Re: [RFC Disable suspend on a specific device] This is a little change in linux power scheme

[Michael Trimarchi <trimarchi@gandalf.sssup.it>]

Rafael J. Wysocki wrote:
> On Tuesday 07 April 2009, Michael Trimarchi wrote:
>   
>> Hi,
>>
>> Rafael J. Wysocki wrote:
>>     
>>> On Tuesday 07 April 2009, Michael Trimarchi wrote:
>>>   
>>>       
>>>> This is a little rework of linux power scheme. TODO:
>>>> - remove recursive call
>>>> - clean-up code
>>>>
>>>> Avoid suspend of a device that is connected with other coprocessor
>>>> like GSM chip.
>>>>     
>>>>         
>>> Well, can you please tell us a bit about the motivation for this work?
>>>
>>> I don't like the approach, but I'd like to know what you're trying to achieve.
>>>   
>>>       
>> I works on an hardware that have the gsm connect to wm8753 and the 
>> bluetooth subsystem
>> too direct connected. So I would like that a phone call for example 
>> remains on during
>> system suspend. With this approch I can disable suspend of an entire 
>> subtree of device,
>> that can be used by other hardware component. This change avoid any 
>> specific change to the
>> driver.
>>     
>
> Why do you want to avoid changing the driver, actually?
>
> Rafael
>
>   
Because, the driver may be connected to other device and you must change 
the entire
set. This simple modification can help to share devices on an embedded 
board and control
suspend/resume enable from user space. I don't know if it can be usefull 
on broken board/device too. Do you see any possible risk with this 
change? When I write it I try to have a simple
modification on linux-pm part.

Michael
>    
>   
>>>> Signed-off-by: Michael Trimarchi <trimarchi@gandalf.sssup.it>
>>>>
>>>> ---
>>>> diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
>>>> index 3098c46..2a6ddb3 100644
>>>> --- a/drivers/base/power/main.c
>>>> +++ b/drivers/base/power/main.c
>>>> @@ -63,6 +63,40 @@ void device_pm_unlock(void)
>>>>  	mutex_unlock(&dpm_list_mtx);
>>>>  }
>>>>  
>>>> +int device_set_may_suspend_enable(struct device *dev, void *data)
>>>> +{
>>>> +	/* if the device is suspend the subtree is in may_suspend status */
>>>> +	if (!dev->power.can_suspend)
>>>> +		goto out;
>>>> +
>>>> +	dev->power.may_suspend = (unsigned int)data;
>>>> +	device_for_each_child(dev, data,
>>>> +			      device_set_may_suspend_enable);
>>>> +out:
>>>> +	return 0;
>>>> +}
>>>> +
>>>> +/**
>>>> + *	device_set_suspend_enable - enable/disable device to suspend
>>>> + */
>>>> +int device_set_suspend_enable(struct device *dev, int enable)
>>>> +{
>>>> +	mutex_lock(&dpm_list_mtx);
>>>> +
>>>> +	if (dev->power.can_suspend == !!enable)
>>>> +		goto out;
>>>> +
>>>> +	/* Update device children to avoid suspend */
>>>> +	device_for_each_child(dev, (void *)!!enable,
>>>> +			      device_set_may_suspend_enable);
>>>> +
>>>> +	dev->power.can_suspend = !!enable;
>>>> +out:
>>>> +	mutex_unlock(&dpm_list_mtx);
>>>> +	return 0;
>>>> +}
>>>> +EXPORT_SYMBOL_GPL(device_set_suspend_enable);
>>>> +
>>>>  /**
>>>>   *	device_pm_add - add a device to the list of active devices
>>>>   *	@dev:	Device to be added to the list
>>>> @@ -77,6 +111,13 @@ void device_pm_add(struct device *dev)
>>>>  		if (dev->parent->power.status >= DPM_SUSPENDING)
>>>>  			dev_warn(dev, "parent %s should not be sleeping\n",
>>>>  				 dev_name(dev->parent));
>>>> +		if (!device_can_suspend(dev->parent)) {
>>>> +			mutex_unlock(&dpm_list_mtx);
>>>> +			/* if the parent has suspend disable, propagate it
>>>> +			 * to the new child */
>>>> +			device_set_may_suspend_enable(dev, 0);
>>>> +			mutex_lock(&dpm_list_mtx);
>>>> +		}
>>>>  	} else if (transition_started) {
>>>>  		/*
>>>>  		 * We refuse to register parentless devices while a PM
>>>> @@ -120,13 +161,13 @@ static int pm_op(struct device *dev, struct dev_pm_ops *ops,
>>>>  	switch (state.event) {
>>>>  #ifdef CONFIG_SUSPEND
>>>>  	case PM_EVENT_SUSPEND:
>>>> -		if (ops->suspend) {
>>>> +		if (device_can_suspend(dev) && ops->suspend) {
>>>>  			error = ops->suspend(dev);
>>>>  			suspend_report_result(ops->suspend, error);
>>>>  		}
>>>>  		break;
>>>>  	case PM_EVENT_RESUME:
>>>> -		if (ops->resume) {
>>>> +		if (device_can_suspend(dev) && ops->resume) {
>>>>  			error = ops->resume(dev);
>>>>  			suspend_report_result(ops->resume, error);
>>>>  		}
>>>> diff --git a/drivers/base/power/power.h b/drivers/base/power/power.h
>>>> index 41f51fa..1197b13 100644
>>>> --- a/drivers/base/power/power.h
>>>> +++ b/drivers/base/power/power.h
>>>> @@ -1,6 +1,13 @@
>>>>  static inline void device_pm_init(struct device *dev)
>>>>  {
>>>>  	dev->power.status = DPM_ON;
>>>> +	dev->power.can_suspend = 1;
>>>> +	dev->power.may_suspend = 1;
>>>> +}
>>>> +
>>>> +static inline int device_can_suspend(struct device *dev)
>>>> +{
>>>> +	return (dev->power.can_suspend && dev->power.may_suspend);
>>>>  }
>>>>  
>>>>  #ifdef CONFIG_PM_SLEEP
>>>> diff --git a/drivers/base/power/sysfs.c b/drivers/base/power/sysfs.c
>>>> index 596aeec..25236aa 100644
>>>> --- a/drivers/base/power/sysfs.c
>>>> +++ b/drivers/base/power/sysfs.c
>>>> @@ -43,6 +43,34 @@
>>>>  static const char enabled[] = "enabled";
>>>>  static const char disabled[] = "disabled";
>>>>  
>>>> +static ssize_t suspend_show(struct device *dev, struct device_attribute *attr,
>>>> +				char *buf)
>>>> +{
>>>> +	return sprintf(buf, "%s\n", device_can_suspend(dev)
>>>> +		? enabled : disabled);
>>>> +}
>>>> +
>>>> +static ssize_t
>>>> +suspend_store(struct device *dev, struct device_attribute *attr,
>>>> +		const char *buf, size_t n)
>>>> +{
>>>> +	char *cp;
>>>> +	int len = n;
>>>> +
>>>> +	cp = memchr(buf, '\n', n);
>>>> +	if (cp)
>>>> +		len = cp - buf;
>>>> +	if (len == sizeof enabled - 1
>>>> +			&& strncmp(buf, enabled, sizeof enabled - 1) == 0)
>>>> +		device_set_suspend_enable(dev, 1);
>>>> +	else if (len == sizeof disabled - 1
>>>> +			&& strncmp(buf, disabled, sizeof disabled - 1) == 0)
>>>> +		device_set_suspend_enable(dev, 0);
>>>> +	else
>>>> +		return -EINVAL;
>>>> +	return n;
>>>> +}
>>>> +
>>>>  static ssize_t
>>>>  wake_show(struct device * dev, struct device_attribute *attr, char * buf)
>>>>  {
>>>> @@ -76,10 +104,11 @@ wake_store(struct device * dev, struct device_attribute *attr,
>>>>  }
>>>>  
>>>>  static DEVICE_ATTR(wakeup, 0644, wake_show, wake_store);
>>>> -
>>>> +static DEVICE_ATTR(suspend, 0644, suspend_show, suspend_store);
>>>>  
>>>>  static struct attribute * power_attrs[] = {
>>>>  	&dev_attr_wakeup.attr,
>>>> +	&dev_attr_suspend.attr,
>>>>  	NULL,
>>>>  };
>>>>  static struct attribute_group pm_attr_group = {
>>>> diff --git a/include/linux/device.h b/include/linux/device.h
>>>> index fdb073b..dc9f242 100644
>>>> --- a/include/linux/device.h
>>>> +++ b/include/linux/device.h
>>>> @@ -487,6 +487,7 @@ extern struct device *device_find_child(struct device *dev, void *data,
>>>>  				int (*match)(struct device *dev, void *data));
>>>>  extern int device_rename(struct device *dev, char *new_name);
>>>>  extern int device_move(struct device *dev, struct device *new_parent);
>>>> +extern int device_set_suspend_enable(struct device *dev, int enable);
>>>>  
>>>>  /*
>>>>   * Root device objects for grouping under /sys/devices
>>>> diff --git a/include/linux/pm.h b/include/linux/pm.h
>>>> index de2e0a8..7586a90 100644
>>>> --- a/include/linux/pm.h
>>>> +++ b/include/linux/pm.h
>>>> @@ -319,6 +319,9 @@ struct dev_pm_info {
>>>>  	pm_message_t		power_state;
>>>>  	unsigned		can_wakeup:1;
>>>>  	unsigned		should_wakeup:1;
>>>> +	unsigned		can_suspend:1;
>>>> +	unsigned		may_suspend:1;
>>>> +
>>>>  	enum dpm_state		status;		/* Owned by the PM core */
>>>>  #ifdef	CONFIG_PM_SLEEP
>>>>  	struct list_head	entry;
>>>>         
>
>