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

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Date:   Thu, 23 Feb 2017 16:34:50 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        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>,
        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

Hi Sudeep,

On Thu, Feb 23, 2017 at 4:26 PM, Geert Uytterhoeven
<geert@...ux-m68k.org> wrote:
> On Wed, Feb 22, 2017 at 3:32 PM, Sudeep Holla <sudeep.holla@....com> wrote:
>> On 22/02/17 13:38, Geert Uytterhoeven wrote:
>>> On Wed, Feb 22, 2017 at 12:03 PM, Sudeep Holla <sudeep.holla@....com> wrote:
>>>   4. Patch 3/6 adds a new "shallow" state, as it allows to save more
>>> power (the difference may be due to suboptimal cpuidle platform support on R-Car Gen3, though),
>>
>> Why can't you do that in s2idle mode. Please give me the difference
>> between your shallow state and s2idle state, not just power numbers
>> but the actual state of CPUs and the devices in the system.
>
> From the Linux side, there's not much difference, except that the secondary
> CPU cores are disabled.  As that is handled by PSCI, the difference may be
> in the PSCI implementation.  I will have to check that...
>
> On these SoCs, the individual CPU cores and the SCU/L2 are in separate
> (nested) power areas.  Perhaps these power areas are turned off when
> disabling the CPU cores, but not when suspending them.

BTW, I don't care much about the extra state.

>>> E.g. on non-PSCI platforms with an Ethernet driver that supports
>>> Wake-on-LAN, I can do:
>>>
>>>         ethtool -s eth0 wol g
>>>         echo mem > /sys/power/state
>>>
>>> and be sure that the system can be woken up by sending a WoL MagicPacket.
>>
>> Still possible with s2idle if CPU_SUSPEND is correctly implemented by
>> the platform.
>
> Sure. But not automatic, as it needs fiddling with mem_sleep.

I do care about this, as it affects user experience.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds