linux-kernel - Re: [PATCH v1 6/6] cpuidle: tegra: Remove CPUIDLE_FLAG_TIMER

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Date:   Tue, 9 Jul 2019 08:49:37 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Peter De Schrijver <pdeschrijver@...dia.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     linux-pm@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 6/6] cpuidle: tegra: Remove CPUIDLE_FLAG_TIMER_STOP
 from all states

08.07.2019 2:38, Dmitry Osipenko пишет:
> The Tegra's clocksource driver got some rework recently and now the
> internal/local CPU timers usage is discouraged on Tegra20/30 SoCs in
> a favor of the platform-specific timers that are assigned as per-CPU
> clocksources because they do not suffer from the CPU-freq changes and
> are always-ON during of CPU-idling. That happened in the commit
> f6d50ec5f85c ("clocksource/drivers/tegra: Support per-CPU timers on all
> Tegra's"). The Tegra's clocksource driver is the essential arch-driver
> that is guaranteed to always present on all Tegra SoCs up to Tegra124.
> 
> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> ---
>  drivers/cpuidle/cpuidle-tegra.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/drivers/cpuidle/cpuidle-tegra.c b/drivers/cpuidle/cpuidle-tegra.c
> index 464b2376905a..e2aa46231c05 100644
> --- a/drivers/cpuidle/cpuidle-tegra.c
> +++ b/drivers/cpuidle/cpuidle-tegra.c
> @@ -143,7 +143,6 @@ static struct cpuidle_driver tegra_idle_driver = {
>  			.exit_latency		= 2000,
>  			.target_residency	= 2200,
>  			.power_usage		= 0,
> -			.flags			= CPUIDLE_FLAG_TIMER_STOP,
>  			.name			= "powered-down",
>  			.desc			= "CPU core powered-off",
>  		},
> @@ -152,8 +151,7 @@ static struct cpuidle_driver tegra_idle_driver = {
>  			.exit_latency		= 5000,
>  			.target_residency	= 10000,
>  			.power_usage		= 0,
> -			.flags			= CPUIDLE_FLAG_COUPLED |
> -						  CPUIDLE_FLAG_TIMER_STOP,
> +			.flags			= CPUIDLE_FLAG_COUPLED,
>  			.name			= "powered-down",
>  			.desc			= "CPU cluster powered-off",
>  		},
> 

Actually, it should be fine to keep this flag because I found that
tick_broadcast_oneshot_control() checks for the C3STOP flag and thus
CPUIDLE_FLAG_TIMER_STOP has no effect in that case. Will drop this patch in the next revision.