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

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Date:   Thu, 10 Aug 2023 11:01:27 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Sumit Gupta <sumitg@...dia.com>
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
Subject: Re: [Patch] cpufreq: tegra194: remove opp table in exit hook

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