-----Original Message-----
From: Oliver Neukum [mailto:oneukum at suse.com]
Sent: Tuesday, May 17, 2016 7:54 PM
To: Hongbo Zhang <redacted>
Cc: Sudeep Holla <redacted>; linux-pm at vger.kernel.org;
Lorenzo Pieralisi [off-list ref]; Marc Zyngier
[off-list ref]; Jan Kiszka [off-list ref]; Mark
Rutland [off-list ref]; Daniel Lezcano
[off-list ref]; Chen-Yu Tsai [off-list ref]; Hans de Goede
[off-list ref]; Frank Li [off-list ref]; Peng Fan
[off-list ref]; Tom Warren [off-list ref]; Vincent
Guittot [off-list ref]; jszhang at marvell.com; linux-arm-
kernel at lists.infradead.org
Subject: Re: [PSCI DISCUSS] How to implement standby and suspend-to-ram by
PSCI

On Thu, 2016-05-12 at 09:42 +0000, Hongbo Zhang wrote:

quoted

On our platform we have some shallow states which maps to cpuidle
well,
and we have two more deeper states:

Sleep state:
All cores are in WFI state,
Core cluster is in standby state, e.g. L2 cache is flushed then stops
snooping,
Only those modules which are required to wake up the device still have
a
running clock, other device modules in chip are clock gated.

Deep sleep state:
ARM cores and DDR controller are switched off,
DDR is in self-refresh mode,
VDD power to off domain IPs are removed, Only the blocks needed to
detect wake up and sequence the chip out of deep sleep are on.

For the pm module of the core kernel a low power state is a sleep
state if even one of three conditions is met:

a) a device that can be used for input is not a source of wake ups
b) tasks need to be frozen to enter it
c) the display goes off, while it should be on

Generally runtime PM is better if you can get the same results.
Going to a system sleep state is a necessary evil.

	Regards
		Oliver

As I just explained in previous reply, many devices in our Soc cannot be physically clock or power gated, all the non-wakeup devices can only be gated off at same time by a PM module, so runtime PM doesn't fit for us well.

Thanks for your advice.