Re: [PATCH v2 1/2] cpuidle: psci: Move enabling OSI mode after power domains creation

[Sudeep Holla]

On Thu, Mar 30, 2023 at 02:12:49PM +0530, Maulik Shah wrote:
> A switch from OSI to PC mode is only possible if all CPUs other than the
> calling one are OFF, either through a call to CPU_OFF or not yet booted.
>

As per the spec, all cores are in one of the following states:
 - Running
 - OFF, either through a call to CPU_OFF or not yet booted
 - Suspended, through a call to CPU_DEFAULT_SUSPEND

Better to provide full information.

> Currently OSI mode is enabled before power domains are created. In cases
> where CPUidle states are not using hierarchical CPU topology the bail out
> path tries to switch back to PC mode which gets denied by firmware since
> other CPUs are online at this point and creates inconsistent state as
> firmware is in OSI mode and Linux in PC mode.
>

OK what is the issue if the other cores are online ? As long as they are
running, it is allowed in the spec, so your statement is incorrect.

Is CPUidle enabled before setting the OSI mode. I see only that can cause
issue as we don't use CPU_DEFAULT_SUSPEND. If idle is not yet enabled, it
shouldn't be a problem.

-- 
Regards,
Sudeep