Messages in this thread | | | Date | Mon, 29 Apr 2024 14:55:15 +0530 | From | Viresh Kumar <> | Subject | Re: [PATCH v4 4/4] cpufreq: Use arch specific feedback for cpuinfo_cur_freq |
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On 26-04-24, 12:45, Beata Michalska wrote: > It seems that we might need to revisit the discussion we've had around > scaling_cur_freq and cpuinfo_cur_freq and the use of arch_freq_get_on_cpu. > As Vanshi has raised, having both utilizing arch specific feedback for > getting current frequency is bit problematic and might be confusing at best. > As arch_freq_get_on_cpu is already used by show_scaling_cur_freq there are not > many options we are left with, if we want to kee all archs aligned: > we can either try to rework show_scaling_cur_freq and it's use of > arch_freq_get_on_cpu, and move it to cpuinfo_cur_freq, which would align with > relevant docs, though that will not work for x86, or we keep it only there and > skip updating cpuinfo_cur_freq, going against the guidelines. Other options, > purely theoretical, would involve making arch_freq_get_on_cpu aware of type of > the info requested (hw vs sw) or adding yet another arch-specific implementation, > and those are not really appealing alternatives to say at least. > What's your opinion on this one ?
Hi Beata / Vanshidhar,
Lets forget for once what X86 and ARM may have done and think about it once again. I also had a chat with Vincent today about this.
The documentation says it clearly, cpuinfo_cur_freq is the one received from hardware and scaling_cur_freq is the one requested from software.
Now, I know that X86 has made both of them quite similar and I suggested to make them all aligned (and never received a reply on my previous message).
There are few reasons why it may be worth keeping the definition (and behavior) of the sysfs files as is, at least for ARM: - First is that the documentation says so. - There is no point providing the same information via both the interfaces, there are two interfaces here for a reason. - There maybe tools around which depend on the documented behavior. - From userspace, currently there is only one way to know the exact frequency that the cpufreq governors have requested from a platform, i.e. the value from scaling_cur_freq. If we make it similar to cpuinfo_cur_freq, then userspace will never know about the requested frequency and the eventual one and if they are same or different.
Lets keep the behavior as is and update only cpuinfo_cur_freq with arch_freq_get_on_cpu().
Makes sense ?
-- viresh
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