[PATCH 6/7] PM QoS: implement the per-device PM QoS constraints

jean.pihet
2011-08-17T19:40:38Z

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.
A global mutex protects the constraints users from the data being
allocated and free'd.

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 | 339 +++++++++++++++++++++++++++++++++++++++++++
include/linux/pm.h | 9 +
include/linux/pm_qos.h | 42 ++++++
5 files changed, 395 insertions(+), 2 deletions(-)
create mode 100644 drivers/base/power/qos.c

diff --git a/drivers/base/power/Makefile b/drivers/base/power/Makefile
index 2639ae7..b707447 100644
--- a/drivers/base/power/Makefile
+++ b/drivers/base/power/Makefile
@@ -1,4 +1,4 @@
-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-$(CONFIG_PM_TRACE_RTC) += trace.o
@@ -6,4 +6,4 @@ obj-$(CONFIG_PM_OPP) += opp.o
obj-$(CONFIG_PM_GENERIC_DOMAINS) += domain.o
obj-$(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 a854591..956443f 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..9c0a00d
--- /dev/null
+++ b/drivers/base/power/qos.c
@@ -0,0 +1,339 @@
+/*
+ * Devices PM QoS constraints management
+ *
+ * Copyright (C) 2011 Texas Instruments, Inc.
+ *
+ * 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 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.
+ * . A global mutex protects the constraints users from the data being
+ * allocated and free'd.
+ */
+
+#include <linux/pm_qos.h>
+#include <linux/spinlock.h>
+#include <linux/slab.h>
+#include <linux/device.h>
+#include <linux/mutex.h>
+
+
+static DEFINE_MUTEX(dev_pm_qos_mtx);
+
+/*
+ * dev_pm_qos_constraints_allocate
+ * @dev: device to allocate data for
+ *
+ * Called at the first call to add_request, for constraint data allocation
+ * Must be called with the dev_pm_qos_mtx mutex held
+ */
+static int 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 -ENOMEM;
+
+ n = kzalloc(sizeof(*n), GFP_KERNEL);
+ if (!n) {
+ kfree(c);
+ return -ENOMEM;
+ }
+ BLOCKING_INIT_NOTIFIER_HEAD(n);
+
+ dev->power.constraints = c;
+ plist_head_init(&dev->power.constraints->list);
+ 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;
+
+ return 0;
+}
+
+/**
+ * dev_pm_qos_constraints_init
+ * @dev: target device
+ *
+ * Called from the device PM subsystem at device insertion
+ */
+void dev_pm_qos_constraints_init(struct device *dev)
+{
+ mutex_lock(&dev_pm_qos_mtx);
+ dev->power.constraints_state = DEV_PM_QOS_DEVICE_PRESENT;
+ mutex_unlock(&dev_pm_qos_mtx);
+}
+
+/**
+ * dev_pm_qos_constraints_destroy
+ * @dev: target device
+ *
+ * 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;
+
+ mutex_lock(&dev_pm_qos_mtx);
+
+ if (dev->power.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);
+ memset(req, 0, sizeof(*req));
+ }
+
+ kfree(dev->power.constraints->notifiers);
+ kfree(dev->power.constraints);
+ dev->power.constraints = NULL;
+ }
+ dev->power.constraints_state = DEV_PM_QOS_NO_DEVICE;
+
+ mutex_unlock(&dev_pm_qos_mtx);
+}
+
+/**
+ * dev_pm_qos_add_request - inserts new qos request into the list
+ * @dev: target device for the constraint
+ * @req: pointer to a preallocated handle
+ * @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.
+ *
+ * Returns 1 if the aggregated constraint value has changed,
+ * 0 if the aggregated constraint value has not changed,
+ * -EINVAL in case of wrong parameters, -ENODEV if the device has been
+ * removed from the system
+ */
+int dev_pm_qos_add_request(struct device *dev, struct dev_pm_qos_request *req,
+ s32 value)
+{
+ int ret = 0;
+
+ if (!dev || !req) /*guard against callers passing in null */
+ return -EINVAL;
+
+ if (dev_pm_qos_request_active(req)) {
+ WARN(1, KERN_ERR "dev_pm_qos_add_request() called for already "
+ "added request\n");
+ return -EINVAL;
+ }
+
+ mutex_lock(&dev_pm_qos_mtx);
+ req->dev = dev;
+
+ /* Return if the device has been removed */
+ if (req->dev->power.constraints_state == DEV_PM_QOS_NO_DEVICE) {
+ ret = -ENODEV;
+ goto out;
+ }
+
+ /*
+ * Allocate the constraints data on the first call to add_request,
+ * i.e. only if the data is not already allocated and if the device has
+ * not been removed
+ */
+ if (dev->power.constraints_state == DEV_PM_QOS_DEVICE_PRESENT)
+ ret = dev_pm_qos_constraints_allocate(dev);
+
+ if (!ret)
+ ret = pm_qos_update_target(dev->power.constraints, &req->node,
+ PM_QOS_ADD_REQ, value);
+
+out:
+ mutex_unlock(&dev_pm_qos_mtx);
+ return ret;
+}
+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
+ * @new_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.
+ *
+ * Returns 1 if the aggregated constraint value has changed,
+ * 0 if the aggregated constraint value has not changed,
+ * -EINVAL in case of wrong parameters, -ENODEV if the device has been
+ * removed from the system
+ */
+int dev_pm_qos_update_request(struct dev_pm_qos_request *req,
+ s32 new_value)
+{
+ int ret = 0;
+
+ if (!req) /*guard against callers passing in null */
+ return -EINVAL;
+
+ if (!dev_pm_qos_request_active(req)) {
+ WARN(1, KERN_ERR "dev_pm_qos_update_request() called for "
+ "unknown object\n");
+ return -EINVAL;
+ }
+
+ mutex_lock(&dev_pm_qos_mtx);
+
+ if (req->dev->power.constraints_state == DEV_PM_QOS_ALLOCATED) {
+ if (new_value != req->node.prio)
+ ret = pm_qos_update_target(req->dev->power.constraints,
+ &req->node,
+ PM_QOS_UPDATE_REQ,
+ new_value);
+ } else {
+ /* Return if the device has been removed */
+ ret = -ENODEV;
+ }
+
+ mutex_unlock(&dev_pm_qos_mtx);
+ return ret;
+}
+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.
+ *
+ * Returns 1 if the aggregated constraint value has changed,
+ * 0 if the aggregated constraint value has not changed,
+ * -EINVAL in case of wrong parameters, -ENODEV if the device has been
+ * removed from the system
+ */
+int dev_pm_qos_remove_request(struct dev_pm_qos_request *req)
+{
+ int ret = 0;
+
+ if (!req) /*guard against callers passing in null */
+ return -EINVAL;
+
+ if (!dev_pm_qos_request_active(req)) {
+ WARN(1, KERN_ERR "dev_pm_qos_remove_request() called for "
+ "unknown object\n");
+ return -EINVAL;
+ }
+
+ mutex_lock(&dev_pm_qos_mtx);
+
+ if (req->dev->power.constraints_state == DEV_PM_QOS_ALLOCATED) {
+ ret = pm_qos_update_target(req->dev->power.constraints,
+ &req->node, PM_QOS_REMOVE_REQ,
+ PM_QOS_DEFAULT_VALUE);
+ memset(req, 0, sizeof(*req));
+ } else {
+ /* Return if the device has been removed */
+ ret = -ENODEV;
+ }
+
+ mutex_unlock(&dev_pm_qos_mtx);
+ return ret;
+}
+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;
+
+ mutex_lock(&dev_pm_qos_mtx);
+
+ /* Silently return if the device has been removed */
+ if (dev->power.constraints_state != DEV_PM_QOS_ALLOCATED)
+ goto out;
+
+ retval = blocking_notifier_chain_register(
+ dev->power.constraints->notifiers,
+ notifier);
+
+out:
+ mutex_unlock(&dev_pm_qos_mtx);
+ 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;
+
+ mutex_lock(&dev_pm_qos_mtx);
+
+ /* Silently return if the device has been removed */
+ if (dev->power.constraints_state != DEV_PM_QOS_ALLOCATED)
+ goto out;
+
+ retval = blocking_notifier_chain_unregister(
+ dev->power.constraints->notifiers,
+ notifier);
+
+out:
+ mutex_unlock(&dev_pm_qos_mtx);
+ return retval;
+}
+EXPORT_SYMBOL_GPL(dev_pm_qos_remove_notifier);
+
diff --git a/include/linux/pm.h b/include/linux/pm.h
index f7c84c9..7a48951 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;
#endif
void *subsys_data; /* Owned by the subsystem. */
+ 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..c35e189 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 */
@@ -51,6 +57,11 @@ enum pm_qos_req_action {
PM_QOS_REMOVE_REQ /* Remove an existing request */
};

+static inline int dev_pm_qos_request_active(struct dev_pm_qos_request *req)
+{
+ return req->dev != 0;
+}
+
#ifdef CONFIG_PM
int pm_qos_update_target(struct pm_qos_constraints *c, struct plist_node *node,
enum pm_qos_req_action action, int value);
@@ -64,6 +75,17 @@ 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_add_request(struct device *dev, struct dev_pm_qos_request *req,
+ s32 value);
+int dev_pm_qos_update_request(struct dev_pm_qos_request *req, s32 new_value);
+int 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 +111,26 @@ 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_add_request(struct device *dev,
+ struct dev_pm_qos_request *req,
+ s32 value)
+ { return; }
+static inline int dev_pm_qos_update_request(struct dev_pm_qos_request *req,
+ s32 new_value)
+ { return; }
+static inline int 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
--
1.7.4.1