From mboxrd@z Thu Jan  1 00:00:00 1970
From: Sudeep Holla <sudeep.holla@arm.com>
Subject: Re: [PATCH/RFC 3/6] drivers: firmware: psci: Implement shallow
 suspend mode
Date: Tue, 21 Feb 2017 16:51:48 +0000
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To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Sudeep Holla <sudeep.holla@arm.com>, Geert Uytterhoeven <geert+renesas@glider.be>, Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>, Mark Rutland <mark.rutland@arm.com>, Lina Iyer <lina.iyer@linaro.org>, John Stultz <john.stultz@linaro.org>, Thomas Gleixner <tglx@linutronix.de>, "Rafael J . Wysocki" <rjw@rjwysocki.net>, Len Brown <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>, Rob Herring <robh+dt@kernel.org>, Magnus Damm <magnus.damm@gmail.com>, "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>, "linux-arm-kernel@lists.infradead.org" <linux-arm-kernel@lists.infradead.org>, Linux-Renesas <linux-renesas-soc@vger.kernel.org>, Linux PM list <linux-pm@vger.kernel.org>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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On 21/02/17 16:23, Geert Uytterhoeven wrote:
> 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.
> 

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

-- 
Regards,
Sudeep