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

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Message-ID: <3c8b3f2d-8604-f999-4208-a82f171b64f2@arm.com>
Date:   Tue, 21 Feb 2017 18:45:13 +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 18:27, Sudeep Holla wrote:
> 
> 
> 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. 

I take this back, you have everything you need in place, nothing needs
to be done. I just checked again. If I don't register PSCI suspend_ops,
I still get mem in /sys/power/state with s2idle in /sys/power/mem_sleep
which is exactly what we need. Again we don't support standby/shallow
state on ARM64/PSCI.

-- 
Regards,
Sudeep