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

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Date: Mon, 29 Apr 2024 13:59:51 -0700 (PDT)
From: Palmer Dabbelt <palmer@...belt.com>
To: ulf.hansson@...aro.org
CC: nick.hu@...ive.com, anup@...infault.org, rafael@...nel.org,
  daniel.lezcano@...aro.org, Paul Walmsley <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, 29 Apr 2024 07:32:12 PDT (-0700), ulf.hansson@...aro.org wrote:
> 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.

Sorry about that, I'll toss it.  I'm testing some other stuff right now 
so it might miss today's linux-next.

>> ---
>>  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