linux-kernel - Re: [RFC PATCH 1/3] cpufreq: fix the return value in 'cpufreq_boost_set

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Date:   Thu, 14 May 2020 15:54:47 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Xiongfeng Wang <wangxiongfeng2@...wei.com>
Cc:     viresh.kumar@...aro.org, Souvik.Chakravarty@....com,
        Thanu.Rangarajan@....com, Sudeep.Holla@....com,
        guohanjun@...wei.com, john.garry@...wei.com,
        jonathan.cameron@...wei.com, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 1/3] cpufreq: fix the return value in 'cpufreq_boost_set_sw()'

On Friday, May 8, 2020 11:11:02 AM CEST Xiongfeng Wang wrote:
> When I try to add SW BOOST support for CPPC, I got the following error:
> cpufreq: cpufreq_boost_trigger_state: Cannot enable BOOST
> cpufreq: store_boost: Cannot enable BOOST!
> 
> It is because return value 1 of 'freq_qos_update_request()' means the
> effective constraint value has changed, not a error code on failures.
> But for 'cpufreq_driver.set_boost()', a nonzero return value means
> failure. So change 'ret' to zero when 'freq_qos_update_request()'
> returns a positive value.
> 
> Signed-off-by: Xiongfeng Wang <wangxiongfeng2@...wei.com>
> ---
>  drivers/cpufreq/cpufreq.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 4adac3a..475fb1b 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -2522,6 +2522,8 @@ static int cpufreq_boost_set_sw(int state)
>  		ret = freq_qos_update_request(policy->max_freq_req, policy->max);
>  		if (ret < 0)
>  			break;
> +		else
> +			ret = 0;
>  	}
>  
>  	return ret;
>

I would change cpufreq_boost_trigger_state() to take the 1 into account properly
instead.

Thanks!