Re: [PATCH 6/6] PSCI: cpuidle: Refactor CPU suspend power_state parameter handling

[Ulf Hansson <ulf.hansson@linaro.org>]

On Thu, 8 Aug 2019 at 14:55, Sudeep Holla <sudeep.holla@arm.com> wrote:
>
> On Mon, Jul 22, 2019 at 04:37:45PM +0100, Lorenzo Pieralisi wrote:
> > Current PSCI code handles idle state entry through the
> > psci_cpu_suspend_enter() API, that takes an idle state index as a
> > parameter and convert the index into a previously initialized
> > power_state parameter before calling the PSCI.CPU_SUSPEND() with it.
> >
> > This is unwieldly, since it forces the PSCI firmware layer to keep track
> > of power_state parameter for every idle state so that the
> > index->power_state conversion can be made in the PSCI firmware layer
> > instead of the CPUidle driver implementations.
> >
> > Move the power_state handling out of drivers/firmware/psci
> > into the respective ACPI/DT PSCI CPUidle backends and convert
> > the psci_cpu_suspend_enter() API to get the power_state
> > parameter as input, which makes it closer to its firmware
> > interface PSCI.CPU_SUSPEND() API.
> >
> > A notable side effect is that the PSCI ACPI/DT CPUidle backends
> > now can directly handle (and if needed update) power_state
> > parameters before handing them over to the PSCI firmware
> > interface to trigger PSCI.CPU_SUSPEND() calls.
> >
> > Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> > Cc: Will Deacon <will@kernel.org>
> > Cc: Ulf Hansson <ulf.hansson@linaro.org>
> > Cc: Sudeep Holla <sudeep.holla@arm.com>
>
> Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
>
> > +static __init int psci_cpu_init_idle(unsigned int cpu)
> > +{
> > +     struct device_node *cpu_node;
> > +     int ret;
> > +
> > +     /*
> > +      * If the PSCI cpu_suspend function hook has not been initialized
> > +      * idle states must not be enabled, so bail out
> > +      */
> > +     if (!psci_ops.cpu_suspend)
> > +             return -EOPNOTSUPP;
> > +
> > +     cpu_node = of_get_cpu_node(cpu, NULL);
>
> [nit] You could use of_cpu_device_node_get in linux/of_device.h as
> it may avoid parsing if used later during the boot(i.e. after
> cpu->of_node is populated). I think there's another instance in
> psci_idle_init_cpu

Good idea!

However, as $subject patch more or less just moves code from the
current psci firmware directory into cpuidle, perhaps it's better to
defer improvements to be made on top?

Kind regards
Uffe