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    SubjectRe: [PATCH/RFC 3/6] drivers: firmware: psci: Implement shallow suspend mode
    Hi Sudeep,

    On Tue, Feb 21, 2017 at 11:42 AM, Sudeep Holla <sudeep.holla@arm.com> wrote:
    > On 20/02/17 20:33, Geert Uytterhoeven 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.
    >>
    >> List the available system suspend modes:
    >>
    >> $ cat /sys/power/mem_sleep
    >> s2idle shallow [deep]
    >>
    >> Suspend to "shallow" mode:
    >>
    >> $ echo shallow > /sys/power/mem_sleep
    >> $ echo mem > /sys/power/state
    >>
    >
    > I don't have the links to such previous attempts handy, but we have

    Don't worry, I did read earlier discussions about implementing shallow mode.

    > more elegant alternative options(suspend-to-idle) and any such attempts
    > to hack around the PSCI will be NACKed.

    "s2idle" does not power down secondary CPU cores, so this is an improvement.
    "deep" may not support configured wake-up sources, which is a bug.

    Gr{oetje,eeting}s,

    Geert

    --
    Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

    In personal conversations with technical people, I call myself a hacker. But
    when I'm talking to journalists I just say "programmer" or something like that.
    -- Linus Torvalds

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