linux-kernel - Re: [PATCH V2 10/15] cpufreq: mediatek: Make sram regulator optional

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Date:   Thu, 14 Apr 2022 18:53:39 +0800
From:   Rex-BC Chen <rex-bc.chen@...iatek.com>
To:     Kevin Hilman <khilman@...libre.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 10/15] cpufreq: mediatek: Make sram regulator optional

On Fri, 2022-04-08 at 13:32 -0700, Kevin Hilman wrote:
> Rex-BC Chen <rex-bc.chen@...iatek.com> writes:
> 
> > From: Jia-Wei Chang <jia-wei.chang@...iatek.com>
> > 
> > For some MediaTek SoCs, like MT8186, it's possible that the sram
> > regulator
> > is shared between CPU and CCI.
> > 
> > Signed-off-by: Jia-Wei Chang <jia-wei.chang@...iatek.com>
> 
> nit: missing your sign-off.
> 
> > ---
> >  drivers/cpufreq/mediatek-cpufreq.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/cpufreq/mediatek-cpufreq.c
> > b/drivers/cpufreq/mediatek-cpufreq.c
> > index 9e9bce0ff235..8f688d47e64b 100644
> > --- a/drivers/cpufreq/mediatek-cpufreq.c
> > +++ b/drivers/cpufreq/mediatek-cpufreq.c
> > @@ -435,7 +435,7 @@ static int mtk_cpu_dvfs_info_init(struct
> > mtk_cpu_dvfs_info *info, int cpu)
> >  	}
> >  
> >  	/* Both presence and absence of sram regulator are valid cases.
> > */
> > -	info->sram_reg = regulator_get_exclusive(cpu_dev, "sram");
> > +	info->sram_reg = regulator_get_optional(cpu_dev, "sram");
> 
> The changelog says that this regulator may be shared with CCI, so I
> understand it's no longer exclusive.  But here you make it optional,
> which should be explained in the changelog.  If it's not actually
> optional, then it should just be normal "get".
> 
> Kevin

Hello Kevin,

Since cpufreq and cci devfreq might share the same sram regulator in
MediaTek SoC, it is no longer exclusive as you mentioned.

The reason to use regulator_get_optional is we hope regulator framework
can return error for error handling rather than a dummy handler from
regulator_get api.

I will add this to commit message in next version.

Thanks.

BRs,
Rex