linux-kernel - Re: [v5, PATCH 4/5] cpufreq: mediatek: add opp notification for SVS support

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Date:   Wed, 11 Mar 2020 11:36:16 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     "andrew-sh.cheng" <andrew-sh.cheng@...iatek.com>
Cc:     Mark Rutland <mark.rutland@....com>, Nishanth Menon <nm@...com>,
        srv_heupstream <srv_heupstream@...iatek.com>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        Stephen Boyd <sboyd@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Fan Chen (陳凡) <fan.chen@...iatek.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [v5, PATCH 4/5] cpufreq: mediatek: add opp notification for SVS
 support

On 10-03-20, 16:11, andrew-sh.cheng wrote:
> On Tue, 2019-12-10 at 14:43 +0800, Viresh Kumar wrote:
> > On 09-12-19, 14:56, andrew-sh.cheng wrote:
> > > On Wed, 2019-11-27 at 14:06 +0530, Viresh Kumar wrote:
> > > > On 26-11-19, 19:50, Andrew-sh.Cheng wrote:
> > > > > +		if (!IS_ERR(opp_item))
> > > > > +			dev_pm_opp_put(opp_item);
> > > > > +		else
> > > > > +			freq = 0;
> > > > > +
> > > > 
> > > > What is the purpose of the above code ?
> > > When dev_pm_opp_find_freq_ceil() doesn't find matching opp item, freq
> > > value won't be set.
> > > Set it as 0 for below checking
> > > > 
> > > > > +		/* case of current opp is disabled */
> > > > > +		if (freq == 0 || freq != info->opp_freq) {
> > > > > +			// find an enable opp item
> > > > > +			freq = 1;
> > > > > +			opp_item = dev_pm_opp_find_freq_ceil(info->cpu_dev,
> > > > > +							     &freq);
> > > > > +			if (!IS_ERR(opp_item)) {
> > > > > +				dev_pm_opp_put(opp_item);
> > > > > +				policy = cpufreq_cpu_get(info->opp_cpu);
> > > > > +				if (policy) {
> > > > > +					cpufreq_driver_target(policy,
> > > > > +						freq / 1000,
> > > > > +						CPUFREQ_RELATION_L);
> > > > 
> > > > Why don't you simply call this instead of all the code in the else
> > > > block ?
> > > These else code is used to check "current opp item is disabled or not".
> > > If not, do nothing.
> > > If current opp item is disabled, need to find an not-disabled opp item,
> > > and set frequency to it.
> > 
> > Right. So this notifier helper of yours receive the opp which is getting
> > disabled, why don't you compare its frequency directly to see if the current OPP
> > is getting disabled ?
> Sorry to overlook your question.
> This is because when the opp is disabled,
> we cannot use dev_pm_opp_get_freq() to get frequency of that opp.
> There is a check:
> 	if (IS_ERR_OR_NULL(opp) || !opp->available) {

I think we can remove the available check here, as we are jut trying
to find frequency of an OPP we already have. Send a patch for that
please.

> 		pr_err("%s: Invalid parameters\n", __func__);
> 		return 0;
> 
> > 
> 

-- 
viresh