Message-id: <1418204220.16644.14.camel@AMDC1943>
Date:	Wed, 10 Dec 2014 10:37:00 +0100
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Chanwoo Choi <cw00.choi@...sung.com>
Cc:	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	myungjoo.ham@...sung.com, kyungmin.park@...sung.com,
	kgene.kim@...sung.com, rafael.j.wysocki@...el.com,
	a.kesavan@...sung.com, tomasz.figa@...il.com,
	b.zolnierkie@...sung.com, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org
Subject: Re: [RFC PATCHv2 1/7] devfreq: event: Add new devfreq_event class to
 provide basic data for devfreq governor

On wto, 2014-12-09 at 23:13 +0900, Chanwoo Choi wrote:
> This patch add new devfreq_event class for devfreq_event device which provide
> raw data (e.g., memory bus utilization/GPU utilization). This raw data from
> devfreq_event data would be used for the governor of devfreq subsystem.
> - devfreq_event device : Provide raw data for governor of existing devfreq device
> - devfreq device       : Monitor device state and change frequency/voltage of device
>                          using the raw data from devfreq_event device
> 
> The devfreq subsystem support generic DVFS(Dynamic Voltage/Frequency Scaling)
> for Non-CPU Devices. The devfreq device would dertermine current device state
> using various governor (e.g., ondemand, performance, powersave). After completed
> determination of system state, devfreq device would change the frequency/voltage
> of devfreq device according to the result of governor.
> 
> But, devfreq governor must need basic data which indicates current device state.
> Existing devfreq subsystem only consider devfreq device which check current system
> state and determine proper system state using basic data. There is no subsystem
> for device providing basic data to devfreq device.
> 
> The devfreq subsystem must need devfreq_event device(data-provider device) for
> existing devfreq device. So, this patch add new devfreq_event class for
> devfreq_event device which read various basic data(e.g, memory bus utilization,
> GPU utilization) and provide measured data to existing devfreq device through
> standard APIs of devfreq_event class.
> 
> The following description explains the feature of two kind of devfreq class:
> - devfreq class (existing)
>  : devfreq consumer device use raw data from devfreq_event device for
>    determining proper current system state and change voltage/frequency
>    dynamically using various governors.
> 
> - devfreq_event class (new)
>  : Provide measured raw data to devfreq device for governor
> 
> Cc: MyungJoo Ham <myungjoo.ham@...sung.com>
> Cc: Kyungmin Park <kyungmin.park@...sung.com>
> Signed-off-by: Chanwoo Choi <cw00.choi@...sung.com>
> ---
>  drivers/devfreq/Kconfig         |   2 +
>  drivers/devfreq/Makefile        |   5 +-
>  drivers/devfreq/devfreq-event.c | 302 ++++++++++++++++++++++++++++++++++++++++
>  drivers/devfreq/event/Makefile  |   1 +
>  include/linux/devfreq.h         | 141 +++++++++++++++++++
>  5 files changed, 450 insertions(+), 1 deletion(-)
>  create mode 100644 drivers/devfreq/devfreq-event.c
>  create mode 100644 drivers/devfreq/event/Makefile
> 
> diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
> index faf4e70..4d15b62 100644
> --- a/drivers/devfreq/Kconfig
> +++ b/drivers/devfreq/Kconfig
> @@ -87,4 +87,6 @@ config ARM_EXYNOS5_BUS_DEVFREQ
>  	  It reads PPMU counters of memory controllers and adjusts the
>  	  operating frequencies and voltages with OPP support.
>  
> +comment "DEVFREQ Event Drivers"
> +
>  endif # PM_DEVFREQ
> diff --git a/drivers/devfreq/Makefile b/drivers/devfreq/Makefile
> index 16138c9..a1ffabe 100644
> --- a/drivers/devfreq/Makefile
> +++ b/drivers/devfreq/Makefile
> @@ -1,4 +1,4 @@
> -obj-$(CONFIG_PM_DEVFREQ)	+= devfreq.o
> +obj-$(CONFIG_PM_DEVFREQ)		+= devfreq.o devfreq-event.o
>  obj-$(CONFIG_DEVFREQ_GOV_SIMPLE_ONDEMAND)	+= governor_simpleondemand.o
>  obj-$(CONFIG_DEVFREQ_GOV_PERFORMANCE)	+= governor_performance.o
>  obj-$(CONFIG_DEVFREQ_GOV_POWERSAVE)	+= governor_powersave.o
> @@ -7,3 +7,6 @@ obj-$(CONFIG_DEVFREQ_GOV_USERSPACE)	+= governor_userspace.o
>  # DEVFREQ Drivers
>  obj-$(CONFIG_ARM_EXYNOS4_BUS_DEVFREQ)	+= exynos/
>  obj-$(CONFIG_ARM_EXYNOS5_BUS_DEVFREQ)	+= exynos/
> +
> +# DEVFREQ Event Drivers
> +obj-$(CONFIG_PM_DEVFREQ)		+= event/
> diff --git a/drivers/devfreq/devfreq-event.c b/drivers/devfreq/devfreq-event.c
> new file mode 100644
> index 0000000..b47329f
> --- /dev/null
> +++ b/drivers/devfreq/devfreq-event.c
> @@ -0,0 +1,302 @@
> +/*
> + * devfreq-event: Generic DEVFREQ Event class driver
> + *
> + * Copyright (C) 2014 Samsung Electronics
> + * Chanwoo Choi <cw00.choi@...sung.com>
> + *
> + * 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 driver is based on drivers/devfreq/devfreq.c
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/sched.h>
> +#include <linux/errno.h>
> +#include <linux/err.h>
> +#include <linux/init.h>
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +#include <linux/stat.h>
> +#include <linux/pm_opp.h>
> +#include <linux/devfreq.h>
> +#include <linux/workqueue.h>
> +#include <linux/platform_device.h>
> +#include <linux/list.h>
> +#include <linux/printk.h>
> +#include <linux/hrtimer.h>
> +#include <linux/of.h>
> +#include "governor.h"
> +
> +static struct class *devfreq_event_class;
> +
> +/* The list of all devfreq event list */
> +static LIST_HEAD(devfreq_event_list);
> +static DEFINE_MUTEX(devfreq_event_list_lock);
> +
> +#define to_devfreq_event(DEV) container_of(DEV, struct devfreq_event_dev, dev)
> +
> +struct devfreq_event_dev *devfreq_add_event_device(struct device *dev,
> +					struct devfreq_event_desc *desc)
> +{
> +	struct devfreq_event_dev *event_dev;
> +	static atomic_t event_no = ATOMIC_INIT(0);
> +	int ret;
> +
> +	if (!dev || !desc)
> +		return ERR_PTR(-EINVAL);
> +
> +	if (!desc->name || !desc->ops)
> +		return ERR_PTR(-EINVAL);
> +
> +	event_dev = kzalloc(sizeof(struct devfreq_event_dev), GFP_KERNEL);
> +	if (!event_dev)
> +		return ERR_PTR(-ENOMEM);

Is this memory freed anywhere when driver is removed? I couldn't find
it. I couldn't also find function like devfreq_remove_event_device()
which would be reverting all the work done when adding.

> +
> +	mutex_lock(&devfreq_event_list_lock);
> +
> +	mutex_init(&event_dev->lock);
> +	event_dev->desc = desc;
> +	event_dev->dev.parent = dev;
> +	event_dev->dev.class = devfreq_event_class;
> +
> +	dev_set_name(&event_dev->dev, "event.%d",
> +		     atomic_inc_return(&event_no) - 1);
> +	ret = device_register(&event_dev->dev);
> +	if (ret != 0) {
> +		put_device(&event_dev->dev);
> +		goto err;
> +	}
> +	dev_set_drvdata(&event_dev->dev, event_dev);
> +
> +	/* Add devfreq event device to devfreq_event_list */
> +	INIT_LIST_HEAD(&event_dev->node);
> +	list_add(&event_dev->node, &devfreq_event_list);
> +
> +	mutex_unlock(&devfreq_event_list_lock);
> +
> +	return event_dev;
> +err:

Missing 'mutex_unlock(&devfreq_event_list_lock)' here.


> +	kfree(event_dev);
> +	return ERR_PTR(ret);
> +}
> +EXPORT_SYMBOL(devfreq_add_event_device);
> +
> +struct devfreq_event_dev *devfreq_get_event_dev(const char *event_dev_name)
> +{
> +	struct devfreq_event_dev *event_dev;
> +
> +	mutex_lock(&devfreq_event_list_lock);
> +	list_for_each_entry(event_dev, &devfreq_event_list, node) {
> +		if (!strcmp(event_dev->desc->name, event_dev_name))
> +			goto out;
> +	}
> +	event_dev = NULL;
> +out:
> +	mutex_unlock(&devfreq_event_list_lock);
> +
> +	return event_dev;
> +}
> +EXPORT_SYMBOL_GPL(devfreq_get_event_dev);
> +
> +struct devfreq_event_dev *devfreq_get_event_dev_by_phandle(struct device *dev,
> +						      int index)
> +{
> +	struct device_node *node;
> +	struct devfreq_event_dev *event_dev;
> +
> +	if (!dev->of_node) {
> +		dev_err(dev, "device does not have a device node entry\n");
> +		return ERR_PTR(-EINVAL);
> +	}
> +
> +	node = of_parse_phandle(dev->of_node, "devfreq-events", index);
> +	if (!node) {
> +		dev_err(dev, "failed to get phandle in %s node\n",
> +			dev->of_node->full_name);
> +		return ERR_PTR(-ENODEV);
> +	}
> +
> +	event_dev = devfreq_get_event_dev(node->name);
> +	if (!event_dev) {
> +		dev_err(dev, "unable to get devfreq-event device : %s\n",
> +			node->name);

of_node_put() for node obtained with of_parse_phandle().

> +		return ERR_PTR(-ENODEV);
> +	}
> +
> +	return event_dev;
> +}
> +EXPORT_SYMBOL_GPL(devfreq_get_event_dev_by_phandle);
> +
> +int devfreq_put_event_dev(struct devfreq_event_dev *event_dev)
> +{

of_node_put() here to decrement refcnt from of_parse_phandle()?

> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(devfreq_put_event_dev);
> +
> +int devfreq_enable_event_dev(struct devfreq_event_dev *event_dev)
> +{
> +	int ret = 0;
> +
> +	if (!event_dev || !event_dev->desc)
> +		return -EINVAL;
> +
> +	mutex_lock(&event_dev->lock);
> +	if (event_dev->desc->ops && event_dev->desc->ops->enable) {
> +		ret = event_dev->desc->ops->enable(event_dev);
> +		if (ret < 0)
> +			goto err;
> +	}
> +	event_dev->enable_count++;
> +err:
> +	mutex_unlock(&event_dev->lock);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(devfreq_enable_event_dev);
> +
> +int devfreq_disable_event_dev(struct devfreq_event_dev *event_dev)
> +{
> +	int ret = 0;
> +
> +	if (!event_dev || !event_dev->desc)
> +		return -EINVAL;
> +
> +	mutex_lock(&event_dev->lock);
> +	if (event_dev->enable_count > 0) {
> +		event_dev->enable_count--;
> +	} else {
> +		dev_warn(&event_dev->dev, "unbalanced enable_count\n");
> +		ret = -EINVAL;
> +		goto err;
> +	}
> +
> +	if (event_dev->desc->ops && event_dev->desc->ops->disable) {
> +		ret = event_dev->desc->ops->disable(event_dev);
> +		if (ret < 0) {
> +			event_dev->enable_count++;
> +			goto err;
> +		}
> +	}
> +err:
> +	mutex_unlock(&event_dev->lock);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(devfreq_disable_event_dev);
> +
> +bool devfreq_is_enabled_event_dev(struct devfreq_event_dev *event_dev)
> +{
> +	bool enabled = false;
> +
> +	if (!event_dev || !event_dev->desc)
> +		return enabled;
> +
> +	if (!(event_dev->enable_count > 0))
> +		return enabled;
> +
> +	if (event_dev->desc->ops && event_dev->desc->ops->is_enabled)
> +		enabled = event_dev->desc->ops->is_enabled(event_dev);
> +
> +	return enabled;
> +}
> +EXPORT_SYMBOL_GPL(devfreq_is_enabled_event_dev);
> +
> +int devfreq_set_event_event_dev(struct devfreq_event_dev *event_dev)

The convention of names you use is not obvious to me. I would expect
rather devfreq_event_dev_XXX (where XXX is "set_event", "is_enabled"
etc).
The one above is good example what is the issue with current convention:
devfreq_set_event_event_dev
            ^     ^
This double "event" looks weird.

> +{
> +	if (!event_dev || !event_dev->desc)
> +		return -EINVAL;
> +
> +	if (!devfreq_is_enabled_event_dev(event_dev))
> +		return -EPERM;
> +
> +	if (event_dev->desc->ops && event_dev->desc->ops->set_event)
> +		return event_dev->desc->ops->set_event(event_dev);

No mutexes here? What exactly is protected by mutex?

> +
> +	return -EINVAL;
> +}
> +EXPORT_SYMBOL_GPL(devfreq_set_event_event_dev);
> +
> +int devfreq_get_event_event_dev(struct devfreq_event_dev *event_dev,
> +				int *total_event)
> +{
> +	if (!event_dev || !event_dev->desc)
> +		return -EINVAL;
> +
> +	if (!devfreq_is_enabled_event_dev(event_dev))
> +		return -EPERM;
> +
> +	if (event_dev->desc->ops && event_dev->desc->ops->get_event)
> +		return event_dev->desc->ops->get_event(event_dev, total_event);
> +
> +	return -EINVAL;
> +}
> +EXPORT_SYMBOL_GPL(devfreq_get_event_event_dev);
> +
> +int devfreq_reset_event_dev(struct devfreq_event_dev *event_dev)
> +{
> +	if (!event_dev || !event_dev->desc)
> +		return -EINVAL;
> +
> +	if (!devfreq_is_enabled_event_dev(event_dev))
> +		return -EPERM;
> +
> +	if (event_dev->desc->ops && event_dev->desc->ops->reset)
> +		return event_dev->desc->ops->reset(event_dev);

Same here, no mutex?
> +
> +	return -EINVAL;
> +}
> +EXPORT_SYMBOL_GPL(devfreq_reset_event_dev);
> +
> +void *event_dev_get_drvdata(struct devfreq_event_dev *event_dev)
> +{
> +	return event_dev->desc->driver_data;
> +}
> +EXPORT_SYMBOL_GPL(event_dev_get_drvdata);

Best regards,
Krzysztof


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