Re: [PATCH/RFC 0/6] PSCI: Fix non-PMIC wake-up if SYSTEM_SUSPEND cuts power

[Geert Uytterhoeven <geert@linux-m68k.org>]

Hi Rafael,

On Wed, Feb 22, 2017 at 2:14 AM, Rafael J. Wysocki <rjw@rjwysocki.net> wrote:
> On Tuesday, February 21, 2017 06:45:13 PM Sudeep Holla wrote:
>> 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:
>> >>> 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.
>
> Except for one thing which may or may not be a concern here.
>
> Suspend to idle should only go into states in which all of the available wakeup
> devices work.  If there are devices that cannot wake you up from a given state,
> this isn't "idle" any more, is it?

Indeed. And I have no problem with handling wake-up sources from Linux,
as Linux knows how to handle them.

> As for the device wakeup disable/enable interface, it is for controlling
> whether or not a given device should be allowed to generate wakeup signals at
> all.

OK. So it's not guaranteed that it will actually work...

> The information on what states a given device can wake up the system from is
> platform-specific and generally would need to be taken into consideration at
> the platform level.

So that's PSCI on arm64?
But the PSCI specification doesn't handle that.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-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