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

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Message-ID: <016dd5fc-08c2-0084-5332-2992ab95f134@arm.com>
Date:   Tue, 21 Feb 2017 16:51:48 +0000
From:   Sudeep Holla <sudeep.holla@....com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Sudeep Holla <sudeep.holla@....com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        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>,
        Magnus Damm <magnus.damm@...il.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Linux PM list <linux-pm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH/RFC 3/6] drivers: firmware: psci: Implement shallow
 suspend mode



On 21/02/17 16:23, Geert Uytterhoeven wrote:
> Hi Sudeep,
> 
> On Tue, Feb 21, 2017 at 11:42 AM, Sudeep Holla <sudeep.holla@....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.
> 

In short or just to summarize in one line, just use "freeze"(a.k.a
suspend-to-idle suspend mode)

-- 
Regards,
Sudeep