Subject: Re: [PATCH v4 1/4] PM / EM: add devices to Energy Model

From: Quentin Perret <[email-masked]>
Date: Fri, 13 Mar 2020 10:04:07 +0000

Hi Lukasz,

On Monday 09 Mar 2020 at 13:41:14 (+0000), Lukasz Luba wrote:
<snip>
> diff --git a/drivers/opp/of.c b/drivers/opp/of.c
> index 9cd8f0adacae..0efd6cf6d023 100644
> --- a/drivers/opp/of.c
> +++ b/drivers/opp/of.c
> @@ -1047,9 +1047,8 @@ EXPORT_SYMBOL_GPL(dev_pm_opp_get_of_node);
>   * calculation failed because of missing parameters, 0 otherwise.
>   */
>  static int __maybe_unused _get_cpu_power(unsigned long *mW, unsigned long *kHz,
> -					 int cpu)
> +					 struct device *cpu_dev)
>  {
> -	struct device *cpu_dev;
>  	struct dev_pm_opp *opp;
>  	struct device_node *np;
>  	unsigned long mV, Hz;
> @@ -1057,10 +1056,6 @@ static int __maybe_unused _get_cpu_power(unsigned long *mW, unsigned long *kHz,
>  	u64 tmp;
>  	int ret;
>  
> -	cpu_dev = get_cpu_device(cpu);
> -	if (!cpu_dev)
> -		return -ENODEV;
> -
>  	np = of_node_get(cpu_dev->of_node);
>  	if (!np)
>  		return -EINVAL;
> @@ -1128,6 +1123,6 @@ void dev_pm_opp_of_register_em(struct cpumask *cpus)
>  	if (ret || !cap)
>  		return;
>  
> -	em_register_perf_domain(cpus, nr_opp, &em_cb);
> +	em_register_perf_domain(cpu_dev, nr_opp, &em_cb, cpus);

Any reason for not checking the return value here ? You added a nice
check in scmi_get_cpu_power(), perhaps do the same thing here ?

>  }
>  EXPORT_SYMBOL_GPL(dev_pm_opp_of_register_em);
> diff --git a/drivers/thermal/cpufreq_cooling.c b/drivers/thermal/cpufreq_cooling.c
> index fe83d7a210d4..fcf2dab1b3b8 100644
> --- a/drivers/thermal/cpufreq_cooling.c
> +++ b/drivers/thermal/cpufreq_cooling.c
> @@ -333,18 +333,18 @@ static inline bool em_is_sane(struct cpufreq_cooling_device *cpufreq_cdev,
>  		return false;
>  
>  	policy = cpufreq_cdev->policy;
> -	if (!cpumask_equal(policy->related_cpus, to_cpumask(em->cpus))) {
> +	if (!cpumask_equal(policy->related_cpus, em_span_cpus(em))) {
>  		pr_err("The span of pd %*pbl is misaligned with cpufreq policy %*pbl\n",
> -			cpumask_pr_args(to_cpumask(em->cpus)),
> +			cpumask_pr_args(em_span_cpus(em)),
>  			cpumask_pr_args(policy->related_cpus));
>  		return false;
>  	}
>  
>  	nr_levels = cpufreq_cdev->max_level + 1;
> -	if (em->nr_cap_states != nr_levels) {
> +	if (em->nr_perf_states != nr_levels) {
>  		pr_err("The number of cap states in pd %*pbl (%u) doesn't match the number of cooling levels (%u)\n",

s/cap states/performance states

> -			cpumask_pr_args(to_cpumask(em->cpus)),
> -			em->nr_cap_states, nr_levels);
> +			cpumask_pr_args(em_span_cpus(em)),
> +			em->nr_perf_states, nr_levels);
>  		return false;
>  	}

<snip>
> +static int em_create_perf_table(struct device *dev, struct em_perf_domain *pd,
> +				int nr_states, struct em_data_callback *cb)
>  {
>  	unsigned long opp_eff, prev_opp_eff = ULONG_MAX;
>  	unsigned long power, freq, prev_freq = 0;
> -	int i, ret, cpu = cpumask_first(span);
> -	struct em_cap_state *table;
> -	struct em_perf_domain *pd;
> +	struct em_perf_state *table;
> +	int i, ret;
>  	u64 fmax;
>  
> -	if (!cb->active_power)
> -		return NULL;
> -
> -	pd = kzalloc(sizeof(*pd) + cpumask_size(), GFP_KERNEL);
> -	if (!pd)
> -		return NULL;
> -
>  	table = kcalloc(nr_states, sizeof(*table), GFP_KERNEL);
>  	if (!table)
> -		goto free_pd;
> +		return -ENOMEM;
>  
> -	/* Build the list of capacity states for this performance domain */
> +	/* Build the list of performance states for this performance domain */
>  	for (i = 0, freq = 0; i < nr_states; i++, freq++) {
>  		/*
>  		 * active_power() is a driver callback which ceils 'freq' to
> -		 * lowest capacity state of 'cpu' above 'freq' and updates
> +		 * lowest performance state of 'dev' above 'freq' and updates
>  		 * 'power' and 'freq' accordingly.
>  		 */
> -		ret = cb->active_power(&power, &freq, cpu);
> +		ret = cb->active_power(&power, &freq, dev);
>  		if (ret) {
> -			pr_err("pd%d: invalid cap. state: %d\n", cpu, ret);
> +			dev_err(dev, "EM: invalid perf. state: %d\n",
> +				ret);

Not easy to figure out which device has a problem with this. I'm
guessing you went that way since this is called before ida_simple_get() ?
Could that be refactored to make the error message more useful ?

>  			goto free_cs_table;
>  		}

<snip>
> +/**
> + * em_unregister_perf_domain() - Unregister Energy Model (EM) for the device
> + * @dev		: Device for which the EM is registered
> + *
> + * Try to unregister the EM for the specified device (it checks current
> + * reference counter). The EM for CPUs will not be freed.
> + */
> +void em_unregister_perf_domain(struct device *dev)
> +{
> +	struct em_device *em_dev, *tmp;
> +
> +	if (IS_ERR_OR_NULL(dev))
> +		return;
> +
> +	/* We don't support freeing CPU structures in hotplug */
> +	if (_is_cpu_device(dev))
> +		return;

Can we WARN() here ?

> +
> +	mutex_lock(&em_pd_mutex);
> +
> +	if (list_empty(&em_pd_dev_list)) {
> +		mutex_unlock(&em_pd_mutex);
> +		return;
> +	}
> +
> +	list_for_each_entry_safe(em_dev, tmp, &em_pd_dev_list, em_dev_list) {
> +		if (em_dev->dev == dev) {
> +			kref_put(&em_dev->kref, _em_release);
> +			break;
> +		}
> +	}
> +
> +	mutex_unlock(&em_pd_mutex);
> +}
> +EXPORT_SYMBOL_GPL(em_unregister_perf_domain);

Otherwise this looks pretty good to me. So, with these small nits
addressed:

  Acked-by: Quentin Perret <[email-masked]>

Thanks!
Quentin

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