Re: [RFC PATCH 3/3] cpuidle: psci: Initialize the PM domains in powered off state for OSI

On 26-08-19 17:14:53, Ulf Hansson wrote:

From: Ulf Hansson <ulfh@kernel.org>

At the point when the PM domain and the topology are registered through the
genpd subsystem, it's not really known whether corresponding CPUs are
online and thus if the PM domain should be initialized as powered on or
not. Instead this information becomes available when the CPU devices gets
attached to their respective PM domain through dt_idle_attach_cpu().

This is a problem when using PSCI OS-initiated mode, as we may end up with
a PM domain that has the genpd's status indicating it to be powered on,
while it in fact may not be the case. In the less severe scenario, this
leads to selecting a shallower domain idle state for the PM domain than
necessary. A more critical problem is when a non-CPU device shares the PM
domain, leading to their corresponding drivers not being able to trust the
status of it.

Exactly why a third state like GENPD_STATE_UNKNOWN would be more
fitting, IMO. Maybe something we can do at some point.

This solution works for now as well.

Let's fix these problems by initializing the state for the genpd's to be
powered off and in the deepest possible domain idle state, when using
OS-initiated mode. The support for ->sync_state() is maintained by setting
the GENPD_FLAG_OFF_STAY_ON for the genpds in question.

Reported-by: Maulik Shah <redacted>
Link: https://lore.kernel.org/all/20260811-domain_off_ss3-v1-0-6a0a0fc023f5@oss.qualcomm.com/ (local)
Signed-off-by: Ulf Hansson <ulfh@kernel.org>

Reviewed-by: Abel Vesa <redacted>