Re: [RFC PATCHv2 1/7] devfreq: event: Add new devfreq_event class to provide basic data for devfreq governor

[Chanwoo Choi]

Hi Krzysztof,

I replied again this mail because I'll use the mutex for set_event()/get_event()
according to your comment. But, of_parse_phandle() seems that this function
don't need the of_node_put() function.


On 12/11/2014 11:13 AM, Chanwoo Choi wrote:
> Hi Krzysztof,
> 
> First of all, thanks for your review.
> 
> On 12/10/2014 06:37 PM, Krzysztof Kozlowski wrote:
>> 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@xxxxxxxxxxx>
>>> Cc: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
>>> Signed-off-by: Chanwoo Choi <cw00.choi@xxxxxxxxxxx>
>>> ---
>>>  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@xxxxxxxxxxx>
>>> + *
>>> + * 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.
> 
> You're right. I'll use devm_kzalloc instead of kzalloc.
> 
>>
>>> +
>>> +	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.
> 
> OK. I'll fix it.
> 
>>
>>
>>> +	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().
> 
> OK. I'll add it.

of_parse_phandle() seems that it don't need of_node_put().

> 
>>
>>> +		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()?
> 
> It is my mistake. I think that devfreq_put_event_dev is not necesssary.
> I'll remove it.
> 
>>
>>> +	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.
> 
> You're right. I'll have to fix the function name according to your comment.
> 
>>
>>> +{
>>> +	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?
> 
> I used the mutex when devfreq-event class read/write the data of devfreq_event_dev structure.

I'll use mutex for set_event() function according to your comment.

> 
>>
>>> +
>>> +	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?
> 
> I replied it on previous your question.

I'll use mutex for set_event() function according to your comment.

Best Regards,
Chanwoo Choi
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