linux-kernel - Re: [PATCH V3 11/15] cpufreq: mediatek: Link CCI device to CPU

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <fb61128ab1534982ed9f8c8d7a141afad04d8fbb.camel@mediatek.com>
Date:   Mon, 18 Apr 2022 09:45:09 +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>
Subject: Re: [PATCH V3 11/15] cpufreq: mediatek: Link CCI device to CPU

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>
> > 
> > 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.
> > 
> > Before CCI devfreq is ready, we record the voltage when booting to
> > kernel and use the max(cpu target voltage, booting voltage) to
> > prevent cpufreq adjust to the lower voltage which will cause the
> > CCI
> > crash because of high frequency and low voltage.
> > 
> > - 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>
> > Signed-off-by: Rex-BC Chen <rex-bc.chen@...iatek.com>
> 
> I am enthusiast to see that the solution that I've proposed was
> welcome!
> 
> I only have one nit on this patch, check below:
> 

Hello Angelo,

Thanks for your advice for this modification.
I also reply to Kevin and describe this solution.
Let's wait for Kevin's feedback and other suggestion.

> > ---
> >   drivers/cpufreq/mediatek-cpufreq.c | 80
> > +++++++++++++++++++++++++++++-
> >   1 file changed, 79 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/cpufreq/mediatek-cpufreq.c
> > b/drivers/cpufreq/mediatek-cpufreq.c
> > index d4c00237e862..dd3f739fede1 100644
> > --- a/drivers/cpufreq/mediatek-cpufreq.c
> > +++ b/drivers/cpufreq/mediatek-cpufreq.c
> 
> ..snip..
> 
> > @@ -225,6 +251,14 @@ static int mtk_cpufreq_set_target(struct
> > cpufreq_policy *policy,
> >   	vproc = dev_pm_opp_get_voltage(opp);
> >   	dev_pm_opp_put(opp);
> >   
> > +	/*
> > +	 * If MediaTek cci is supported but is not ready, we will use
> > the value
> > +	 * of max(target cpu voltage, booting voltage) to prevent high
> > freqeuncy
> > +	 * low voltage crash.
> > +	 */
> > +	if (info->soc_data->ccifreq_supported &&
> > !is_ccifreq_ready(info))
> > +		vproc = max(vproc, info->vproc_on_boot);
> > +
> >   	/*
> >   	 * If the new voltage or the intermediate voltage is higher
> > than the
> >   	 * current voltage, scale up voltage first.
> 
> ..snip..
> 
> > @@ -423,6 +484,13 @@ static int mtk_cpu_dvfs_info_init(struct
> > mtk_cpu_dvfs_info *info, int cpu)
> >   	if (ret)
> >   		goto out_disable_mux_clock;
> >   
> > +	info->vproc_on_boot = regulator_get_voltage(info->proc_reg);
> 
> This result is used only if we use ccifreq, so this should be
> enclosed in an if
> condition: this will spare us some (yes, small) time on devices that
> don't use it.
> 
> 	if (info->soc_data->ccifreq_supported) {
> 		info->vproc_on_boot = regulator_get_voltage(info-
> >proc_reg);
> 		if (info->vproc_on_boot < 0) {
> 			dev_err(....
> 			goto ..
> 		}
> 	}
> 
> P.S.: While at it, since the maximum width is 100 columns, the
> dev_err() call fits,
> so don't break that line!
> 
> After the requested change:
> 
> Reviewed-by: AngeloGioacchino Del Regno <
> angelogioacchino.delregno@...labora.com>

I will add this in next version if there is no any suggestion for this
patch.

Thanks!

BRs,
Rex