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

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Message-ID: <3a1fe42adace3a1355b6a95fbd55abc724c1053d.camel@mediatek.com>
Date:   Mon, 18 Apr 2022 09:37:45 +0800
From:   Rex-BC Chen <rex-bc.chen@...iatek.com>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.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

On Fri, 2022-04-15 at 14:24 +0200, AngeloGioacchino Del Regno wrote:
> 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
> 
> 
> 

Hello Angelo,

OK, I will add this in next version.
Thanks for your suggestion.

BRs,
Rex