Re: [PATCH 5/8] thermal/drivers/cpu_cooling: Introduce the cpu idle cooling driver

[Viresh Kumar]

On 23-01-18, 16:34, Daniel Lezcano wrote:
> diff --git a/drivers/thermal/cpu_cooling.c b/drivers/thermal/cpu_cooling.c

> +/**
> + * cpuidle_cooling_ops - thermal cooling device ops
> + */
> +static struct thermal_cooling_device_ops cpuidle_cooling_ops = {
> +	.get_max_state = cpuidle_cooling_get_max_state,
> +	.get_cur_state = cpuidle_cooling_get_cur_state,
> +	.set_cur_state = cpuidle_cooling_set_cur_state,
> +};
> +
> +/**
> + * cpuidle_cooling_release - Kref based release helper
> + * @kref: a pointer to the kref structure
> + *
> + * This function is automatically called by the kref_put function when
> + * the idle cooling device refcount reaches zero. At this point, we
> + * have the guarantee the structure is no longer in use and we can
> + * safely release all the ressources.
> + */

Don't really need doc style comments for internal routines.

> +static void __init cpuidle_cooling_release(struct kref *kref)
> +{
> +	struct cpuidle_cooling_device *idle_cdev =
> +		container_of(kref, struct cpuidle_cooling_device, kref);
> +
> +	thermal_cooling_device_unregister(idle_cdev->cdev);
> +	kfree(idle_cdev->waitq);
> +	kfree(idle_cdev->tsk);
> +	kfree(idle_cdev);

What about list-del here (cpuidle_cdev_list) ?

> +}
> +
> +/**
> + * cpuidle_cooling_register - Idle cooling device initialization function
> + *
> + * This function is in charge of creating a cooling device per cluster
> + * and register it to thermal framework. For this we rely on the
> + * topology as there is nothing yet describing better the idle state
> + * power domains.
> + *
> + * For each first CPU of the cluster's cpumask, we allocate the idle
> + * cooling device, initialize the general fields and then we initialze
> + * the rest in a per cpu basis.
> + *
> + * Returns zero on success, < 0 otherwise.
> + */
> +int cpuidle_cooling_register(void)
> +{
> +	struct cpuidle_cooling_device *idle_cdev = NULL;
> +	struct thermal_cooling_device *cdev;
> +	struct task_struct *tsk;
> +	struct device_node *np;
> +	cpumask_t *cpumask;
> +	char dev_name[THERMAL_NAME_LENGTH];
> +	int weight;
> +	int ret = -ENOMEM, cpu;
> +	int index = 0;
> +
> +	for_each_possible_cpu(cpu) {
> +

Perhaps this is coding choice, but just for the sake of consistency in
this driver should we remove such empty lines at the beginning of a
blocks ?

> +		cpumask = topology_core_cpumask(cpu);
> +		weight = cpumask_weight(cpumask);
> +
> +		/*
> +		 * This condition makes the first cpu belonging to the
> +		 * cluster to create a cooling device and allocates
> +		 * the structure. Others CPUs belonging to the same
> +		 * cluster will just increment the refcount on the
> +		 * cooling device structure and initialize it.
> +		 */
> +		if (cpu == cpumask_first(cpumask)) {
> +

Like here as well.

> +			np = of_cpu_device_node_get(cpu);
> +
> +			idle_cdev = kzalloc(sizeof(*idle_cdev), GFP_KERNEL);
> +			if (!idle_cdev)
> +				goto out_fail;
> +
> +			idle_cdev->tsk = kzalloc(sizeof(*idle_cdev->tsk) *
> +						 weight, GFP_KERNEL);
> +			if (!idle_cdev->tsk)
> +				goto out_fail;
> +
> +			idle_cdev->waitq = kzalloc(sizeof(*idle_cdev->waitq) *
> +						   weight, GFP_KERNEL);
> +			if (!idle_cdev->waitq)
> +				goto out_fail;
> +
> +			idle_cdev->idle_cycle = DEFAULT_IDLE_TIME_US;
> +
> +			atomic_set(&idle_cdev->count, 0);
> +
> +			kref_init(&idle_cdev->kref);
> +
> +			/*
> +			 * Initialize the timer to wakeup all the idle
> +			 * injection tasks
> +			 */
> +			hrtimer_init(&idle_cdev->timer,
> +				     CLOCK_MONOTONIC, HRTIMER_MODE_REL);
> +
> +			/*
> +			 * The wakeup function callback which is in
> +			 * charge of waking up all CPUs belonging to
> +			 * the same cluster
> +			 */
> +			idle_cdev->timer.function = cpuidle_cooling_wakeup_fn;
> +
> +			/*
> +			 * The thermal cooling device name
> +			 */
> +			snprintf(dev_name, sizeof(dev_name), "thermal-idle-%d", index++);
> +			cdev = thermal_of_cooling_device_register(np, dev_name,
> +								  idle_cdev,
> +								  &cpuidle_cooling_ops);
> +			if (IS_ERR(cdev)) {
> +				ret = PTR_ERR(cdev);
> +				goto out_fail;
> +			}
> +
> +			idle_cdev->cdev = cdev;
> +
> +			idle_cdev->cpumask = cpumask;
> +
> +			list_add(&idle_cdev->node, &cpuidle_cdev_list);
> +
> +			pr_info("Created idle cooling device for cpus '%*pbl'\n",
> +				cpumask_pr_args(cpumask));
> +		}
> +
> +		kref_get(&idle_cdev->kref);
> +
> +		/*
> +		 * Each cooling device is per package. Each package
> +		 * has a set of cpus where the physical number is
> +		 * duplicate in the kernel namespace. We need a way to
> +		 * address the waitq[] and tsk[] arrays with index
> +		 * which are not Linux cpu numbered.
> +		 *
> +		 * One solution is to use the
> +		 * topology_core_id(cpu). Other solution is to use the
> +		 * modulo.
> +		 *
> +		 * eg. 2 x cluster - 4 cores.
> +		 *
> +		 * Physical numbering -> Linux numbering -> % nr_cpus
> +		 *
> +		 * Pkg0 - Cpu0 -> 0 -> 0
> +		 * Pkg0 - Cpu1 -> 1 -> 1
> +		 * Pkg0 - Cpu2 -> 2 -> 2
> +		 * Pkg0 - Cpu3 -> 3 -> 3
> +		 *
> +		 * Pkg1 - Cpu0 -> 4 -> 0
> +		 * Pkg1 - Cpu1 -> 5 -> 1
> +		 * Pkg1 - Cpu2 -> 6 -> 2
> +		 * Pkg1 - Cpu3 -> 7 -> 3
> +		 */
> +		init_waitqueue_head(&idle_cdev->waitq[cpu % weight]);
> +
> +		tsk = kthread_create_on_cpu(cpuidle_cooling_injection_thread,
> +					    idle_cdev, cpu, "kidle_inject/%u");
> +		if (IS_ERR(tsk)) {
> +			ret = PTR_ERR(tsk);
> +			goto out_fail;
> +		}
> +
> +		idle_cdev->tsk[cpu % weight] = tsk;
> +
> +		wake_up_process(tsk);
> +	}
> +
> +	return 0;
> +
> +out_fail:
> +	list_for_each_entry(idle_cdev, &cpuidle_cdev_list, node) {
> +
> +		for_each_cpu(cpu, idle_cdev->cpumask) {
> +
> +			if (idle_cdev->tsk[cpu])
> +				kthread_stop(idle_cdev->tsk[cpu]);
> +
> +			kref_put(&idle_cdev->kref, cpuidle_cooling_release);
> +		}
> +	}
> +
> +	pr_err("Failed to create idle cooling device (%d)\n", ret);
> +
> +	return ret;
> +}

What about cpuidle_cooling_unregister() ?

> +#endif
> diff --git a/include/linux/cpu_cooling.h b/include/linux/cpu_cooling.h
> index d4292eb..2b5950b 100644
> --- a/include/linux/cpu_cooling.h
> +++ b/include/linux/cpu_cooling.h
> @@ -45,6 +45,7 @@ struct thermal_cooling_device *
>  cpufreq_power_cooling_register(struct cpufreq_policy *policy,
>  			       u32 capacitance, get_static_t plat_static_func);
>  
> +extern int cpuidle_cooling_register(void);
>  /**
>   * of_cpufreq_cooling_register - create cpufreq cooling device based on DT.
>   * @np: a valid struct device_node to the cooling device device tree node.
> @@ -118,6 +119,11 @@ void cpufreq_cooling_unregister(struct thermal_cooling_device *cdev)
>  {
>  	return;
>  }
> +
> +static inline int cpuidle_cooling_register(void)

You need to use the new macros of cpufreq and cpuidle here as well,
else you will see compile time errors with some configurations.

> +{
> +	return 0;
> +}
>  #endif	/* CONFIG_CPU_THERMAL */
>  
>  #endif /* __CPU_COOLING_H__ */
> -- 
> 2.7.4

-- 
viresh