Re: [PATCH 06/15] PM QoS: implement the per-device PM QoS constraints

[mark gross <markgross@thegnar.org>]

On Thu, Aug 11, 2011 at 05:06:43PM +0200, jean.pihet@newoldbits.com wrote:
> From: Jean Pihet <j-pihet@ti.com>
> 
> Implement the per-device PM QoS constraints by creating a device
> PM QoS API, which calls the PM QoS constraints management core code.
> 
> The per-device latency constraints data strctures are stored
> in the device dev_pm_info struct.
> 
> The device PM code calls the init and destroy of the per-device constraints
> data struct in order to support the dynamic insertion and removal of the
> devices in the system.
> 
> To minimize the data usage by the per-device constraints, the data struct
> is only allocated at the first call to dev_pm_qos_add_request.
> The data is later free'd when the device is removed from the system.
> 
> Signed-off-by: Jean Pihet <j-pihet@ti.com>
> ---
>  drivers/base/power/Makefile |    4 +-
>  drivers/base/power/main.c   |    3 +
>  drivers/base/power/qos.c    |  262 +++++++++++++++++++++++++++++++++++++++++++
>  include/linux/pm.h          |    9 ++
>  include/linux/pm_qos.h      |   39 +++++++
>  5 files changed, 315 insertions(+), 2 deletions(-)
>  create mode 100644 drivers/base/power/qos.c
> 
> diff --git a/drivers/base/power/Makefile b/drivers/base/power/Makefile
> index 3647e11..1a61f89 100644
> --- a/drivers/base/power/Makefile
> +++ b/drivers/base/power/Makefile
> @@ -1,8 +1,8 @@
> -obj-$(CONFIG_PM)	+= sysfs.o generic_ops.o
> +obj-$(CONFIG_PM)	+= sysfs.o generic_ops.o qos.o
>  obj-$(CONFIG_PM_SLEEP)	+= main.o wakeup.o
>  obj-$(CONFIG_PM_RUNTIME)	+= runtime.o
>  obj-$(CONFIG_PM_TRACE_RTC)	+= trace.o
>  obj-$(CONFIG_PM_OPP)	+= opp.o
>  obj-$(CONFIG_HAVE_CLK)	+= clock_ops.o
>  
> -ccflags-$(CONFIG_DEBUG_DRIVER) := -DDEBUG
> \ No newline at end of file
> +ccflags-$(CONFIG_DEBUG_DRIVER) := -DDEBUG
> diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
> index 06f09bf..f5c0e0e 100644
> --- a/drivers/base/power/main.c
> +++ b/drivers/base/power/main.c
> @@ -22,6 +22,7 @@
>  #include <linux/mutex.h>
>  #include <linux/pm.h>
>  #include <linux/pm_runtime.h>
> +#include <linux/pm_qos.h>
>  #include <linux/resume-trace.h>
>  #include <linux/interrupt.h>
>  #include <linux/sched.h>
> @@ -97,6 +98,7 @@ void device_pm_add(struct device *dev)
>  			dev_name(dev->parent));
>  	list_add_tail(&dev->power.entry, &dpm_list);
>  	mutex_unlock(&dpm_list_mtx);
> +	dev_pm_qos_constraints_init(dev);
>  }
>  
>  /**
> @@ -107,6 +109,7 @@ void device_pm_remove(struct device *dev)
>  {
>  	pr_debug("PM: Removing info for %s:%s\n",
>  		 dev->bus ? dev->bus->name : "No Bus", dev_name(dev));
> +	dev_pm_qos_constraints_destroy(dev);
>  	complete_all(&dev->power.completion);
>  	mutex_lock(&dpm_list_mtx);
>  	list_del_init(&dev->power.entry);
> diff --git a/drivers/base/power/qos.c b/drivers/base/power/qos.c
> new file mode 100644
> index 0000000..465e419
> --- /dev/null
> +++ b/drivers/base/power/qos.c
> @@ -0,0 +1,262 @@
> +/*
> + * This module exposes the interface to kernel space for specifying
> + * per-device PM QoS dependencies. It provides infrastructure for registration
> + * of:
> + *
> + * Dependents on a QoS value : register requests
> + * Watchers of QoS value : get notified when target QoS value changes
> + *
> + * This QoS design is best effort based. Dependents register their QoS needs.
> + * Watchers register to keep track of the current QoS needs of the system.
> + *
> + * Note about the per-device constraint data struct allocation:
> + * . The per-device constraints data struct ptr is tored into the device
> + *    dev_pm_info.
> + * . To minimize the data usage by the per-device constraints, the data struct
> + *   is only allocated at the first call to dev_pm_qos_add_request.
> + * . The data is later free'd when the device is removed from the system.
> + * . The constraints_state variable from dev_pm_info tracks the data struct
> + *    allocation state:
> + *    DEV_PM_QOS_NO_DEVICE: No device present or device removed, no data
> + *     allocated,
> + *    DEV_PM_QOS_DEVICE_PRESENT: Device present, data not allocated and will be
> + *     allocated at the first call to dev_pm_qos_add_request,
> + *    DEV_PM_QOS_ALLOCATED: Device present, data allocated. The per-device
> + *     PM QoS constraints framework is operational and constraints can be
> + *     added, updated or removed using the dev_pm_qos_* API.
> + */
> +
> +/*#define DEBUG*/
> +
> +#include <linux/pm_qos.h>
> +#include <linux/sched.h>
> +#include <linux/spinlock.h>
> +#include <linux/slab.h>
> +#include <linux/time.h>
> +#include <linux/fs.h>
> +#include <linux/device.h>
> +#include <linux/string.h>
> +#include <linux/platform_device.h>
> +#include <linux/init.h>
> +#include <linux/kernel.h>
> +
> +
> +static void dev_pm_qos_constraints_allocate(struct device *dev);
> +
> +int dev_pm_qos_request_active(struct dev_pm_qos_request *req)
> +{
> +	return req->dev != 0;
> +}
> +EXPORT_SYMBOL_GPL(dev_pm_qos_request_active);
> +
> +/**
> + * dev_pm_qos_add_request - inserts new qos request into the list
> + * @req: pointer to a preallocated handle
> + * @dev: target device for the constraint
> + * @value: defines the qos request
> + *
> + * This function inserts a new entry in the device constraints list of
> + * requested qos performance characteristics. It recomputes the aggregate
> + * QoS expectations of parameters and initializes the dev_pm_qos_request
> + * handle.  Caller needs to save this handle for later use in updates and
> + * removal.
> + */
> +void dev_pm_qos_add_request(struct dev_pm_qos_request *req, struct device *dev,
> +			    s32 value)
> +{
> +	if (!req) /*guard against callers passing in null */
> +		return;
> +
> +	if (dev_pm_qos_request_active(req)) {
> +		WARN(1, KERN_ERR "dev_pm_qos_add_request() called for already "
> +			"added request\n");
> +		return;
> +	}
> +	req->dev = dev;
> +
> +	/* Allocate the constraints struct on the first call to add_request */
> +	if (req->dev->power.constraints_state == DEV_PM_QOS_DEVICE_PRESENT)
> +		dev_pm_qos_constraints_allocate(dev);
> +
> +	/* Silently return if the device has been removed */
> +	if (req->dev->power.constraints_state != DEV_PM_QOS_ALLOCATED)
> +		return;
> +
> +	pm_qos_update_target(dev->power.constraints,
> +			     &req->node, PM_QOS_ADD_REQ, value);
> +}
> +EXPORT_SYMBOL_GPL(dev_pm_qos_add_request);
> +
> +/**
> + * dev_pm_qos_update_request - modifies an existing qos request
> + * @req : handle to list element holding a dev_pm_qos request to use
> + * @value: defines the qos request
> + *
> + * Updates an existing dev PM qos request along with updating the
> + * target value.
> + *
> + * Attempts are made to make this code callable on hot code paths.
> + */
> +void dev_pm_qos_update_request(struct dev_pm_qos_request *req,
> +			   s32 new_value)
> +{
> +	if (!req) /*guard against callers passing in null */
> +		return;
> +
> +	if (!dev_pm_qos_request_active(req)) {
> +		WARN(1, KERN_ERR "dev_pm_qos_update_request() called for "
> +			"unknown object\n");
> +		return;
> +	}
> +
> +	/* Silently return if the device has been removed */
> +	if (req->dev->power.constraints_state != DEV_PM_QOS_ALLOCATED)
> +		return;
> +
> +	if (new_value != req->node.prio)
> +		pm_qos_update_target(
> +			req->dev->power.constraints,
> +			&req->node, PM_QOS_UPDATE_REQ, new_value);
> +}
> +EXPORT_SYMBOL_GPL(dev_pm_qos_update_request);
> +
> +/**
> + * dev_pm_qos_remove_request - modifies an existing qos request
> + * @req: handle to request list element
> + *
> + * Will remove pm qos request from the list of constraints and
> + * recompute the current target value. Call this on slow code paths.
> + */
> +void dev_pm_qos_remove_request(struct dev_pm_qos_request *req)
> +{
> +	if (!req) /*guard against callers passing in null */
> +		return;
> +
> +	if (!dev_pm_qos_request_active(req)) {
> +		WARN(1, KERN_ERR "dev_pm_qos_remove_request() called for "
> +			"unknown object\n");
> +		return;
> +	}
> +
> +	/* Silently return if the device has been removed */
> +	if (req->dev->power.constraints_state != DEV_PM_QOS_ALLOCATED)
> +		return;
> +
> +	pm_qos_update_target(req->dev->power.constraints,
> +			     &req->node, PM_QOS_REMOVE_REQ,
> +			     PM_QOS_DEFAULT_VALUE);
> +	memset(req, 0, sizeof(*req));
> +}
> +EXPORT_SYMBOL_GPL(dev_pm_qos_remove_request);
> +
> +/**
> + * dev_pm_qos_add_notifier - sets notification entry for changes to target value
> + * of per-device PM QoS constraints
> + *
> + * @dev: target device for the constraint
> + * @notifier: notifier block managed by caller.
> + *
> + * Will register the notifier into a notification chain that gets called
> + * upon changes to the target value for the device.
> + */
> +int dev_pm_qos_add_notifier(struct device *dev, struct notifier_block *notifier)
> +{
> +	int retval = 0;
> +
> +	/* Silently return if the device has been removed */
> +	if (dev->power.constraints_state != DEV_PM_QOS_ALLOCATED)
> +		return retval;
> +
> +	retval = blocking_notifier_chain_register(
> +			dev->power.constraints->notifiers,
> +			notifier);
> +
> +	return retval;
> +}
> +EXPORT_SYMBOL_GPL(dev_pm_qos_add_notifier);
> +
> +/**
> + * dev_pm_qos_remove_notifier - deletes notification for changes to target value
> + * of per-device PM QoS constraints
> + *
> + * @dev: target device for the constraint
> + * @notifier: notifier block to be removed.
> + *
> + * Will remove the notifier from the notification chain that gets called
> + * upon changes to the target value.
> + */
> +int dev_pm_qos_remove_notifier(struct device *dev,
> +			       struct notifier_block *notifier)
> +{
> +	int retval = 0;
> +
> +	/* Silently return if the device has been removed */
> +	if (dev->power.constraints_state != DEV_PM_QOS_ALLOCATED)
> +		return retval;
> +
> +	retval = blocking_notifier_chain_unregister(
> +			dev->power.constraints->notifiers,
> +			notifier);
> +
> +	return retval;
> +}
> +EXPORT_SYMBOL_GPL(dev_pm_qos_remove_notifier);
> +
> +/* Called at the first call to add_request, for constraint data allocation */
> +static void dev_pm_qos_constraints_allocate(struct device *dev)
> +{
> +	struct pm_qos_constraints *c;
> +	struct blocking_notifier_head *n;
> +
> +	c = kzalloc(sizeof(*c), GFP_KERNEL);
> +	if (!c)
> +		return;
> +
> +	n = kzalloc(sizeof(*n), GFP_KERNEL);
> +	if (!n) {
> +		kfree(c);
> +		return;
> +	}
> +	BLOCKING_INIT_NOTIFIER_HEAD(n);
> +
> +	dev->power.constraints = c;
> +	plist_head_init(&dev->power.constraints->list, &dev->power.lock);
> +	dev->power.constraints->target_value = PM_QOS_DEV_LAT_DEFAULT_VALUE;
> +	dev->power.constraints->default_value =	PM_QOS_DEV_LAT_DEFAULT_VALUE;
> +	dev->power.constraints->type = PM_QOS_MIN;
> +	dev->power.constraints->notifiers = n;
> +	dev->power.constraints_state = DEV_PM_QOS_ALLOCATED;
> +}
> +
> +/* Called from the device PM subsystem at device insertion */
> +void dev_pm_qos_constraints_init(struct device *dev)
> +{
> +	dev->power.constraints_state = DEV_PM_QOS_DEVICE_PRESENT;
> +}
> +
> +/* Called from the device PM subsystem at device removal */
> +void dev_pm_qos_constraints_destroy(struct device *dev)
> +{
> +	struct dev_pm_qos_request *req, *tmp;
> +	enum dev_pm_qos_state constraints_state = dev->power.constraints_state;
> +
> +	dev->power.constraints_state = DEV_PM_QOS_NO_DEVICE;
> +	if (constraints_state == DEV_PM_QOS_ALLOCATED) {
> +		/* Flush the constraints list for the device */
> +		plist_for_each_entry_safe(req, tmp,
> +					  &dev->power.constraints->list,
> +					  node)
> +			/*
> +			 * Update constraints list and call the per-device
> +			 * callbacks if needed
> +			 */
> +			pm_qos_update_target(req->dev->power.constraints,
> +					     &req->node, PM_QOS_REMOVE_REQ,
> +					     PM_QOS_DEFAULT_VALUE);
> +
> +		kfree(dev->power.constraints->notifiers);
> +		kfree(dev->power.constraints);
> +		dev->power.constraints = NULL;
> +	}
> +}
> +
> diff --git a/include/linux/pm.h b/include/linux/pm.h
> index 411e4f4..aa6dc53 100644
> --- a/include/linux/pm.h
> +++ b/include/linux/pm.h
> @@ -421,6 +421,13 @@ enum rpm_request {
>  
>  struct wakeup_source;
>  
> +/* Per-device PM QoS constraints data struct state */
> +enum dev_pm_qos_state {
> +	DEV_PM_QOS_NO_DEVICE,		/* No device present */
> +	DEV_PM_QOS_DEVICE_PRESENT,	/* Device present, data not allocated */
> +	DEV_PM_QOS_ALLOCATED,		/* Device present, data allocated */
> +};
> +
>  struct dev_pm_info {
>  	pm_message_t		power_state;
>  	unsigned int		can_wakeup:1;
> @@ -463,6 +470,8 @@ struct dev_pm_info {
>  	unsigned long		accounting_timestamp;
>  	void			*subsys_data;  /* Owned by the subsystem. */
>  #endif
> +	struct pm_qos_constraints *constraints;
> +	enum dev_pm_qos_state	constraints_state;
>  };
>  
>  extern void update_pm_runtime_accounting(struct device *dev);
> diff --git a/include/linux/pm_qos.h b/include/linux/pm_qos.h
> index 84aa150..178eaa1 100644
> --- a/include/linux/pm_qos.h
> +++ b/include/linux/pm_qos.h
> @@ -19,12 +19,18 @@
>  #define PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE	(2000 * USEC_PER_SEC)
>  #define PM_QOS_NETWORK_LAT_DEFAULT_VALUE	(2000 * USEC_PER_SEC)
>  #define PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE	0
> +#define PM_QOS_DEV_LAT_DEFAULT_VALUE		0
>  
>  struct pm_qos_request {
>  	struct plist_node node;
>  	int pm_qos_class;
>  };
>  
> +struct dev_pm_qos_request {
> +	struct plist_node node;
> +	struct device *dev;
> +};
> +
>  enum pm_qos_type {
>  	PM_QOS_UNITIALIZED,
>  	PM_QOS_MAX,		/* return the largest value */
> @@ -64,6 +70,18 @@ int pm_qos_request(int pm_qos_class);
>  int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier);
>  int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier);
>  int pm_qos_request_active(struct pm_qos_request *req);
> +
> +int dev_pm_qos_request_active(struct dev_pm_qos_request *req);
> +void dev_pm_qos_add_request(struct dev_pm_qos_request *req, struct device *dev,
> +			    s32 value);
> +void dev_pm_qos_update_request(struct dev_pm_qos_request *req, s32 new_value);
> +void dev_pm_qos_remove_request(struct dev_pm_qos_request *req);
> +int dev_pm_qos_add_notifier(struct device *dev,
> +			    struct notifier_block *notifier);
> +int dev_pm_qos_remove_notifier(struct device *dev,
> +			       struct notifier_block *notifier);
> +void dev_pm_qos_constraints_init(struct device *dev);
> +void dev_pm_qos_constraints_destroy(struct device *dev);
>  #else
>  static inline int pm_qos_update_target(struct pm_qos_constraints *c,
>  				       struct plist_node *node,
> @@ -89,6 +107,27 @@ static inline int pm_qos_remove_notifier(int pm_qos_class,
>  			{ return 0; }
>  static inline int pm_qos_request_active(struct pm_qos_request *req)
>  			{ return 0; }
> +
> +static inline int dev_pm_qos_request_active(struct dev_pm_qos_request *req)
> +			{ return 0; }
> +static inline void dev_pm_qos_add_request(struct dev_pm_qos_request *req,
> +					  struct device *dev, s32 value)
> +			{ return; }
> +static inline void dev_pm_qos_update_request(struct dev_pm_qos_request *req,
> +					     s32 new_value)
> +			{ return; }
> +static inline void dev_pm_qos_remove_request(struct dev_pm_qos_request *req)
> +			{ return; }
> +static inline int dev_pm_qos_add_notifier(struct device *dev,
> +					  struct notifier_block *notifier)
> +			{ return 0; }
> +static inline int dev_pm_qos_remove_notifier(struct device *dev,
> +					     struct notifier_block *notifier)
> +			{ return 0; }
> +static inline void dev_pm_qos_constraints_init(struct device *dev)
> +			{ return; }
> +static inline void dev_pm_qos_constraints_destroy(struct device *dev)
> +			{ return; }
>  #endif
>  
>  #endif
> -- 
> 1.7.2.5
>
looks good (except for the use of those enums I don't care for)

--mark