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

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Date:   Tue, 21 Feb 2017 10:42:45 +0000
From:   Sudeep Holla <sudeep.holla@....com>
To:     Geert Uytterhoeven <geert+renesas@...der.be>
Cc:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Mark Rutland <mark.rutland@....com>,
        Lina Iyer <lina.iyer@...aro.org>,
        John Stultz <john.stultz@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        Rob Herring <robh+dt@...nel.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Magnus Damm <magnus.damm@...il.com>,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-renesas-soc@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH/RFC 3/6] drivers: firmware: psci: Implement shallow
 suspend mode

Hi Geert,

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

-- 
Regards,
Sudeep