Re: [PATCH v5 1/3] cpuidle: psci: Call cpu_cluster_pm_enter() on the last CPU

Marc Zyngier
2022-02-16T14:39:34Z

On 2022-02-16 13:28, Shawn Guo wrote:
> Make a call to cpu_cluster_pm_enter() on the last CPU going to low
> power
> state (and cpu_cluster_pm_exit() on the firt CPU coming back), so that
> platforms can be notified to set up hardware for getting into the
> cluster
> low power state.
>
> Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
> ---
> drivers/cpuidle/cpuidle-psci.c | 13 +++++++++++++
> 1 file changed, 13 insertions(+)
>
> diff --git a/drivers/cpuidle/cpuidle-psci.c
> b/drivers/cpuidle/cpuidle-psci.c
> index b51b5df08450..c748c1a7d7b1 100644
> --- a/drivers/cpuidle/cpuidle-psci.c
> +++ b/drivers/cpuidle/cpuidle-psci.c
> @@ -37,6 +37,7 @@ struct psci_cpuidle_data {
> static DEFINE_PER_CPU_READ_MOSTLY(struct psci_cpuidle_data,
> psci_cpuidle_data);
> static DEFINE_PER_CPU(u32, domain_state);
> static bool psci_cpuidle_use_cpuhp;
> +static atomic_t cpus_in_idle;
>
> void psci_set_domain_state(u32 state)
> {
> @@ -67,6 +68,14 @@ static int __psci_enter_domain_idle_state(struct
> cpuidle_device *dev,
> if (ret)
> return -1;
>
> + if (atomic_inc_return(&cpus_in_idle) == num_online_cpus()) {
> + ret = cpu_cluster_pm_enter();
> + if (ret) {
> + ret = -1;
> + goto dec_atomic;
> + }
> + }
> +
> /* Do runtime PM to manage a hierarchical CPU toplogy. */
> rcu_irq_enter_irqson();
> if (s2idle)
> @@ -88,6 +97,10 @@ static int __psci_enter_domain_idle_state(struct
> cpuidle_device *dev,
> pm_runtime_get_sync(pd_dev);
> rcu_irq_exit_irqson();
>
> + if (atomic_read(&cpus_in_idle) == num_online_cpus())
> + cpu_cluster_pm_exit();
> +dec_atomic:
> + atomic_dec(&cpus_in_idle);
> cpu_pm_exit();
>
> /* Clear the domain state to start fresh when back from idle. */

Is it just me, or does anyone else find it a bit odd that a cpuidle
driver
calls back into the core cpuidle code to generate new events?

Also, why is this PSCI specific? I would assume that the core cpuidle
code
should be responsible for these transitions, not a random cpuidle
driver.

Thanks,

M.
--
Jazz is not dead. It just smells funny...