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Re: [PATCH/RFC 3/6] drivers: firmware: psci: Implement shallow suspend mode

From Mark Rutland <mark.rutland@arm.com>
Newsgroups linux.kernel
Subject Re: [PATCH/RFC 3/6] drivers: firmware: psci: Implement shallow suspend mode
Date 2017-02-21 18:30 +0100
Message-ID <tdmqd-5F2-7@gated-at.bofh.it> (permalink)
References <td2Uy-Zo-11@gated-at.bofh.it> <td2Uy-Zo-19@gated-at.bofh.it> <tdgut-1L2-13@gated-at.bofh.it> <tdgEa-1QZ-7@gated-at.bofh.it> <tdlDP-55Q-1@gated-at.bofh.it>
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Hi,

On Tue, Feb 21, 2017 at 05:32:50PM +0100, Geert Uytterhoeven wrote:
> On Tue, Feb 21, 2017 at 12:14 PM, Sudeep Holla <sudeep.holla@arm.com> wrote:
> > On 21/02/17 11:07, Pavel Machek wrote:
> >>> Enable support for "shallow" suspend mode, also known as "Standby" or
> >>> "Power-On Suspend".
> >>>
> >>> As secondary CPU cores are taken offline, "shallow" suspend mode saves
> >>> slightly more power than "s2idle", but less than "deep" suspend mode.
> >>> However, unlike "deep" suspend mode, "shallow" suspend mode can be used
> >>> regardless of the presence of support for PSCI_SYSTEM_SUSPEND, which is
> >>> an optional API in PSCI v1.0.
> >>
> >> If system supports "shallow" suspend, why does not PSCI implement it?
> >
> > Yes it can, and IIUC it already does on this platform with CPU_SUSPEND.
> > All it now needs is just to use existing "freeze" suspend mode in Linux.
> 
> How can Linux know if using "deep" suspend will allow to wake-up the system
> according to configured wake-up sources, or not?

My understanding is that if a device can wake the system from
PSCI_SYSTEM_SUSPEND, it should be described in the DT as a wakeup source
[1]. So we should be able to determine the set of devices which can wake
the system from a suspend. We shouldn't assume that other devices can
(though I don't precisely what we do currently).

Otherwise, where PSCI_CPU_SUSPEND, we'd expect that most devices
(barring cpu-local timers) can wake up CPUs, and hence the system, by
raising an interrupt.

Thanks,
Mark.

[1] Documentation/devicetree/bindings/power/wakeup-source.txt

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[PATCH/RFC 0/6] PSCI: Fix non-PMIC wake-up if SYSTEM_SUSPEND cuts power Geert Uytterhoeven <geert+renesas@glider.be> - 2017-02-20 21:40 +0100
  [PATCH/RFC 2/6] PM / Wakeup: Add wakeup_source_available() Geert Uytterhoeven <geert+renesas@glider.be> - 2017-02-20 21:40 +0100
  [PATCH/RFC 3/6] drivers: firmware: psci: Implement shallow suspend mode Geert Uytterhoeven <geert+renesas@glider.be> - 2017-02-20 21:40 +0100
    Re: [PATCH/RFC 3/6] drivers: firmware: psci: Implement shallow  suspend mode Sudeep Holla <sudeep.holla@arm.com> - 2017-02-21 11:50 +0100
      Re: [PATCH/RFC 3/6] drivers: firmware: psci: Implement shallow  suspend mode Geert Uytterhoeven <geert@linux-m68k.org> - 2017-02-21 17:30 +0100
        Re: [PATCH/RFC 3/6] drivers: firmware: psci: Implement shallow  suspend mode Sudeep Holla <sudeep.holla@arm.com> - 2017-02-21 18:00 +0100
    Re: [PATCH/RFC 3/6] drivers: firmware: psci: Implement shallow  suspend mode Pavel Machek <pavel@ucw.cz> - 2017-02-21 12:10 +0100
      Re: [PATCH/RFC 3/6] drivers: firmware: psci: Implement shallow  suspend mode Sudeep Holla <sudeep.holla@arm.com> - 2017-02-21 12:20 +0100
        Re: [PATCH/RFC 3/6] drivers: firmware: psci: Implement shallow  suspend mode Geert Uytterhoeven <geert@linux-m68k.org> - 2017-02-21 17:40 +0100
          Re: [PATCH/RFC 3/6] drivers: firmware: psci: Implement shallow  suspend mode Sudeep Holla <sudeep.holla@arm.com> - 2017-02-21 18:30 +0100
            Re: [PATCH/RFC 3/6] drivers: firmware: psci: Implement shallow  suspend mode Geert Uytterhoeven <geert@linux-m68k.org> - 2017-02-22 14:50 +0100
              Re: [PATCH/RFC 3/6] drivers: firmware: psci: Implement shallow  suspend mode Sudeep Holla <sudeep.holla@arm.com> - 2017-02-22 15:40 +0100
          Re: [PATCH/RFC 3/6] drivers: firmware: psci: Implement shallow  suspend mode Mark Rutland <mark.rutland@arm.com> - 2017-02-21 18:30 +0100
            Re: [PATCH/RFC 3/6] drivers: firmware: psci: Implement shallow  suspend mode Geert Uytterhoeven <geert@linux-m68k.org> - 2017-02-21 19:10 +0100
              Re: [PATCH/RFC 3/6] drivers: firmware: psci: Implement shallow  suspend mode Mark Rutland <mark.rutland@arm.com> - 2017-02-21 19:20 +0100
                Re: [PATCH/RFC 3/6] drivers: firmware: psci: Implement shallow  suspend mode Geert Uytterhoeven <geert@linux-m68k.org> - 2017-02-21 19:30 +0100
  [PATCH/RFC 1/6] alarmtimer: Postpone wake-up source registration until really available Geert Uytterhoeven <geert+renesas@glider.be> - 2017-02-20 21:40 +0100
  [PATCH/RFC 6/6] arm64: dts: r8a7796: Fix non-PMIC wake-up sources Geert Uytterhoeven <geert+renesas@glider.be> - 2017-02-20 21:40 +0100
  [PATCH/RFC 4/6] drivers: firmware: psci: Fix non-PMIC wake-up if SYSTEM_SUSPEND cuts power Geert Uytterhoeven <geert+renesas@glider.be> - 2017-02-20 21:40 +0100
    Re: [PATCH/RFC 4/6] drivers: firmware: psci: Fix non-PMIC wake-up if  SYSTEM_SUSPEND cuts power Sudeep Holla <sudeep.holla@arm.com> - 2017-02-21 12:00 +0100
      Re: [PATCH/RFC 4/6] drivers: firmware: psci: Fix non-PMIC wake-up if  SYSTEM_SUSPEND cuts power Geert Uytterhoeven <geert@linux-m68k.org> - 2017-02-21 17:40 +0100
        Re: [PATCH/RFC 4/6] drivers: firmware: psci: Fix non-PMIC wake-up if  SYSTEM_SUSPEND cuts power Sudeep Holla <sudeep.holla@arm.com> - 2017-02-21 17:50 +0100
    Re: [PATCH/RFC 4/6] drivers: firmware: psci: Fix non-PMIC wake-up if  SYSTEM_SUSPEND cuts power Pavel Machek <pavel@ucw.cz> - 2017-02-21 12:10 +0100
      Re: [PATCH/RFC 4/6] drivers: firmware: psci: Fix non-PMIC wake-up if  SYSTEM_SUSPEND cuts power Geert Uytterhoeven <geert@linux-m68k.org> - 2017-02-21 17:40 +0100
      Re: [PATCH/RFC 4/6] drivers: firmware: psci: Fix non-PMIC wake-up if  SYSTEM_SUSPEND cuts power Mark Rutland <mark.rutland@arm.com> - 2017-02-21 19:00 +0100
    Re: [PATCH/RFC 4/6] drivers: firmware: psci: Fix non-PMIC wake-up if  SYSTEM_SUSPEND cuts power Mark Rutland <mark.rutland@arm.com> - 2017-02-21 18:50 +0100
      Re: [PATCH/RFC 4/6] drivers: firmware: psci: Fix non-PMIC wake-up if  SYSTEM_SUSPEND cuts power Geert Uytterhoeven <geert@linux-m68k.org> - 2017-02-22 15:10 +0100
        Re: [PATCH/RFC 4/6] drivers: firmware: psci: Fix non-PMIC wake-up if  SYSTEM_SUSPEND cuts power "Rafael J. Wysocki" <rafael@kernel.org> - 2017-02-22 16:00 +0100
  Re: [PATCH/RFC 0/6] PSCI: Fix non-PMIC wake-up if SYSTEM_SUSPEND cuts  power Sudeep Holla <sudeep.holla@arm.com> - 2017-02-21 11:40 +0100
    Re: [PATCH/RFC 0/6] PSCI: Fix non-PMIC wake-up if SYSTEM_SUSPEND cuts power Geert Uytterhoeven <geert@linux-m68k.org> - 2017-02-21 17:30 +0100
      Re: [PATCH/RFC 0/6] PSCI: Fix non-PMIC wake-up if SYSTEM_SUSPEND cuts  power Sudeep Holla <sudeep.holla@arm.com> - 2017-02-21 17:50 +0100
        Re: [PATCH/RFC 0/6] PSCI: Fix non-PMIC wake-up if SYSTEM_SUSPEND cuts power Geert Uytterhoeven <geert@linux-m68k.org> - 2017-02-21 18:40 +0100
          Re: [PATCH/RFC 0/6] PSCI: Fix non-PMIC wake-up if SYSTEM_SUSPEND cuts  power Sudeep Holla <sudeep.holla@arm.com> - 2017-02-21 19:00 +0100
            Re: [PATCH/RFC 0/6] PSCI: Fix non-PMIC wake-up if SYSTEM_SUSPEND cuts  power Sudeep Holla <sudeep.holla@arm.com> - 2017-02-21 19:40 +0100
              Re: [PATCH/RFC 0/6] PSCI: Fix non-PMIC wake-up if SYSTEM_SUSPEND cuts  power Sudeep Holla <sudeep.holla@arm.com> - 2017-02-21 19:50 +0100
                Re: [PATCH/RFC 0/6] PSCI: Fix non-PMIC wake-up if SYSTEM_SUSPEND cuts power "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2017-02-22 02:30 +0100
                Re: [PATCH/RFC 0/6] PSCI: Fix non-PMIC wake-up if SYSTEM_SUSPEND cuts  power Sudeep Holla <sudeep.holla@arm.com> - 2017-02-22 12:10 +0100
                Re: [PATCH/RFC 0/6] PSCI: Fix non-PMIC wake-up if SYSTEM_SUSPEND cuts power Geert Uytterhoeven <geert@linux-m68k.org> - 2017-02-22 14:40 +0100
                Re: [PATCH/RFC 0/6] PSCI: Fix non-PMIC wake-up if SYSTEM_SUSPEND cuts  power Sudeep Holla <sudeep.holla@arm.com> - 2017-02-22 15:40 +0100
                Re: [PATCH/RFC 0/6] PSCI: Fix non-PMIC wake-up if SYSTEM_SUSPEND cuts power "Rafael J. Wysocki" <rafael@kernel.org> - 2017-02-22 16:00 +0100
                Re: [PATCH/RFC 0/6] PSCI: Fix non-PMIC wake-up if SYSTEM_SUSPEND cuts  power Sudeep Holla <sudeep.holla@arm.com> - 2017-02-22 17:00 +0100
                Re: [PATCH/RFC 0/6] PSCI: Fix non-PMIC wake-up if SYSTEM_SUSPEND cuts power Geert Uytterhoeven <geert@linux-m68k.org> - 2017-02-23 16:30 +0100
                Re: [PATCH/RFC 0/6] PSCI: Fix non-PMIC wake-up if SYSTEM_SUSPEND cuts power Geert Uytterhoeven <geert@linux-m68k.org> - 2017-02-23 16:40 +0100
                Re: [PATCH/RFC 0/6] PSCI: Fix non-PMIC wake-up if SYSTEM_SUSPEND cuts  power Sudeep Holla <sudeep.holla@arm.com> - 2017-02-23 17:00 +0100
                Re: [PATCH/RFC 0/6] PSCI: Fix non-PMIC wake-up if SYSTEM_SUSPEND cuts  power Sudeep Holla <sudeep.holla@arm.com> - 2017-02-23 17:00 +0100
                Re: [PATCH/RFC 0/6] PSCI: Fix non-PMIC wake-up if SYSTEM_SUSPEND cuts power Geert Uytterhoeven <geert@linux-m68k.org> - 2017-02-22 14:20 +0100
                Re: [PATCH/RFC 0/6] PSCI: Fix non-PMIC wake-up if SYSTEM_SUSPEND cuts power "Rafael J. Wysocki" <rafael@kernel.org> - 2017-02-22 15:40 +0100

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