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

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Date:	Thu, 23 Jun 2016 12:55:54 +0000
From:	Ocean HY1 He <hehy1@...ovo.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
CC:	"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>
Subject: RE: [PATCH] ACPI: Execute the _PTS method when system reboot

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. 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@...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(). 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