linux-kernel - Re: [PATCH V3 04/15] cpufreq: mediatek: Record previous target vproc value

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Date:   Fri, 15 Apr 2022 14:24:19 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Rex-BC Chen <rex-bc.chen@...iatek.com>, rafael@...nel.org,
        viresh.kumar@...aro.org, robh+dt@...nel.org, krzk+dt@...nel.org,
        matthias.bgg@...il.com
Cc:     jia-wei.chang@...iatek.com, roger.lu@...iatek.com,
        hsinyi@...gle.com, khilman@...libre.com, linux-pm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org,
        Project_Global_Chrome_Upstream_Group@...iatek.com,
        "Andrew-sh . Cheng" <andrew-sh.cheng@...iatek.com>
Subject: Re: [PATCH V3 04/15] cpufreq: mediatek: Record previous target vproc
 value

Il 15/04/22 07:59, Rex-BC Chen ha scritto:
> From: Jia-Wei Chang <jia-wei.chang@...iatek.com>
> 
> We found the buck voltage may not be exactly the same with what we set
> because CPU may share the same buck with other module.
> Therefore, we need to record the previous desired value instead of reading
> it from regulators.
> 
> Signed-off-by: Andrew-sh.Cheng <andrew-sh.cheng@...iatek.com>
> Signed-off-by: Jia-Wei Chang <jia-wei.chang@...iatek.com>
> Signed-off-by: Rex-BC Chen <rex-bc.chen@...iatek.com>
> ---
>   drivers/cpufreq/mediatek-cpufreq.c | 17 +++++++++++++----
>   1 file changed, 13 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/cpufreq/mediatek-cpufreq.c b/drivers/cpufreq/mediatek-cpufreq.c
> index ff27f77e8ee6..fa8b193bf27b 100644
> --- a/drivers/cpufreq/mediatek-cpufreq.c
> +++ b/drivers/cpufreq/mediatek-cpufreq.c
> @@ -40,6 +40,7 @@ struct mtk_cpu_dvfs_info {
>   	struct list_head list_head;
>   	int intermediate_voltage;
>   	bool need_voltage_tracking;
> +	int pre_vproc;
>   };
>   
>   static LIST_HEAD(dvfs_info_list);
> @@ -191,11 +192,17 @@ static int mtk_cpufreq_voltage_tracking(struct mtk_cpu_dvfs_info *info,
>   
>   static int mtk_cpufreq_set_voltage(struct mtk_cpu_dvfs_info *info, int vproc)
>   {
> +	int ret;
> +
>   	if (info->need_voltage_tracking)
> -		return mtk_cpufreq_voltage_tracking(info, vproc);
> +		ret = mtk_cpufreq_voltage_tracking(info, vproc);
>   	else
> -		return regulator_set_voltage(info->proc_reg, vproc,
> -					     vproc + VOLT_TOL);
> +		ret = regulator_set_voltage(info->proc_reg, vproc,
> +					    MAX_VOLT_LIMIT);
> +	if (!ret)
> +		info->pre_vproc = vproc;
> +
> +	return ret;
>   }
>   
>   static int mtk_cpufreq_set_target(struct cpufreq_policy *policy,
> @@ -213,7 +220,9 @@ static int mtk_cpufreq_set_target(struct cpufreq_policy *policy,
>   	inter_vproc = info->intermediate_voltage;
>   
>   	pre_freq_hz = clk_get_rate(cpu_clk);
> -	pre_vproc = regulator_get_voltage(info->proc_reg);
> +	pre_vproc = info->pre_vproc;
> +	if (pre_vproc <= 0)
> +		pre_vproc = regulator_get_voltage(info->proc_reg);

I would do it like that, instead:

	if (unlikely(info->pre_vproc <= 0))
		pre_vproc = regulator_get_voltage(info->proc_reg);
	else
		pre_vproc = info->pre_vproc;

....as even though it is indeed possible that info->pre_vproc is <= 0, it is
very unlikely to happen ;-)
This also solves a 'pre_vproc' double assignment issue, by the way.

Cheers,
Angelo