linux-kernel - Re: [PATCH v2 3/4] sched: idle: Respect the CPU system-wakeup QoS limit for s2idle

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Message-ID: <20251017101515.GX4067720@noisy.programming.kicks-ass.net>
Date: Fri, 17 Oct 2025 12:15:15 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Ulf Hansson <ulf.hansson@...aro.org>
Cc: "Rafael J . Wysocki" <rafael@...nel.org>, linux-pm@...r.kernel.org,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Kevin Hilman <khilman@...libre.com>,
	Pavel Machek <pavel@...nel.org>, Len Brown <len.brown@...el.com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Saravana Kannan <saravanak@...gle.com>,
	Maulik Shah <quic_mkshah@...cinc.com>,
	Prasad Sodagudi <psodagud@...cinc.com>, Dhruva Gole <d-gole@...com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/4] sched: idle: Respect the CPU system-wakeup QoS
 limit for s2idle

On Thu, Oct 16, 2025 at 05:19:23PM +0200, Ulf Hansson wrote:

No objections to this.

Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>

> diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
> index c39b089d4f09..c1c3d0166610 100644
> --- a/kernel/sched/idle.c
> +++ b/kernel/sched/idle.c
> @@ -131,12 +131,13 @@ void __cpuidle default_idle_call(void)
>  }
>  
>  static int call_cpuidle_s2idle(struct cpuidle_driver *drv,
> -			       struct cpuidle_device *dev)
> +			       struct cpuidle_device *dev,
> +			       u64 max_latency_ns)
>  {
>  	if (current_clr_polling_and_test())
>  		return -EBUSY;
>  
> -	return cpuidle_enter_s2idle(drv, dev);
> +	return cpuidle_enter_s2idle(drv, dev, max_latency_ns);
>  }
>  
>  static int call_cpuidle(struct cpuidle_driver *drv, struct cpuidle_device *dev,
> @@ -205,12 +206,13 @@ static void cpuidle_idle_call(void)
>  		u64 max_latency_ns;
>  
>  		if (idle_should_enter_s2idle()) {
> +			max_latency_ns = cpu_wakeup_latency_qos_limit() *
> +					 NSEC_PER_USEC;
>  
> -			entered_state = call_cpuidle_s2idle(drv, dev);
> +			entered_state = call_cpuidle_s2idle(drv, dev,
> +							    max_latency_ns);
>  			if (entered_state > 0)
>  				goto exit_idle;
> -
> -			max_latency_ns = U64_MAX;
>  		} else {
>  			max_latency_ns = dev->forced_idle_latency_limit_ns;
>  		}
> -- 
> 2.43.0
>