linux-kernel - Re: [PATCH V2 13/15] cpufreq: mediatek: Link CCI device to CPU

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Message-ID: <7920cc153930ab1e724fe65df370fc70f6cbe3db.camel@mediatek.com>
Date:   Mon, 11 Apr 2022 19:50:03 +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>
CC:     <matthias.bgg@...il.com>, <jia-wei.chang@...iatek.com>,
        <roger.lu@...iatek.com>, <hsinyi@...gle.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>
Subject: Re: [PATCH V2 13/15] cpufreq: mediatek: Link CCI device to CPU

On Fri, 2022-04-08 at 15:37 +0200, AngeloGioacchino Del Regno wrote:
> Il 08/04/22 06:59, Rex-BC Chen ha scritto:
> > From: Jia-Wei Chang <jia-wei.chang@...iatek.com>
> > 
> > In some MediaTek SoCs, like MT8183, CPU and CCI share the same
> > power
> > supplies. Cpufreq needs to check if CCI devfreq exists and wait
> > until
> > CCI devfreq ready before scaling frequency.
> > 
> > - Add is_ccifreq_ready() to link CCI device to CPI, and CPU will
> > start
> >    DVFS when CCI is ready.
> > - Add platform data for MT8183.
> > 
> > Signed-off-by: Jia-Wei Chang <jia-wei.chang@...iatek.com>
> > ---
> >   drivers/cpufreq/mediatek-cpufreq.c | 69
> > +++++++++++++++++++++++++++++-
> >   1 file changed, 68 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/cpufreq/mediatek-cpufreq.c
> > b/drivers/cpufreq/mediatek-cpufreq.c
> > index b08ab7c14818..cebe5af2ef5d 100644
> > --- a/drivers/cpufreq/mediatek-cpufreq.c
> > +++ b/drivers/cpufreq/mediatek-cpufreq.c
> > @@ -22,6 +22,7 @@ struct mtk_cpufreq_platform_data {
> >   	int proc_max_volt;
> >   	int sram_min_volt;
> >   	int sram_max_volt;
> > +	bool is_ccifreq_support;
> 
> bool ccifreq_supported; looks better.

Hello Angelo,

Thanks for your review.

OK, I will modify this in next version.

> 
> >   };
> >   
> >   /*
> > @@ -38,6 +39,7 @@ struct mtk_cpufreq_platform_data {
> >   struct mtk_cpu_dvfs_info {
> >   	struct cpumask cpus;
> >   	struct device *cpu_dev;
> > +	struct device *cci_dev;
> >   	struct regulator *proc_reg;
> >   	struct regulator *sram_reg;
> >   	struct clk *cpu_clk;
> > @@ -52,6 +54,7 @@ struct mtk_cpu_dvfs_info {
> >   	int opp_cpu;
> >   	unsigned long opp_freq;
> >   	const struct mtk_cpufreq_platform_data *soc_data;
> > +	bool is_ccifreq_bounded;
> 
> bool ccifreq_bound; looks better.
> 

OK, I will modify this in next version.

> >   };
> >   
> >   static struct platform_device *cpufreq_pdev;
> > @@ -171,6 +174,29 @@ static int mtk_cpufreq_set_voltage(struct
> > mtk_cpu_dvfs_info *info, int vproc)
> >   	return ret;
> >   }
> >   
> > +static bool is_ccifreq_ready(struct mtk_cpu_dvfs_info *info)
> > +{
> > +	struct device_link *sup_link;
> > +
> > +	if (info->is_ccifreq_bounded)
> > +		return true;
> > +
> > +	sup_link = device_link_add(info->cpu_dev, info->cci_dev,
> > +				   DL_FLAG_AUTOREMOVE_CONSUMER);
> > +	if (!sup_link) {
> > +		dev_err(info->cpu_dev, "cpu%d: sup_link is NULL\n",
> > +			info->opp_cpu);
> 
> Please, don't break this line: 84 columns are ok.
> 

OK, I will modify this in next version.

> > +		return false;
> > +	}
> > +
> > +	if (sup_link->supplier->links.status != DL_DEV_DRIVER_BOUND)
> > +		return false;
> > +
> > +	info->is_ccifreq_bounded = true;
> > +
> > +	return true;
> > +}
> > +
> >   static int mtk_cpufreq_set_target(struct cpufreq_policy *policy,
> >   				  unsigned int index)
> >   {
> > @@ -183,6 +209,9 @@ static int mtk_cpufreq_set_target(struct
> > cpufreq_policy *policy,
> >   	long freq_hz, old_freq_hz;
> >   	int vproc, old_vproc, inter_vproc, target_vproc, ret;
> >   
> > +	if (info->soc_data->is_ccifreq_support &&
> > !is_ccifreq_ready(info))
> > +		return 0;
> 
> Honestly, I think that pretending that everything is alright and
> faking
> set_target success is *not* a good idea...
> 
> You should return -EAGAIN here, not zero.
> 
> Regards,
> Angelo
> 

As metioneded by Kevin, I will review these three situations.
Thanks for your suggestion.

BRs,
Rex