From: "Chen, Yu C" <yu.c.chen@intel.com>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>
CC: "Rafael J. Wysocki" <rafael@kernel.org>,
        ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
        "x86@kernel.org" <x86@kernel.org>,
        "linux-efi@vger.kernel.org" <linux-efi@vger.kernel.org>,
        "Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
        "linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
        Len Brown <lenb@kernel.org>, Matt Fleming <matt@codeblueprint.co.uk>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, "Zhang, Rui" <rui.zhang@intel.com>
Subject: RE: [PATCH][RFC v3] ACPI / PM: Fix poweroff issue on HW-full
 platforms without _S5
Thread-Topic: [PATCH][RFC v3] ACPI / PM: Fix poweroff issue on HW-full
 platforms without _S5
Thread-Index: AQHReBtTuYTrZFDLZkGy2iiQCJLNIJ9NcY+AgACwtaCAACIcAIABZrTQ///6MgCAAk9ZkA==
Date: Thu, 10 Mar 2016 02:16:44 +0000
Message-ID: <36DF59CE26D8EE47B0655C516E9CE640286D3E69@shsmsx102.ccr.corp.intel.com>
References: <1457319045-25434-1-git-send-email-yu.c.chen@intel.com>
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 <36DF59CE26D8EE47B0655C516E9CE640286D370A@shsmsx102.ccr.corp.intel.com>
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> -----Original Message-----
> From: Rafael J. Wysocki [mailto:rjw@rjwysocki.net]
> Sent: Wednesday, March 09, 2016 6:57 AM
> To: Chen, Yu C
> Cc: Rafael J. Wysocki; ACPI Devel Maling List; x86@kernel.org; linux-
> efi@vger.kernel.org; Linux Kernel Mailing List; linux-pm@vger.kernel.org;
> Len Brown; Matt Fleming; Thomas Gleixner; Ingo Molnar; H. Peter Anvin;
> Zhang, Rui
> Subject: Re: [PATCH][RFC v3] ACPI / PM: Fix poweroff issue on HW-full
> platforms without _S5
> 
> On Tuesday, March 08, 2016 04:25:30 PM Chen, Yu C wrote:
> > > -----Original Message-----
> > > From: linux-pm-owner@vger.kernel.org [mailto:linux-pm-
> > > owner@vger.kernel.org] On Behalf Of Rafael J. Wysocki
> > > Sent: Tuesday, March 08, 2016 9:54 AM
> > > To: Chen, Yu C
> > > Cc: Rafael J. Wysocki; ACPI Devel Maling List; x86@kernel.org;
> > > linux- efi@vger.kernel.org; Linux Kernel Mailing List;
> > > linux-pm@vger.kernel.org; Len Brown; Matt Fleming; Thomas Gleixner;
> > > Ingo Molnar; H. Peter Anvin; Zhang, Rui
> > > Subject: Re: [PATCH][RFC v3] ACPI / PM: Fix poweroff issue on
> > > HW-full platforms without _S5
> > >
> > > On Monday, March 07, 2016 03:53:13 PM Chen, Yu C wrote:
> > > > Hi Rafael,
> > > > (resend for broken content)
> > > >
> > > > > -----Original Message-----
> > > > > From: rjwysocki@gmail.com [mailto:rjwysocki@gmail.com] On Behalf
> > > > > Of Rafael J. Wysocki
> > > > > Sent: Monday, March 07, 2016 9:19 PM
> > > > > To: Chen, Yu C
> > > > > Cc: ACPI Devel Maling List; x86@kernel.org;
> > > > > linux-efi@vger.kernel.org; Linux Kernel Mailing List;
> > > > > linux-pm@vger.kernel.org; Rafael J. Wysocki; Len Brown; Matt
> > > > > Fleming; Thomas Gleixner; Ingo Molnar; H. Peter Anvin; Zhang,
> > > > > Rui
> > > > > Subject: Re: [PATCH][RFC v3] ACPI / PM: Fix poweroff issue on
> > > > > HW-full platforms without _S5
> > > > >
> > > > [cut]
> > > > > >  bool efi_poweroff_required(void)  {
> > > > > > -       return !!acpi_gbl_reduced_hardware;
> > > > > > +       return acpi_gbl_reduced_hardware || (acpi_no_s5 &&
> > > > > > + !pm_power_off);
> > > > >
> > > > > What if CONFIG_ACPI is not set here?
> > > > If CONFIG_ACPI is not set, this file would not be compiled,
> > > > because CONFIG_EFI depends on CONFIG_ACPI.
> > >
> > > OK
> > >
> > > So the next question will be if efi_poweroff_required() is
> > > guaranteed to run after all of the other code that may register alternative
> power off handling.
> > Hum. unfortunately it is not guaranteed to run after all of the other
> > code, because other components who register pm_power_off may be
> built as modules, and
> > we can not predict/control the sequence registration.   So this patch may
> > break the EFI platforms who use non-efi poweroff due to unstable EFI
> > service ,  not sure if there are any released-products of this kind.
> >
> > Currently I'm thinking of 3 possible solutions,  could you please give some
> advices on them:
> >
> > 1. Introduce bootopt of 'poweroff=efi'
> >      Set the pm_power_off to efi_power_off no matter whether there is
> > _S5 or not
> >
> > 2. Introduce /sys/power/poweroff
> >     Allow the user to choose which  pm_power_off, for example:
> >
> > # cat /sys/power/poweroff
> > *acpi		acpi_power_off
> > efi		efi_power_off
> > gpio		gpio_poweroff_do_poweroff
> > user can echo string to enable which one.
> >
> > And two APIs:
> > register_power_off(char *name, power_off func)
> > unregister_power_off(char *name)
> >
> >
> > 3. replace all the codes of  pm_power_off() with
> > reliable_pm_power_off()
> >
> > void reliable_pm_power_off(void)
> > {
> > 	if (!pm_power_off) {
> > 		if (acpi_no_s5)
> > 			pm_power_off = efi_power_off;
> > 	/* Other conditions added in the future. */
> > 	}
> > 	pm_power_off();
> > }
> 
> What about something like adding something like default_power_off that
> would be used by pm_power_off if nothing else is available?
OK,  I'll try another version, in which other components can set  its default_power_off,
then pm_power_off has a chance to be set to default_power_off if pm_power_off is NULL.