Messages in this thread |  | | Subject | Re: [PATCH 1/2] cpufreq: tegra186: Fix initial frequency | From | Jon Hunter <> | Date | Fri, 31 Jul 2020 13:14:09 +0100 |
| |
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 && 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?
Cheers Jon
-- nvpublic
|  |