linux-kernel - Re: [Patch 2/2] cpufreq: tegra194: Fix unlisted boot freq warning

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Date:   Tue, 6 Oct 2020 11:08:56 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Sumit Gupta <sumitg@...dia.com>
Cc:     rjw@...ysocki.net, thierry.reding@...il.com, jonathanh@...dia.com,
        linux-pm@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        ksitaraman@...dia.com, bbasu@...dia.com
Subject: Re: [Patch 2/2] cpufreq: tegra194: Fix unlisted boot freq warning

On 06-10-20, 00:24, Sumit Gupta wrote:
> 
> > > Warning coming during boot because the boot freq set by bootloader
> > > gets filtered out due to big freq steps while creating freq_table.
> > > Fixing this by setting closest ndiv value from freq_table.
> > > Warning:
> > >    cpufreq: cpufreq_online: CPU0: Running at unlisted freq
> > >    cpufreq: cpufreq_online: CPU0: Unlisted initial frequency changed
> > > 
> > > Also, added change in init to wait till current frequency becomes
> > > equal or near to the previously requested frequency. This is done
> > > because it takes some time to restore the previous frequency while
> > > turning-on non-boot cores during exit from SC7(Suspend-to-RAM).
> > 
> > So you are trying to figure if the frequency is listed in freq-table or not,
> > otherwise setting the frequency to a value you think is appropriate. Right ?
> During boot, want to set the frequency from freq_table which is closest to
> the one set by bootloader.

Right.

> During resume from suspend-to-idle, want to restore the frequency which was
> set on non-boot cores before they were hotplug powered off.

Why exactly do you want to do that ? Rather you should provide
online/offline hooks for the cpufreq driver and do light-weight
suspend/resume as is done by cpufreq-dt.c as well.

> > 
> > This is what the cpufreq core already does when it printed these boot time
> > messages. Do we really need to add this much code in here ?
> We want to avoid the warning messages.

Hmm, okay.

> > 
> > If you really don't want to see the warning, how about fixing it the way cpufreq
> > core does ? i.e. with this call:
> > 
> > ret = __cpufreq_driver_target(policy, policy->cur - 1, CPUFREQ_RELATION_L);
> > 
> The cpufreq core change will help in bootup case but not during the case of
> resume.
> In this change, reading the previously stored value and restoring it will
> also fix the warning message during resume.

You were getting the message during resume as well ? Why ? The
firmware is updating the frequency to a previous value ? If that is
so, you should just set the frequency again to some other value during
resume to fix it.

-- 
viresh