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SubjectRe: [PATCH 1/2] cpufreq: tegra186: Fix initial frequency
Hi Viresh,

On 14/07/2020 04:46, Viresh Kumar wrote:


> The get() callback is supposed to read the frequency from hardware and
> return it, no cached value here. policy->cur may end up being wrong in
> case there is a bug.

I have been doing some more testing on Tegra, I noticed that when
reading the current CPU frequency via the sysfs scaling_cur_freq entry,
this always returns the cached value (at least for Tegra). Looking at
the implementation of scaling_cur_freq I see ...

static ssize_t show_scaling_cur_freq(struct cpufreq_policy *policy, char *buf)
ssize_t ret;
unsigned int freq;

freq = arch_freq_get_on_cpu(policy->cpu);
if (freq)
ret = sprintf(buf, "%u\n", freq);
else if (cpufreq_driver && cpufreq_driver->setpolicy &&
ret = sprintf(buf, "%u\n", cpufreq_driver->get(policy->cpu));
ret = sprintf(buf, "%u\n", policy->cur);
return ret;

The various Tegra CPU frequency drivers do not implement the
set_policy callback and hence why we always get the cached value. I
see the following commit added this and before it simply return the
cached value ...

commit c034b02e213d271b98c45c4a7b54af8f69aaac1e
Author: Dirk Brandewie <>
Date: Mon Oct 13 08:37:40 2014 -0700

cpufreq: expose scaling_cur_freq sysfs file for set_policy() drivers

Is this intentional?



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