linux-kernel - Re: [PATCH v6 4/5] cpufreq: qcom: Update the bandwidth levels on frequency change

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Message-ID: <20200618170536.GF4525@google.com>
Date:   Thu, 18 Jun 2020 10:05:36 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Sibi Sankar <sibis@...eaurora.org>
Cc:     viresh.kumar@...aro.org, sboyd@...nel.org,
        georgi.djakov@...aro.org, saravanak@...gle.com, nm@...com,
        bjorn.andersson@...aro.org, agross@...nel.org, rjw@...ysocki.net,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, dianders@...omium.org,
        vincent.guittot@...aro.org, amit.kucheria@...aro.org,
        lukasz.luba@....com, sudeep.holla@....com, smasetty@...eaurora.org,
        linux-arm-msm-owner@...r.kernel.org
Subject: Re: [PATCH v6 4/5] cpufreq: qcom: Update the bandwidth levels on
 frequency change

On Wed, Jun 17, 2020 at 10:13:21PM +0530, Sibi Sankar wrote:
> On 2020-06-17 03:41, Matthias Kaehlcke wrote:
> > Hi Sibi,
> > 
> > after doing the review I noticed that Viresh replied on the cover letter
> > that he picked the series up for v5.9, so I'm not sure if it makes sense
> > to send a v7.
> > 
> > On Wed, Jun 17, 2020 at 02:35:00AM +0530, Sibi Sankar wrote:
> > 
> > > > > @@ -112,7 +178,7 @@ static int qcom_cpufreq_hw_read_lut(struct
> > > > > device *cpu_dev,
> > > > >
> > > > >  		if (freq != prev_freq && core_count != LUT_TURBO_IND) {
> > > > >  			table[i].frequency = freq;
> > > > > -			dev_pm_opp_add(cpu_dev, freq * 1000, volt);
> > > > > +			qcom_cpufreq_update_opp(cpu_dev, freq, volt);
> > > >
> > > > This is the cross-validation mentioned above, right? Shouldn't it
> > > > include
> > > > a check of the return value?
> > > 
> > > Yes, this is the cross-validation step,
> > > we adjust the voltage if opp-tables are
> > > present/added successfully and enable
> > > them, else we would just do a add opp.
> > > We don't want to exit early on a single
> > > opp failure. We will error out a bit
> > > later if the opp-count ends up to be
> > > zero.
> > 
> > At least an error/warning message would seem convenient when
> > adjusting/adding
> > an OPP fails, otherwise you would only notice by looking at the sysfs
> > attributes (if you'd even spot a single/few OPPs to be missing).
> 
> I did consider the case where adjust
> voltage fails and we do report the
> freq for which it fails for as well.
> If adding a OPP fails we will still
> it being listed in the sysfs cpufreq
> scaling_available_frequencies since
> it lists the freq_table in khz there
> instead.

Ah, right, I missed that v6 added the error log to
qcom_cpufreq_update_opp(), please ignore my comment :)