linux-kernel - Re: [PATCH/RFC 0/6] PSCI: Fix non-PMIC wake-up if SYSTEM

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Message-ID: <94167d3a-e005-3af0-d290-a1086684d570@arm.com>
Date:   Tue, 21 Feb 2017 18:27:59 +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 0/6] PSCI: Fix non-PMIC wake-up if SYSTEM_SUSPEND cuts
 power

On 21/02/17 17:51, Sudeep Holla wrote:
> 
> 
> On 21/02/17 17:34, Geert Uytterhoeven wrote:

[...]

>>
>> The SoC can wake-up. It's just not guaranteed that it can wake-up using
>> the wakeup-source configured from Linux. Which wakeup-sources are available
>> depends on the actual PSCI implementation.  It's not specified by the PSCI
>> specification.
>>
>>> Just botching whatever shallow state you can enter on a particular SoC
>>> into standard "mem" state sounds *horrible* to me.
>>
>> That's more or less what /sys/power/mem_sleep does, though.
>>
> 
> OK, I will go through that in detail.
> 

OK, I went through the patch and the main intention is was added.
So I will begin by summarizing my understanding:

A new suspend interface(/sys/power/mem_sleep) is added to allow the
"mem" string in /sys/power/state to represent multiple things that can
be selected.

Before:
A. echo freeze > /sys/power/state ---> Enters s2idle
B. echo mem > /sys/power/state ---> Enters s2r(a.k.a now deep mem sleep)

After:
1. echo freeze > /sys/power/state ---> Enters s2idle still same
2. echo s2idle > /sys/power/mem_sleep
   echo mem > /sys/power/state ---> Also enter s2idle
3. echo deep > /sys/power/mem_sleep
   echo mem > /sys/power/state ---> Also enter s2r(same as [B] above)

Please note I have carefully dropped standby/shallow as we will not
support that state on ARM64 platforms(refer previous discussions for the
same)

Now IIUC, you need 2 above. So, since this new interface allow mem to
mean "s2idle", we need to fix the core to register default suspend_ops
to achieve what you need. And since I now better understand you problem,
you get extra NACK for this series ;)

-- 
Regards,
Sudeep