.org; linux-acpi@...r.kernel.org;
> >> linux-kernel@...r.kernel.org; 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.
> 
> Not in general.
> 
> In particular, wakeup devices that would be set up for S5 need not be
> set up for that.  Also the mechanism by which transitions to S5 are
> entered is different from the reboot one, at least from the OS
> perspective.
> 
> > Thus _PTS should be executed when reboot.
> 
> No, it doesn't follow.
> 
> > 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.
> 
> Yes, it does.  Maybe it shouldn't?
> 
> It may not hurt to call _PTS before reboot too, but is it guaranteed
> to work across the board on all systems everywhere?
> 
I try to clarify the key point of this case: does devices should go to S5(shutdown) when reboot?

I think the answer is yes. 
And It has no hurt to let devices go to S5 before reboot is invoked, here is the reasons:
#1 The new _PTS codes block nothing thus reboot can be guaranteed to be invoked eventually.
#2. Devices are mandatory to support S5 state, this means go to S5 could be a safe trip.
#3 Reboot would cause devices re-initialization from the scratch.

What's your decision then? ;-)

Regards,
Ocean.

> >> > Signed-off-by: Ocean He <hehy1@...ovo.com>
> >> > Signed-off-by: Nagananda Chumbalkar <nchumbalkar@...ovo.com>
> >> > ---
> >> >  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().
> 
> What exactly would it break?
> 
> > My intention is to keep new codes
> > has limited impact on existed codes.
> 
> Even if that makes a little sense?
> 
> > 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?
> 
> I would just use one notifier.
I follow you.
> 
> Thanks,
> Rafael