linux-kernel - Re: [Patch] cpufreq: tegra194: remove opp table in exit hook

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Message-ID: <17b11665-874a-5b06-bc97-70f5202f238b@nvidia.com>
Date:   Mon, 14 Aug 2023 23:43:02 +0530
From:   Sumit Gupta <sumitg@...dia.com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
CC:     <rafael@...nel.org>, <treding@...dia.com>, <jonathanh@...dia.com>,
        <linux-pm@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <bbasu@...dia.com>,
        Sumit Gupta <sumitg@...dia.com>
Subject: Re: [Patch] cpufreq: tegra194: remove opp table in exit hook



On 10/08/23 11:01, Viresh Kumar wrote:
> External email: Use caution opening links or attachments
> 
> 
> On 09-08-23, 21:04, Sumit Gupta wrote:
>> Add exit hook and remove OPP table when all the CPU's in a policy
>> are offlined. It will fix the below error messages when onlining
>> first CPU from a policy whose all CPU's were previously offlined.
>>
>>   debugfs: File 'cpu5' in directory 'opp' already present!
>>   debugfs: File 'cpu6' in directory 'opp' already present!
>>   debugfs: File 'cpu7' in directory 'opp' already present!
>>
>> Fixes: f41e1442ac5b ("cpufreq: tegra194: add OPP support and set bandwidth")
>> Signed-off-by: Sumit Gupta <sumitg@...dia.com>
>> ---
>>   drivers/cpufreq/tegra194-cpufreq.c | 13 +++++++++++++
>>   1 file changed, 13 insertions(+)
>>
>> diff --git a/drivers/cpufreq/tegra194-cpufreq.c b/drivers/cpufreq/tegra194-cpufreq.c
>> index c90b30469165..66a9c23544db 100644
>> --- a/drivers/cpufreq/tegra194-cpufreq.c
>> +++ b/drivers/cpufreq/tegra194-cpufreq.c
>> @@ -454,6 +454,8 @@ static int tegra_cpufreq_init_cpufreq_table(struct cpufreq_policy *policy,
>>                if (ret < 0)
>>                        return ret;
>>
>> +             dev_pm_opp_put(opp);
>> +
>>                freq_table[j].driver_data = pos->driver_data;
>>                freq_table[j].frequency = pos->frequency;
>>                j++;
>> @@ -508,6 +510,16 @@ static int tegra194_cpufreq_init(struct cpufreq_policy *policy)
>>        return 0;
>>   }
>>
>> +static int tegra194_cpufreq_exit(struct cpufreq_policy *policy)
>> +{
>> +     struct device *cpu_dev = get_cpu_device(policy->cpu);
>> +
>> +     dev_pm_opp_remove_all_dynamic(cpu_dev);
>> +     dev_pm_opp_of_cpumask_remove_table(policy->related_cpus);
>> +
>> +     return 0;
>> +}
>> +
>>   static int tegra194_cpufreq_set_target(struct cpufreq_policy *policy,
>>                                       unsigned int index)
>>   {
>> @@ -535,6 +547,7 @@ static struct cpufreq_driver tegra194_cpufreq_driver = {
>>        .target_index = tegra194_cpufreq_set_target,
>>        .get = tegra194_get_speed,
>>        .init = tegra194_cpufreq_init,
>> +     .exit = tegra194_cpufreq_exit,
>>        .attr = cpufreq_generic_attr,
>>   };
> 
> If it is only about hotplugging of the CPUs, then you can also do this I guess.
> 
> commit 263abfe74b5f ("cpufreq: dt: Implement online/offline() callbacks")
> 
> But since your driver is capable of being built as a module, I suggest you try
> to build it as one and insert remove it multiple times. It must cause you some
> trouble as you don't implement an .exit() before this patch.
> 
> Eventually, I think you need to do both, what this patch and 263abfe74b5f do.
> Just that the reasons need to be correct for both the changes.
> 
> --
> viresh

Hi Viresh,
I got the same message on inserting and removing the module multiple 
times as you suggested. After applying this change, the message is not 
coming. So, the current change is resolving both scenarios as 
__cpufreq_offline() calls either exit() or offline().
I can update the commit message to mention both scenarios and keep 
change as it is?

   cpufreq_remove_dev
   |-__cpufreq_offline
   |--tegra194_cpufreq_exit

   cpuhp_cpufreq_offline
   |-__cpufreq_offline
   |--tegra194_cpufreq_exit

Thank you,
Sumit Gupta