linux-kernel - Re: [PATCH] cpuidle: riscv-sbi: Add cluster_pm

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Date: Mon, 29 Apr 2024 16:32:12 +0200
From: Ulf Hansson <ulf.hansson@...aro.org>
To: Nick Hu <nick.hu@...ive.com>, palmer@...belt.com
Cc: anup@...infault.org, rafael@...nel.org, daniel.lezcano@...aro.org, 
	paul.walmsley@...ive.com, linux-pm@...r.kernel.org, 
	linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	zong.li@...ive.com
Subject: Re: [PATCH] cpuidle: riscv-sbi: Add cluster_pm_enter()/exit()

On Mon, 26 Feb 2024 at 07:51, Nick Hu <nick.hu@...ive.com> wrote:
>
> When the cpus in the same cluster are all in the idle state, the kernel
> might put the cluster into a deeper low power state. Call the
> cluster_pm_enter() before entering the low power state and call the
> cluster_pm_exit() after the cluster woken up.
>
> Signed-off-by: Nick Hu <nick.hu@...ive.com>

I was not cced this patch, but noticed that this patch got queued up
recently. Sorry for not noticing earlier.

If not too late, can you please drop/revert it? We should really move
away from the CPU cluster notifiers. See more information below.

> ---
>  drivers/cpuidle/cpuidle-riscv-sbi.c | 24 ++++++++++++++++++++++--
>  1 file changed, 22 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/cpuidle/cpuidle-riscv-sbi.c b/drivers/cpuidle/cpuidle-riscv-sbi.c
> index e8094fc92491..298dc76a00cf 100644
> --- a/drivers/cpuidle/cpuidle-riscv-sbi.c
> +++ b/drivers/cpuidle/cpuidle-riscv-sbi.c
> @@ -394,6 +394,7 @@ static int sbi_cpuidle_pd_power_off(struct generic_pm_domain *pd)
>  {
>         struct genpd_power_state *state = &pd->states[pd->state_idx];
>         u32 *pd_state;
> +       int ret;
>
>         if (!state->data)
>                 return 0;
> @@ -401,6 +402,10 @@ static int sbi_cpuidle_pd_power_off(struct generic_pm_domain *pd)
>         if (!sbi_cpuidle_pd_allow_domain_state)
>                 return -EBUSY;
>
> +       ret = cpu_cluster_pm_enter();
> +       if (ret)
> +               return ret;

Rather than using the CPU cluster notifiers, consumers of the genpd
can register themselves to receive genpd on/off notifiers.

In other words, none of this should be needed, right?

[...]

Kind regards
Uffe