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

From: Geert Uytterhoeven
Date: Thu Feb 23 2017 - 10:34:58 EST

Hi Sudeep,

On Thu, Feb 23, 2017 at 4:26 PM, Geert Uytterhoeven
<geert@xxxxxxxxxxxxxx> wrote:
> On Wed, Feb 22, 2017 at 3:32 PM, Sudeep Holla <sudeep.holla@xxxxxxx> wrote:
>> On 22/02/17 13:38, Geert Uytterhoeven wrote:
>>> On Wed, Feb 22, 2017 at 12:03 PM, Sudeep Holla <sudeep.holla@xxxxxxx> 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.



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

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