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

["Rafael J. Wysocki" <rjw@sisk.pl>]

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.

Rafael


> 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;