linux-kernel - Re: [RFT][PATCH 1/3] PM: QoS: Introduce frequency QoS

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Date:   Thu, 24 Oct 2019 19:01:06 +0000
From:   Leonard Crestez <leonard.crestez@....com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Viresh Kumar <viresh.kumar@...aro.org>
CC:     Linux PM <linux-pm@...r.kernel.org>,
        Linux ACPI <linux-acpi@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Dmitry Osipenko <digetx@...il.com>
Subject: Re: [RFT][PATCH 1/3] PM: QoS: Introduce frequency QoS

On 16.10.2019 13:48, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Introduce frequency QoS, based on the "raw" low-level PM QoS, to
> represent min and max frequency requests and aggregate constraints.
> 
> The min and max frequency requests are to be represented by
> struct freq_qos_request objects and the aggregate constraints are to
> be represented by struct freq_constraints objects.  The latter are
> expected to be initialized with the help of freq_constraints_init().
> 
> The freq_qos_read_value() helper is defined to retrieve the aggregate
> constraints values from a given struct freq_constraints object and
> there are the freq_qos_add_request(), freq_qos_update_request() and
> freq_qos_remove_request() helpers to manipulate the min and max
> frequency requests.  It is assumed that the the helpers will not
> run concurrently with each other for the same struct freq_qos_request
> object, so if that may be the case, their uses must ensure proper
> synchronization between them (e.g. through locking).
> 
> In addition, freq_qos_add_notifier() and freq_qos_remove_notifier()
> are provided to add and remove notifiers that will trigger on aggregate
> constraint changes to and from a given struct freq_constraints object,
> respectively.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>   include/linux/pm_qos.h |   44 ++++++++
>   kernel/power/qos.c     |  240 +++++++++++++++++++++++++++++++++++++++++++++++++
>   2 files changed, 284 insertions(+)
> 
> Index: linux-pm/include/linux/pm_qos.h
> ===================================================================
> --- linux-pm.orig/include/linux/pm_qos.h
> +++ linux-pm/include/linux/pm_qos.h
> @@ -267,4 +267,48 @@ static inline s32 dev_pm_qos_raw_resume_
>   }
>   #endif
>   
> +#define FREQ_QOS_MIN_DEFAULT_VALUE	0
> +#define FREQ_QOS_MAX_DEFAULT_VALUE	(-1)
> +
> +enum freq_qos_req_type {
> +	FREQ_QOS_MIN = 1,
> +	FREQ_QOS_MAX,
> +};
> +
> +struct freq_constraints {
> +	struct pm_qos_constraints min_freq;
> +	struct blocking_notifier_head min_freq_notifiers;
> +	struct pm_qos_constraints max_freq;
> +	struct blocking_notifier_head max_freq_notifiers;

These min/max_freq_notifiers fields seem unused? They're initialized but 
the freq_qos_add/remove_notifier calls use min/max_freq.notifiers directly.

Should probably just be dropped.

> +/**
> + * freq_qos_add_notifier - Add frequency QoS change notifier.
> + * @qos: List of requests to add the notifier to.
> + * @type: Request type.
> + * @notifier: Notifier block to add.
> + */
> +int freq_qos_add_notifier(struct freq_constraints *qos,
> +			  enum freq_qos_req_type type,
> +			  struct notifier_block *notifier)
> +{
> +	int ret;
> +
> +	if (IS_ERR_OR_NULL(qos) || !notifier)
> +		return -EINVAL;
> +
> +	switch (type) {
> +	case FREQ_QOS_MIN:
> +		ret = blocking_notifier_chain_register(qos->min_freq.notifiers,
> +						       notifier);
> +		break;
> +	case FREQ_QOS_MAX:
> +		ret = blocking_notifier_chain_register(qos->max_freq.notifiers,
> +						       notifier);
> +		break;
> +	default:
> +		WARN_ON(1);
> +		ret = -EINVAL;
> +	}
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(freq_qos_add_notifier);
> +
> +/**
> + * freq_qos_remove_notifier - Remove frequency QoS change notifier.
> + * @qos: List of requests to remove the notifier from.
> + * @type: Request type.
> + * @notifier: Notifier block to remove.
> + */
> +int freq_qos_remove_notifier(struct freq_constraints *qos,
> +			     enum freq_qos_req_type type,
> +			     struct notifier_block *notifier)
> +{
> +	int ret;
> +
> +	if (IS_ERR_OR_NULL(qos) || !notifier)
> +		return -EINVAL;
> +
> +	switch (type) {
> +	case FREQ_QOS_MIN:
> +		ret = blocking_notifier_chain_unregister(qos->min_freq.notifiers,
> +							 notifier);
> +		break;
> +	case FREQ_QOS_MAX:
> +		ret = blocking_notifier_chain_unregister(qos->max_freq.notifiers,
> +							 notifier);
> +		break;
> +	default:
> +		WARN_ON(1);
> +		ret = -EINVAL;
> +	}
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(freq_qos_remove_notifier);