Date: Wed, 11 Jun 2014 07:32:54 -0400
From: Eduardo Valentin <edubezval@gmail.com>
To: Javi Merino <javi.merino@arm.com>
Cc: linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org,
        punit.agrawal@arm.com, Zhang Rui <rui.zhang@intel.com>
Subject: Re: [RFC PATCH v3 4/7] thermal: introduce the Power Actor API
Message-ID: <20140611113254.GA6961@developer>
References: <1401790715-5630-1-git-send-email-javi.merino@arm.com>
 <1401790715-5630-5-git-send-email-javi.merino@arm.com>
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Hello Javi,

On Tue, Jun 03, 2014 at 11:18:32AM +0100, Javi Merino wrote:
> This patch introduces the Power Actor API in the thermal framework.
> With it, devices that can report their power consumption and control
> it can be registered.  This base interface is meant to be used to
> derive specific power actors, such as a cpu power actor.
> 
> Cc: Zhang Rui <rui.zhang@intel.com>
> Cc: Eduardo Valentin <edubezval@gmail.com>
> Signed-off-by: Javi Merino <javi.merino@arm.com>
> ---
>  Documentation/thermal/power_actor.txt     | 38 ++++++++++++++++++
>  drivers/thermal/Kconfig                   |  3 ++
>  drivers/thermal/Makefile                  |  2 +
>  drivers/thermal/power_actor/Makefile      |  5 +++
>  drivers/thermal/power_actor/power_actor.c | 64 +++++++++++++++++++++++++++++++
>  drivers/thermal/power_actor/power_actor.h | 64 +++++++++++++++++++++++++++++++

Do you think this API may have other users other than thermal?

If yes, I propose moving it somewhere else, such as driver/base/power.


>  6 files changed, 176 insertions(+)
>  create mode 100644 Documentation/thermal/power_actor.txt
>  create mode 100644 drivers/thermal/power_actor/Makefile
>  create mode 100644 drivers/thermal/power_actor/power_actor.c
>  create mode 100644 drivers/thermal/power_actor/power_actor.h
> 
> diff --git a/Documentation/thermal/power_actor.txt b/Documentation/thermal/power_actor.txt
> new file mode 100644
> index 000000000000..5a61f32ec143
> --- /dev/null
> +++ b/Documentation/thermal/power_actor.txt
> @@ -0,0 +1,38 @@
> +
> +Power Actor API
> +===============
> +
> +The base power actor API is meant to be used to derive specific power


How about having a deeper explanation? Maybe including one or two
paragraphs explaning why and when using this API makes sense.

One or two scenario explanation also would help.

An explanation of the difference to cooling API is also good to have.

> +actors, such as a cpu power actor.  When registering, they should call
> +`power_actor_register()` with a unique `enum power_actor_types`.  When

Why this enum? Maybe it is a design copy of PM QoS? But to me this is
bound to struct device, no?

> +unregistering, the power actor should call `power_actor_unregister()`
> +with the `struct power_actor *` received in the call to
> +`power_actor_register()`.
> +
> +Callbacks
> +---------
> +
> +1. u32 get_req_power(struct power_actor *actor)
> +@actor: a valid `struct power_actor *` registered with
> +        `power_actor_register()`
> +
> +`get_req_power()` returns the current requested power in milliwatts.
> +
> +2. u32 get_max_power(struct power_actor *actor)
> +@actor: a valid `struct power_actor *` registered with
> +        `power_actor_register()`
> +
> +`get_max_power()` returns the maximum power that the device could
> +consume if it was fully utilized.  It's a function as some devices'
> +maximum power consumption can change due to external factors such as
> +temperature.
> +
> +3. int set_power(struct power_actor *actor, u32 power)
> +@actor: a valid `struct power_actor *` registered with
> +        `power_actor_register()`
> +@power: power in milliwatts
> +
> +`set_power()` should configure the device to consume @power
> +milliwatts.
> +
> +Returns 0 on success, -E* on error.
> diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
> index 2d51912a6e40..47e2f15537ca 100644
> --- a/drivers/thermal/Kconfig
> +++ b/drivers/thermal/Kconfig
> @@ -89,6 +89,9 @@ config THERMAL_GOV_USER_SPACE
>  	help
>  	  Enable this to let the user space manage the platform thermals.
>  
> +config THERMAL_POWER_ACTOR
> +	bool
> +

Why empty description/help?

>  config CPU_THERMAL
>  	bool "generic cpu cooling support"
>  	depends on CPU_FREQ
> diff --git a/drivers/thermal/Makefile b/drivers/thermal/Makefile
> index 54e4ec9eb5df..878a02cab7d1 100644
> --- a/drivers/thermal/Makefile
> +++ b/drivers/thermal/Makefile
> @@ -14,6 +14,8 @@ thermal_sys-$(CONFIG_THERMAL_GOV_FAIR_SHARE)	+= fair_share.o
>  thermal_sys-$(CONFIG_THERMAL_GOV_STEP_WISE)	+= step_wise.o
>  thermal_sys-$(CONFIG_THERMAL_GOV_USER_SPACE)	+= user_space.o
>  
> +obj-$(CONFIG_THERMAL_POWER_ACTOR) += power_actor/
> +
>  # cpufreq cooling
>  thermal_sys-$(CONFIG_CPU_THERMAL)	+= cpu_cooling.o
>  
> diff --git a/drivers/thermal/power_actor/Makefile b/drivers/thermal/power_actor/Makefile
> new file mode 100644
> index 000000000000..46478f4928be
> --- /dev/null
> +++ b/drivers/thermal/power_actor/Makefile
> @@ -0,0 +1,5 @@
> +#
> +# Makefile for the power actors
> +#
> +
> +obj-y += power_actor.o

Why a new directory? Maybe using parent dir is enough?

> diff --git a/drivers/thermal/power_actor/power_actor.c b/drivers/thermal/power_actor/power_actor.c
> new file mode 100644
> index 000000000000..d891deb0e2a1
> --- /dev/null
> +++ b/drivers/thermal/power_actor/power_actor.c
> @@ -0,0 +1,64 @@
> +/*
> + * Basic interface for power actors
> + *
> + * Copyright (C) 2014 ARM Ltd.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed "as is" WITHOUT ANY WARRANTY of any
> + * kind, whether express or implied; without even the implied warranty
> + * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + */
> +
> +#define pr_fmt(fmt) "Power actor: " fmt
> +
> +#include <linux/err.h>
> +#include <linux/list.h>
> +#include <linux/slab.h>
> +
> +#include "power_actor.h"
> +
> +LIST_HEAD(actor_list);
> +
> +/**
> + * power_actor_register - Register an actor in the power actor API
> + * @type:	actor type
> + * @ops:	struct power_actor_ops for this actor
> + * @privdata:	pointer to private data related to the actor
> + *
> + * Returns the struct power_actor * on success, ERR_PTR() on failure
> + */
> +struct power_actor *power_actor_register(enum power_actor_types type,
> +					struct power_actor_ops *ops,
> +					void *privdata)
> +{
> +	struct power_actor *actor;
> +
> +	if (!ops->get_req_power || !ops->get_max_power || !ops->set_power)
> +		return ERR_PTR(-EINVAL);
> +
> +	actor = kzalloc(sizeof(*actor), GFP_KERNEL);

devm_?

> +	if (!actor)
> +		return ERR_PTR(-ENOMEM);
> +
> +	actor->type = type;
> +	actor->ops = ops;
> +	actor->data = privdata;
> +
> +	list_add(&actor->actor_node, &actor_list);
> +

Do you need to protect this one?

> +	return actor;
> +}
> +
> +/**
> + * power_actor_unregister - Unregister an actor
> + * @actor:	the actor to unregister
> + */
> +void power_actor_unregister(struct power_actor *actor)
> +{
> +	list_del(&actor->actor_node);
> +	kfree(actor);
> +}
> diff --git a/drivers/thermal/power_actor/power_actor.h b/drivers/thermal/power_actor/power_actor.h
> new file mode 100644
> index 000000000000..28098f43630b
> --- /dev/null
> +++ b/drivers/thermal/power_actor/power_actor.h
> @@ -0,0 +1,64 @@
> +/*
> + * Copyright (C) 2014 ARM Ltd.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program.  If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#ifndef __POWER_ACTOR_H__
> +#define __POWER_ACTOR_H__
> +
> +#include <linux/list.h>
> +
> +#define MAX_NUM_ACTORS 8
> +

unused define

> +enum power_actor_types {
> +};

I still don't get this enum.

> +
> +struct power_actor;
> +
> +/**
> + * struct power_actor_ops - callbacks for power actors
> + * @get_req_power:	return the current requested power in milliwatts
> + * @get_max_power:	return the max power that the device can currently
> + *			consume in milliwatts
> + * @set_power:		configure the device to consume a certain power in
> + *			milliwatts
> + */
> +struct power_actor_ops {
> +	u32 (*get_req_power)(struct power_actor *);
> +	u32 (*get_max_power)(struct power_actor *);
> +	int (*set_power)(struct power_actor *, u32);
> +};
> +
> +/**
> + * struct power_actor - structure for a power actor
> + * @type:	the type of power actor.
> + * @ops:	callbacks for the power actor
> + * @data:	a private pointer for type-specific data
> + * @actor_node:	node in actor_list
> + */
> +struct power_actor {
> +	enum power_actor_types type;
> +	struct power_actor_ops *ops;
> +	void *data;
> +	struct list_head actor_node;
> +};
> +
> +struct power_actor *power_actor_register(enum power_actor_types type,
> +					struct power_actor_ops *ops,
> +					void *privdata);
> +void power_actor_unregister(struct power_actor *actor);
> +
> +extern struct list_head actor_list;
> +
> +#endif /* __POWER_ACTOR_H__ */
> -- 
> 1.9.1
> 
> 
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