linux-kernel - Re: [PATCH v10 2/2] cpufreq: powernv: Add sysfs attributes to show throttle stats

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Date:	Mon, 29 Feb 2016 12:09:17 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	rjw@...ysocki.net,
	Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com>
Cc:	linuxppc-dev@...abs.org, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org, ego@...ux.vnet.ibm.com,
	shreyas@...ux.vnet.ibm.com, linux-api@...r.kernel.org
Subject: Re: [PATCH v10 2/2] cpufreq: powernv: Add sysfs attributes to show
 throttle stats

On 26-02-16, 16:06, Shilpasri G Bhat wrote:
> +static int powernv_cpufreq_policy_notifier(struct notifier_block *nb,
> +					   unsigned long action, void *data)
> +{
> +	struct cpufreq_policy *policy = data;
> +	int ret;
> +
> +	if (action == CPUFREQ_CREATE_POLICY) {
> +		ret = sysfs_create_group(&policy->kobj, &throttle_attr_grp);
> +		if (ret)
> +			pr_info("Failed to create throttle stats directory for cpu %d\n",
> +				policy->cpu);
> +	} else if (action == CPUFREQ_REMOVE_POLICY) {
> +		sysfs_remove_group(&policy->kobj, &throttle_attr_grp);
> +	}
> +
> +	return NOTIFY_DONE;
> +}
> +
> +static struct notifier_block powernv_cpufreq_policy_nb = {
> +	.notifier_call	= powernv_cpufreq_policy_notifier,
> +	.next		= NULL,
> +};
> +
>  static void powernv_cpufreq_stop_cpu(struct cpufreq_policy *policy)
>  {
>  	struct powernv_smp_call_data freq_data;
> @@ -603,6 +708,8 @@ static inline void clean_chip_info(void)
>  
>  static inline void unregister_all_notifiers(void)
>  {
> +	cpufreq_unregister_notifier(&powernv_cpufreq_policy_nb,
> +				    CPUFREQ_POLICY_NOTIFIER);
>  	opal_message_notifier_unregister(OPAL_MSG_OCC,
>  					 &powernv_cpufreq_opal_nb);
>  	unregister_reboot_notifier(&powernv_cpufreq_reboot_nb);
> @@ -628,6 +735,8 @@ static int __init powernv_cpufreq_init(void)
>  
>  	register_reboot_notifier(&powernv_cpufreq_reboot_nb);
>  	opal_message_notifier_register(OPAL_MSG_OCC, &powernv_cpufreq_opal_nb);
> +	cpufreq_register_notifier(&powernv_cpufreq_policy_nb,
> +				  CPUFREQ_POLICY_NOTIFIER);
>  
>  	rc = cpufreq_register_driver(&powernv_cpufreq_driver);
>  	if (!rc)

@Rafael: This driver needs to do this *ugly* notifier hack, just because we
aren't doing kobject_add() for policy->kobj before ->init(). And we did that
because, we wanted to create the policyX structure with the first CPU in
policy->related_cpus mask and related_cpus mask isn't available until we call
->init()..

Should we do something in core to make this easier for this driver?

-- 
viresh