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

From: sudeep.holla@arm.com (Sudeep Holla)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH/RFC 0/6] PSCI: Fix non-PMIC wake-up if SYSTEM_SUSPEND cuts power
Date: Thu, 23 Feb 2017 15:58:31 +0000	[thread overview]
Message-ID: <aaf6b786-3c7e-7323-57b7-db7fc6dc8b3f@arm.com> (raw)
In-Reply-To: <CAMuHMdX3_Vjw2NNTE1XnQkuKS=7YDA4eccEFO1pAZkjw_4q9cg@mail.gmail.com>

Hi Geert,

On 23/02/17 15:34, Geert Uytterhoeven wrote:
> Hi Sudeep,
> 
> On Thu, Feb 23, 2017 at 4:26 PM, Geert Uytterhoeven
> <geert@linux-m68k.org> wrote:
>> On Wed, Feb 22, 2017 at 3:32 PM, Sudeep Holla <sudeep.holla@arm.com> wrote:
>>> On 22/02/17 13:38, Geert Uytterhoeven wrote:
>>>> On Wed, Feb 22, 2017 at 12:03 PM, Sudeep Holla <sudeep.holla@arm.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.
> 

Then stop caring about extra power usage too ;). Seriously this is not a
valid argument.

>>>> 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.
> 

Again when you have both "deep" and "standby" suspend states as per your
patch set, user has to choose one. No escape from that.

-- 
Regards,
Sudeep