linux-kernel - Re: [PATCH 2/2] cpufreq: arm_scmi: Set fast_switch

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Message-ID: <20200618095429.tj3ddquy5m2q367e@vireshk-i7>
Date:   Thu, 18 Jun 2020 15:24:29 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Nicola Mazzucato <nicola.mazzucato@....com>
Cc:     linux-kernel@...r.kernel.org, sudeep.holla@....com,
        rjw@...ysocki.net, linux-arm-kernel@...ts.infradead.org,
        linux-pm@...r.kernel.org, lukasz.luba@....com
Subject: Re: [PATCH 2/2] cpufreq: arm_scmi: Set fast_switch_possible
 conditionally

On 17-06-20, 10:43, Nicola Mazzucato wrote:
> Currently the fast_switch_possible flag is set unconditionally
> to true. Based on this, schedutil does not create a
> thread for frequency switching and would always use the
> fast switch path.
> However, if the platform does not support frequency
> fast switch, this may cause the governor to attempt an
> operation that is not supported by the platform.
> 
> Fix this by correctly retrieve the fast_switch capability
> from the driver which knows if the platform can support
> this feature.
> 
> Suggested-by: Lukasz Luba <lukasz.luba@....com>
> Signed-off-by: Nicola Mazzucato <nicola.mazzucato@....com>
> ---
>  drivers/cpufreq/scmi-cpufreq.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/cpufreq/scmi-cpufreq.c b/drivers/cpufreq/scmi-cpufreq.c
> index 61623e2ff149..1cf688fcb56b 100644
> --- a/drivers/cpufreq/scmi-cpufreq.c
> +++ b/drivers/cpufreq/scmi-cpufreq.c
> @@ -198,7 +198,8 @@ static int scmi_cpufreq_init(struct cpufreq_policy *policy)
>  
>  	policy->cpuinfo.transition_latency = latency;
>  
> -	policy->fast_switch_possible = true;
> +	policy->fast_switch_possible =
> +		handle->perf_ops->fast_switch_possible(handle, cpu_dev);
>  
>  	em_register_perf_domain(policy->cpus, nr_opp, &em_cb);

Acked-by: Viresh Kumar <viresh.kumar@...aro.org>

-- 
viresh