Re: [TEGRA194_CPUFREQ Patch v2 2/3] cpufreq: Add Tegra194 cpufreq driver

[Dmitry Osipenko]

07.04.2020 21:55, sumitg ÐÐÑÐÑ:
...
>>> + * Returns freq in KHz on success, 0 if cpu is offline
>>
>> I don't see any checks in the code about whether CPU is offline.
>>
>> Googling for "queue_work_on offline cpu" suggests that this function
>> should hang.
>>
> Tried this and didn't get crash or hang.
> show_cpuinfo_cur_freq() returns "<unknown>" value on reading frequency
> from a cluster having both it's cores offline.
> If only one cpu is offline, then frequency of other online cpu which is
> managing the policy of that cluster is returned.
> Have still added below check as guard in get|set() freq calls.
> ÂÂÂÂif (!cpu_online(cpu))
> ÂÂÂÂÂÂÂ return -EINVAL;
> Thankyou for the input.

If CPUFreq core takes care of taking into account the offline CPU, then
the check isn't needed. It also wouldn't be enough if there was a
problem here.