linux-kernel - Re: [PATCH] cpufreq: freq_table: Initialize cpuinfo.max

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Date:   Tue, 16 Nov 2021 09:29:35 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Steev Klimaszewski <steev@...i.org>
Cc:     Thara Gopinath <thara.gopinath@...aro.org>, rafael@...nel.org,
        bjorn.andersson@...aro.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH] cpufreq: freq_table: Initialize cpuinfo.max_freq to
 correct max frequency.

On 15-11-21, 19:23, Steev Klimaszewski wrote:
> Hi Thara,
> 
> On 11/15/21 1:50 PM, Thara Gopinath wrote:
> > cpuinfo.max_freq reflects the maximum supported frequency of cpus in a
> > cpufreq policy. When cpus support boost frequency and if boost is disabled
> > during boot up (which is the default), cpuinfo.max_freq does not reflect
> > boost frequency as the maximum supported frequency till boost is explicitly
> > enabled via sysfs interface later. This also means that policy reports two
> > different cpuinfo.max_freq before and after turning on boost.  Fix this by
> > separating out setting of policy->max and cpuinfo.max_freq in
> > cpufreq_frequency_table_cpuinfo.
> > 
> > e.g. of the problem. Qualcomm sdm845 supports boost frequency for gold
> > cluster (cpus 4-7). After boot up (boost disabled),
> > 
> > 1.  cat /sys/devices/system/cpu/cpufreq/policy4/cpuinfo_max_freq 2649600
> > <- This is wrong because boost frequency is
> > 
> > 2.  echo 1 > /sys/devices/system/cpu/cpufreq/boost  <- Enable boost cat
> > /sys/devices/system/cpu/cpufreq/policy4/cpuinfo_max_freq 2803200	<-
> > max freq reflects boost freq.
> > 
> > 3.  echo 0 > /sys/devices/system/cpu/cpufreq/boost <- Disable boost cat
> > /sys/devices/system/cpu/cpufreq/policy4/cpuinfo_max_freq 2803200	<-
> > Discrepancy with step 1 as in both cases boost is disabled.
> > 
> > Note that the other way to fix this is to set cpuinfo.max_freq in Soc
> > cpufreq driver during initialization. Fixing it in
> > cpufreq_frequency_table_cpuinfo seems more generic solution
> > 
> > Signed-off-by: Thara Gopinath <thara.gopinath@...aro.org>
> > ---
> >   drivers/cpufreq/freq_table.c | 8 ++++++--
> >   1 file changed, 6 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/cpufreq/freq_table.c b/drivers/cpufreq/freq_table.c
> > index 67e56cf638ef..6784f94124df 100644
> > --- a/drivers/cpufreq/freq_table.c
> > +++ b/drivers/cpufreq/freq_table.c
> > @@ -35,11 +35,15 @@ int cpufreq_frequency_table_cpuinfo(struct cpufreq_policy *policy,
> >   	struct cpufreq_frequency_table *pos;
> >   	unsigned int min_freq = ~0;
> >   	unsigned int max_freq = 0;
> > +	unsigned int cpuinfo_max_freq = 0;
> >   	unsigned int freq;
> >   	cpufreq_for_each_valid_entry(pos, table) {
> >   		freq = pos->frequency;
> > +		if (freq > cpuinfo_max_freq)
> > +			cpuinfo_max_freq = freq;
> > +
> >   		if (!cpufreq_boost_enabled()
> >   		    && (pos->flags & CPUFREQ_BOOST_FREQ))
> >   			continue;
> > @@ -57,8 +61,8 @@ int cpufreq_frequency_table_cpuinfo(struct cpufreq_policy *policy,
> >   	 * If the driver has set its own cpuinfo.max_freq above max_freq, leave
> >   	 * it as is.
> >   	 */
> > -	if (policy->cpuinfo.max_freq < max_freq)
> > -		policy->max = policy->cpuinfo.max_freq = max_freq;
> > +	if (policy->cpuinfo.max_freq < cpuinfo_max_freq)
> > +		policy->cpuinfo.max_freq = cpuinfo_max_freq;

You need to keep the check of policy->max here and update policy->max,
else you will never run at boost freq. I think this is what Steev
reported as well ?

So basically something like this:

	if (policy->max < max_freq)
		policy->max = max_freq;

	if (policy->cpuinfo.max_freq < cpuinfo_max_freq)
		policy->cpuinfo.max_freq = cpuinfo_max_freq;

-- 
viresh