Date:   Thu, 14 Jan 2021 16:54:27 +0000
From:   Cristian Marussi <cristian.marussi@....com>
To:     Nicola Mazzucato <nicola.mazzucato@....com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-pm@...r.kernel.org, sudeep.holla@....com, rjw@...ysocki.net,
        vireshk@...nel.org, morten.rasmussen@....com, chris.redpath@....com
Subject: Re: [PATCH v6 2/4] scmi-cpufreq: Move CPU initialisation to probe

Hi Nicola,

a few remarks down below.

On Mon, Jan 11, 2021 at 03:45:22PM +0000, Nicola Mazzucato wrote:
> Some of the cpu related initialisation can be done at probe stage.
> This patch moves those initialisations from the ->init callback to the
> probe stage.
> 
> This is done in preparation for adding support to retrieve additional
> information from DT (CPUs sharing v/f lines).
> 
> Signed-off-by: Nicola Mazzucato <nicola.mazzucato@....com>
> ---
>  drivers/cpufreq/scmi-cpufreq.c | 180 ++++++++++++++++++++++++---------
>  1 file changed, 135 insertions(+), 45 deletions(-)
> 
> diff --git a/drivers/cpufreq/scmi-cpufreq.c b/drivers/cpufreq/scmi-cpufreq.c
> index 15b213ed78fa..4aa97cdc5997 100644
> --- a/drivers/cpufreq/scmi-cpufreq.c
> +++ b/drivers/cpufreq/scmi-cpufreq.c
> @@ -25,6 +25,14 @@ struct scmi_data {
>  	struct device *cpu_dev;
>  };
>  
> +/* Per-CPU storage for runtime management */
> +struct scmi_cpudata {
> +	cpumask_var_t scmi_shared_cpus;
> +	struct cpufreq_frequency_table *freq_table;
> +};
> +
> +static struct scmi_cpudata *cpudata_table;
> +
>  static const struct scmi_handle *handle;
>  
>  static unsigned int scmi_cpufreq_get_rate(unsigned int cpu)
> @@ -120,13 +128,10 @@ scmi_get_cpu_power(unsigned long *power, unsigned long *KHz,
>  
>  static int scmi_cpufreq_init(struct cpufreq_policy *policy)
>  {
> -	int ret, nr_opp;
> +	int ret;
>  	unsigned int latency;
>  	struct device *cpu_dev;
>  	struct scmi_data *priv;
> -	struct cpufreq_frequency_table *freq_table;
> -	struct em_data_callback em_cb = EM_DATA_CB(scmi_get_cpu_power);
> -	bool power_scale_mw;
>  
>  	cpu_dev = get_cpu_device(policy->cpu);
>  	if (!cpu_dev) {
> @@ -134,42 +139,19 @@ static int scmi_cpufreq_init(struct cpufreq_policy *policy)
>  		return -ENODEV;
>  	}
>  
> -	ret = handle->perf_ops->device_opps_add(handle, cpu_dev);
> -	if (ret) {
> -		dev_warn(cpu_dev, "failed to add opps to the device\n");
> -		return ret;
> -	}
> -
> -	ret = scmi_get_sharing_cpus(cpu_dev, policy->cpus);
> -	if (ret) {
> -		dev_warn(cpu_dev, "failed to get sharing cpumask\n");
> -		return ret;
> -	}
> -
> -	ret = dev_pm_opp_set_sharing_cpus(cpu_dev, policy->cpus);
> -	if (ret) {
> -		dev_err(cpu_dev, "%s: failed to mark OPPs as shared: %d\n",
> -			__func__, ret);
> -		return ret;
> -	}
> -
>  	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
>  	if (!priv) {
>  		ret = -ENOMEM;
>  		goto out_free_opp;
>  	}
>  
> -	ret = dev_pm_opp_init_cpufreq_table(cpu_dev, &freq_table);
> -	if (ret) {
> -		dev_err(cpu_dev, "failed to init cpufreq table: %d\n", ret);
> -		goto out_free_priv;
> -	}
> +	cpumask_copy(policy->cpus, cpudata_table[policy->cpu].scmi_shared_cpus);
>  
>  	priv->cpu_dev = cpu_dev;
>  	priv->domain_id = handle->perf_ops->device_domain_id(cpu_dev);
>  
>  	policy->driver_data = priv;
> -	policy->freq_table = freq_table;
> +	policy->freq_table = cpudata_table[policy->cpu].freq_table;
>  
>  	/* SCMI allows DVFS request for any domain from any CPU */
>  	policy->dvfs_possible_from_any_cpu = true;
> @@ -183,23 +165,8 @@ static int scmi_cpufreq_init(struct cpufreq_policy *policy)
>  	policy->fast_switch_possible =
>  		handle->perf_ops->fast_switch_possible(handle, cpu_dev);
>  
> -	nr_opp = dev_pm_opp_get_opp_count(cpu_dev);
> -	if (nr_opp <= 0) {
> -		dev_err(cpu_dev, "%s: No OPPs for this device: %d\n",
> -			__func__, ret);
> -
> -		ret = -ENODEV;
> -		goto out_free_priv;
> -	}
> -
> -	power_scale_mw = handle->perf_ops->power_scale_mw_get(handle);
> -	em_dev_register_perf_domain(cpu_dev, nr_opp, &em_cb, policy->cpus,
> -				    power_scale_mw);
> -
>  	return 0;
>  
> -out_free_priv:
> -	kfree(priv);
>  out_free_opp:
>  	dev_pm_opp_remove_all_dynamic(cpu_dev);
>  

My understanding (but I could be wrong given my limited familiarity with
CPUFREQ ... so bear with me) is that dev_pm_opp_remove_all_dynamic() is
meant to clean dynamic OPPs added by dev_pm_opp_add() which in turn in
this driver is folded inside the handle->perf_ops->device_opps_add() call,
so is not that this call should be added also on the error path inside
the new scmi_init_device() ? (this was already faulty this way in the
original code to be honest...if faulty at all :D)

I added a few such invocations down below as rough untested example of
what I mean.

> @@ -210,7 +177,6 @@ static int scmi_cpufreq_exit(struct cpufreq_policy *policy)
>  {
>  	struct scmi_data *priv = policy->driver_data;
>  
> -	dev_pm_opp_free_cpufreq_table(priv->cpu_dev, &policy->freq_table);
>  	dev_pm_opp_remove_all_dynamic(priv->cpu_dev);
>  	kfree(priv);
>  
> @@ -231,10 +197,102 @@ static struct cpufreq_driver scmi_cpufreq_driver = {
>  	.exit	= scmi_cpufreq_exit,
>  };
>  
> +static int scmi_init_cpudata(void)
> +{
> +	int cpu;
> +	unsigned int ncpus = num_possible_cpus();
> +
> +	cpudata_table = kzalloc(sizeof(*cpudata_table) * ncpus, GFP_KERNEL);
Shouldn/t this be a kcalloc() given it's an array allocation, checkpatch
complains too.

> +	if (!cpudata_table)
> +		return -ENOMEM;
> +
> +	for_each_possible_cpu(cpu) {
> +		if (!zalloc_cpumask_var(&cpudata_table[cpu].scmi_shared_cpus,
> +					GFP_KERNEL))
> +			goto out;
> +	}
> +
> +	return 0;
> +
> +out:
> +	kfree(cpudata_table);
> +	return -ENOMEM;
> +}
> +
> +static int scmi_init_device(const struct scmi_handle *handle, int cpu)
> +{
> +	struct device *cpu_dev;
> +	int ret, nr_opp;
> +	struct em_data_callback em_cb = EM_DATA_CB(scmi_get_cpu_power);
> +	bool power_scale_mw;
> +	cpumask_var_t scmi_cpus;
> +
> +	if (!zalloc_cpumask_var(&scmi_cpus, GFP_KERNEL))
> +		return -ENOMEM;
> +
> +	cpumask_set_cpu(cpu, scmi_cpus);
> +
> +	cpu_dev = get_cpu_device(cpu);
> +
> +	ret = scmi_get_sharing_cpus(cpu_dev, scmi_cpus);
> +	if (ret) {
> +		dev_warn(cpu_dev, "failed to get sharing cpumask\n");
> +		goto free_cpumask;
> +	}
> +
> +	/*
> +	 * We get here for each CPU. Add OPPs only on those CPUs for which we
> +	 * haven't already done so, or set their OPPs as shared.
> +	 */
> +	nr_opp = dev_pm_opp_get_opp_count(cpu_dev);
> +	if (nr_opp <= 0) {
> +		ret = handle->perf_ops->device_opps_add(handle, cpu_dev);
> +		if (ret) {
> +			dev_warn(cpu_dev, "failed to add opps to the device\n");
> +			goto free_cpumask;
> +		}
> +
> +		ret = dev_pm_opp_set_sharing_cpus(cpu_dev, scmi_cpus);
> +		if (ret) {
> +			dev_err(cpu_dev, "%s: failed to mark OPPs as shared: %d\n",
> +				__func__, ret);
			goto free_dynamic_opps;
> +		}
> +
> +		nr_opp = dev_pm_opp_get_opp_count(cpu_dev);
> +		if (nr_opp <= 0) {
> +			dev_err(cpu_dev, "%s: No OPPs for this device: %d\n",
> +				__func__, ret);
> +
> +			ret = -ENODEV;
			goto free_dynamic_opps;
> +		}
> +
> +		power_scale_mw = handle->perf_ops->power_scale_mw_get(handle);
> +		em_dev_register_perf_domain(cpu_dev, nr_opp, &em_cb, scmi_cpus,
> +					    power_scale_mw);
> +	}
> +
> +	ret = dev_pm_opp_init_cpufreq_table(cpu_dev,
> +					    &cpudata_table[cpu].freq_table);
> +	if (ret) {
> +		dev_err(cpu_dev, "failed to init cpufreq table: %d\n", ret);
		goto free_dynamic_opps;
> +	}
> +
> +	cpumask_copy(cpudata_table[cpu].scmi_shared_cpus, scmi_cpus);
> +
   free_dynamic_opps:
	   dev_pm_opp_remove_all_dynamic(cpu_dev);
> +free_cpumask:
> +	free_cpumask_var(scmi_cpus);
> +	return ret;
> +}
> +
>  static int scmi_cpufreq_probe(struct scmi_device *sdev)
>  {
>  	int ret;
>  	struct device *dev = &sdev->dev;
> +	int cpu;
> +	struct device *cpu_dev;
>  
>  	handle = sdev->handle;
>  
> @@ -247,6 +305,24 @@ static int scmi_cpufreq_probe(struct scmi_device *sdev)
>  		devm_of_clk_add_hw_provider(dev, of_clk_hw_simple_get, NULL);
>  #endif
>  
> +	ret = scmi_init_cpudata();
> +	if (ret) {
> +		pr_err("%s: init cpu data failed\n", __func__);
> +		return ret;
> +	}
> +
> +	for_each_possible_cpu(cpu) {
> +		cpu_dev = get_cpu_device(cpu);
> +
> +		ret = scmi_init_device(handle, cpu);
> +		if (ret) {
> +			dev_err(cpu_dev, "%s: init device failed\n",
> +				__func__);
> +
			goto clean;
> +		}
> +	}
> +
>  	ret = cpufreq_register_driver(&scmi_cpufreq_driver);
>  	if (ret) {
>  		dev_err(dev, "%s: registering cpufreq failed, err: %d\n",

	/* clean any dynamic OPPs already set */
clean:
	for_each_possible_cpu(cpu) {
		cpu_dev = get_cpu_device(cpu);

		dev_pm_opp_remove_all_dynamic(cpu_dev);
	}

	return ret;
}


Thanks

Cristian

> @@ -258,6 +334,20 @@ static int scmi_cpufreq_probe(struct scmi_device *sdev)
>  
>  static void scmi_cpufreq_remove(struct scmi_device *sdev)
>  {
> +	int cpu;
> +	struct device *cpu_dev;
> +
> +	for_each_possible_cpu(cpu) {
> +		cpu_dev = get_cpu_device(cpu);
> +
> +		dev_pm_opp_free_cpufreq_table(cpu_dev,
> +					      &cpudata_table[cpu].freq_table);
> +
> +		free_cpumask_var(cpudata_table[cpu].scmi_shared_cpus);
> +	}
> +
> +	kfree(cpudata_table);
> +
>  	cpufreq_unregister_driver(&scmi_cpufreq_driver);
>  }
>  
> -- 
> 2.27.0
> 

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