From: Viresh Kumar <viresh.kumar@linaro.org>
To: Jon Hunter <jonathanh@nvidia.com>
Cc: Thierry Reding <thierry.reding@gmail.com>,
"Rafael J . Wysocki" <rjw@rjwysocki.net>,
linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] cpufreq: tegra186: Fix initial frequency
Date: Tue, 4 Aug 2020 10:55:09 +0530 [thread overview]
Message-ID: <20200804052509.24en7voy2bg6vdbc@vireshk-mac-ubuntu> (raw)
In-Reply-To: <8c6d3c32-c142-3981-3a52-6560e885f4c9@nvidia.com>
On 31-07-20, 13:14, Jon Hunter wrote:
> 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 &&
> cpufreq_driver->get)
> ret = sprintf(buf, "%u\n", cpufreq_driver->get(policy->cpu));
> else
> 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 <dirk.j.brandewie@intel.com>
> Date: Mon Oct 13 08:37:40 2014 -0700
>
> cpufreq: expose scaling_cur_freq sysfs file for set_policy() drivers
>
> Is this intentional?
Yes, it is.
There are two sysfs files to read the current frequency.
- scaling_cur_freq: as you noticed it returns cached value unless it is for
setpolicy drivers in whose case cpufreq core doesn't control the frequency and
so doesn't cache any values.
- cpuinfo_cur_freq: This will return the value as read from hardware using
->get() callback.
--
viresh
prev parent reply other threads:[~2020-08-04 5:25 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-12 10:06 [PATCH 1/2] cpufreq: tegra186: Fix initial frequency Jon Hunter
[not found] ` <20200712100645.13927-1-jonathanh-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
2020-07-12 10:06 ` [PATCH 2/2] cpufreq: tegra186: Simplify probe return path Jon Hunter
[not found] ` <20200712100645.13927-2-jonathanh-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
2020-07-13 3:28 ` Viresh Kumar
2020-07-13 3:25 ` [PATCH 1/2] cpufreq: tegra186: Fix initial frequency Viresh Kumar
2020-07-13 16:37 ` Jon Hunter
[not found] ` <3d6091f2-6b04-185f-6c23-e39a34b87877-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
2020-07-14 3:46 ` Viresh Kumar
2020-07-14 7:26 ` Jon Hunter
[not found] ` <aa941c67-1dec-5363-7bd7-5e9d8d324110-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
2020-07-14 7:31 ` Viresh Kumar
2020-07-31 12:14 ` Jon Hunter
2020-08-04 5:25 ` Viresh Kumar [this message]
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