Not all drivers support this attribute. If it isn't supported,
attempts to read or write it will yield I/O errors.
-What: /sys/devices/.../power/pm_qos_latency_us
+What: /sys/devices/.../power/pm_qos_resume_latency_us
Date: March 2012
Contact: Rafael J. Wysocki <rjw@rjwysocki.net>
Description:
This attribute has no effect on system-wide suspend/resume and
hibernation.
+What: /sys/devices/.../power/pm_qos_latency_tolerance_us
+Date: January 2014
+Contact: Rafael J. Wysocki <rjw@rjwysocki.net>
+Description:
+ The /sys/devices/.../power/pm_qos_latency_tolerance_us attribute
+ contains the PM QoS active state latency tolerance limit for the
+ given device in microseconds. That is the maximum memory access
+ latency the device can suffer without any visible adverse
+ effects on user space functionality. If that value is the
+ string "any", the latency does not matter to user space at all,
+ but hardware should not be allowed to set the latency tolerance
+ for the device automatically.
+
+ Reading "auto" from this file means that the maximum memory
+ access latency for the device may be determined automatically
+ by the hardware as needed. Writing "auto" to it allows the
+ hardware to be switched to this mode if there are no other
+ latency tolerance requirements from the kernel side.
+
+ This attribute is only present if the feature controlled by it
+ is supported by the hardware.
+
+ This attribute has no effect on runtime suspend and resume of
+ devices and on system-wide suspend/resume and hibernation.
+
What: /sys/devices/.../power/pm_qos_no_power_off
Date: September 2012
Contact: Rafael J. Wysocki <rjw@rjwysocki.net>
2. PM QoS per-device latency and flags framework
-For each device, there are two lists of PM QoS requests. One is maintained
-along with the aggregated target of resume latency value and the other is for
-PM QoS flags. Values are updated in response to changes of the request list.
+For each device, there are three lists of PM QoS requests. Two of them are
+maintained along with the aggregated targets of resume latency and active
+state latency tolerance (in microseconds) and the third one is for PM QoS flags.
+Values are updated in response to changes of the request list.
-Target resume latency value is simply the minimum of the request values held in
-the parameter list elements. The PM QoS flags aggregate value is a gather
-(bitwise OR) of all list elements' values. Two device PM QoS flags are defined
-currently: PM_QOS_FLAG_NO_POWER_OFF and PM_QOS_FLAG_REMOTE_WAKEUP.
+The target values of resume latency and active state latency tolerance are
+simply the minimum of the request values held in the parameter list elements.
+The PM QoS flags aggregate value is a gather (bitwise OR) of all list elements'
+values. Two device PM QoS flags are defined currently: PM_QOS_FLAG_NO_POWER_OFF
+and PM_QOS_FLAG_REMOTE_WAKEUP.
-Note: the aggregated target value is implemented in such a way that reading the
-aggregated value does not require any locking mechanism.
+Note: The aggregated target values are implemented in such a way that reading
+the aggregated value does not require any locking mechanism.
From kernel mode the use of this interface is the following:
int dev_pm_qos_remove_global_notifier(notifier):
Removes the notification callback function from the global notification tree
of the framework.
+
+
+Active state latency tolerance
+
+This device PM QoS type is used to support systems in which hardware may switch
+to energy-saving operation modes on the fly. In those systems, if the operation
+mode chosen by the hardware attempts to save energy in an overly aggressive way,
+it may cause excess latencies to be visible to software, causing it to miss
+certain protocol requirements or target frame or sample rates etc.
+
+If there is a latency tolerance control mechanism for a given device available
+to software, the .set_latency_tolerance callback in that device's dev_pm_info
+structure should be populated. The routine pointed to by it is should implement
+whatever is necessary to transfer the effective requirement value to the
+hardware.
+
+Whenever the effective latency tolerance changes for the device, its
+.set_latency_tolerance() callback will be executed and the effective value will
+be passed to it. If that value is negative, which means that the list of
+latency tolerance requirements for the device is empty, the callback is expected
+to switch the underlying hardware latency tolerance control mechanism to an
+autonomous mode if available. If that value is PM_QOS_LATENCY_ANY, in turn, and
+the hardware supports a special "no requirement" setting, the callback is
+expected to use it. That allows software to prevent the hardware from
+automatically updating the device's latency tolerance in response to its power
+state changes (e.g. during transitions from D3cold to D0), which generally may
+be done in the autonomous latency tolerance control mode.
+
+If .set_latency_tolerance() is present for the device, sysfs attribute
+pm_qos_latency_tolerance_us will be present in the devivce's power directory.
+Then, user space can use that attribute to specify its latency tolerance
+requirement for the device, if any. Writing "any" to it means "no requirement,
+but do not let the hardware control latency tolerance" and writing "auto" to it
+allows the hardware to be switched to the autonomous mode if there are no other
+requirements from the kernel side in the device's list.
+
+Kernel code can use the functions described above along with the
+DEV_PM_QOS_LATENCY_TOLERANCE device PM QoS type to add, remove and update
+latency tolerance requirements for devices.
req);
}
break;
+ case DEV_PM_QOS_LATENCY_TOLERANCE:
+ ret = pm_qos_update_target(&qos->latency_tolerance,
+ &req->data.pnode, action, value);
+ if (ret) {
+ value = pm_qos_read_value(&qos->latency_tolerance);
+ req->dev->power.set_latency_tolerance(req->dev, value);
+ }
+ break;
case DEV_PM_QOS_FLAGS:
ret = pm_qos_update_flags(&qos->flags, &req->data.flr,
action, value);
c->type = PM_QOS_MIN;
c->notifiers = n;
+ c = &qos->latency_tolerance;
+ plist_head_init(&c->list);
+ c->target_value = PM_QOS_LATENCY_TOLERANCE_DEFAULT_VALUE;
+ c->default_value = PM_QOS_LATENCY_TOLERANCE_DEFAULT_VALUE;
+ c->no_constraint_value = PM_QOS_LATENCY_TOLERANCE_NO_CONSTRAINT;
+ c->type = PM_QOS_MIN;
+
INIT_LIST_HEAD(&qos->flags.list);
spin_lock_irq(&dev->power.lock);
apply_constraint(req, PM_QOS_REMOVE_REQ, PM_QOS_DEFAULT_VALUE);
memset(req, 0, sizeof(*req));
}
+ c = &qos->latency_tolerance;
+ plist_for_each_entry_safe(req, tmp, &c->list, data.pnode) {
+ apply_constraint(req, PM_QOS_REMOVE_REQ, PM_QOS_DEFAULT_VALUE);
+ memset(req, 0, sizeof(*req));
+ }
f = &qos->flags;
list_for_each_entry_safe(req, tmp, &f->list, data.flr.node) {
apply_constraint(req, PM_QOS_REMOVE_REQ, PM_QOS_DEFAULT_VALUE);
mutex_unlock(&dev_pm_qos_sysfs_mtx);
}
+static bool dev_pm_qos_invalid_request(struct device *dev,
+ struct dev_pm_qos_request *req)
+{
+ return !req || (req->type == DEV_PM_QOS_LATENCY_TOLERANCE
+ && !dev->power.set_latency_tolerance);
+}
+
+static int __dev_pm_qos_add_request(struct device *dev,
+ struct dev_pm_qos_request *req,
+ enum dev_pm_qos_req_type type, s32 value)
+{
+ int ret = 0;
+
+ if (!dev || dev_pm_qos_invalid_request(dev, req))
+ return -EINVAL;
+
+ if (WARN(dev_pm_qos_request_active(req),
+ "%s() called for already added request\n", __func__))
+ return -EINVAL;
+
+ if (IS_ERR(dev->power.qos))
+ ret = -ENODEV;
+ else if (!dev->power.qos)
+ ret = dev_pm_qos_constraints_allocate(dev);
+
+ trace_dev_pm_qos_add_request(dev_name(dev), type, value);
+ if (!ret) {
+ req->dev = dev;
+ req->type = type;
+ ret = apply_constraint(req, PM_QOS_ADD_REQ, value);
+ }
+ return ret;
+}
+
/**
* dev_pm_qos_add_request - inserts new qos request into the list
* @dev: target device for the constraint
int dev_pm_qos_add_request(struct device *dev, struct dev_pm_qos_request *req,
enum dev_pm_qos_req_type type, s32 value)
{
- int ret = 0;
-
- if (!dev || !req) /*guard against callers passing in null */
- return -EINVAL;
-
- if (WARN(dev_pm_qos_request_active(req),
- "%s() called for already added request\n", __func__))
- return -EINVAL;
+ int ret;
mutex_lock(&dev_pm_qos_mtx);
-
- if (IS_ERR(dev->power.qos))
- ret = -ENODEV;
- else if (!dev->power.qos)
- ret = dev_pm_qos_constraints_allocate(dev);
-
- trace_dev_pm_qos_add_request(dev_name(dev), type, value);
- if (!ret) {
- req->dev = dev;
- req->type = type;
- ret = apply_constraint(req, PM_QOS_ADD_REQ, value);
- }
-
+ ret = __dev_pm_qos_add_request(dev, req, type, value);
mutex_unlock(&dev_pm_qos_mtx);
-
return ret;
}
EXPORT_SYMBOL_GPL(dev_pm_qos_add_request);
switch(req->type) {
case DEV_PM_QOS_RESUME_LATENCY:
+ case DEV_PM_QOS_LATENCY_TOLERANCE:
curr_value = req->data.pnode.prio;
break;
case DEV_PM_QOS_FLAGS:
req = dev->power.qos->resume_latency_req;
dev->power.qos->resume_latency_req = NULL;
break;
+ case DEV_PM_QOS_LATENCY_TOLERANCE:
+ req = dev->power.qos->latency_tolerance_req;
+ dev->power.qos->latency_tolerance_req = NULL;
+ break;
case DEV_PM_QOS_FLAGS:
req = dev->power.qos->flags_req;
dev->power.qos->flags_req = NULL;
pm_runtime_put(dev);
return ret;
}
+
+/**
+ * dev_pm_qos_get_user_latency_tolerance - Get user space latency tolerance.
+ * @dev: Device to obtain the user space latency tolerance for.
+ */
+s32 dev_pm_qos_get_user_latency_tolerance(struct device *dev)
+{
+ s32 ret;
+
+ mutex_lock(&dev_pm_qos_mtx);
+ ret = IS_ERR_OR_NULL(dev->power.qos)
+ || !dev->power.qos->latency_tolerance_req ?
+ PM_QOS_LATENCY_TOLERANCE_NO_CONSTRAINT :
+ dev->power.qos->latency_tolerance_req->data.pnode.prio;
+ mutex_unlock(&dev_pm_qos_mtx);
+ return ret;
+}
+
+/**
+ * dev_pm_qos_update_user_latency_tolerance - Update user space latency tolerance.
+ * @dev: Device to update the user space latency tolerance for.
+ * @val: New user space latency tolerance for @dev (negative values disable).
+ */
+int dev_pm_qos_update_user_latency_tolerance(struct device *dev, s32 val)
+{
+ int ret;
+
+ mutex_lock(&dev_pm_qos_mtx);
+
+ if (IS_ERR_OR_NULL(dev->power.qos)
+ || !dev->power.qos->latency_tolerance_req) {
+ struct dev_pm_qos_request *req;
+
+ if (val < 0) {
+ ret = -EINVAL;
+ goto out;
+ }
+ req = kzalloc(sizeof(*req), GFP_KERNEL);
+ if (!req) {
+ ret = -ENOMEM;
+ goto out;
+ }
+ ret = __dev_pm_qos_add_request(dev, req, DEV_PM_QOS_LATENCY_TOLERANCE, val);
+ if (ret < 0) {
+ kfree(req);
+ goto out;
+ }
+ dev->power.qos->latency_tolerance_req = req;
+ } else {
+ if (val < 0) {
+ __dev_pm_qos_drop_user_request(dev, DEV_PM_QOS_LATENCY_TOLERANCE);
+ ret = 0;
+ } else {
+ ret = __dev_pm_qos_update_request(dev->power.qos->latency_tolerance_req, val);
+ }
+ }
+
+ out:
+ mutex_unlock(&dev_pm_qos_mtx);
+ return ret;
+}
#else /* !CONFIG_PM_RUNTIME */
static void __dev_pm_qos_hide_latency_limit(struct device *dev) {}
static void __dev_pm_qos_hide_flags(struct device *dev) {}
static DEVICE_ATTR(pm_qos_resume_latency_us, 0644,
pm_qos_resume_latency_show, pm_qos_resume_latency_store);
+static ssize_t pm_qos_latency_tolerance_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ s32 value = dev_pm_qos_get_user_latency_tolerance(dev);
+
+ if (value < 0)
+ return sprintf(buf, "auto\n");
+ else if (value == PM_QOS_LATENCY_ANY)
+ return sprintf(buf, "any\n");
+
+ return sprintf(buf, "%d\n", value);
+}
+
+static ssize_t pm_qos_latency_tolerance_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t n)
+{
+ s32 value;
+ int ret;
+
+ if (kstrtos32(buf, 0, &value)) {
+ if (!strcmp(buf, "auto") || !strcmp(buf, "auto\n"))
+ value = PM_QOS_LATENCY_TOLERANCE_NO_CONSTRAINT;
+ else if (!strcmp(buf, "any") || !strcmp(buf, "any\n"))
+ value = PM_QOS_LATENCY_ANY;
+ }
+ ret = dev_pm_qos_update_user_latency_tolerance(dev, value);
+ return ret < 0 ? ret : n;
+}
+
+static DEVICE_ATTR(pm_qos_latency_tolerance_us, 0644,
+ pm_qos_latency_tolerance_show, pm_qos_latency_tolerance_store);
+
static ssize_t pm_qos_no_power_off_show(struct device *dev,
struct device_attribute *attr,
char *buf)
.attrs = pm_qos_resume_latency_attrs,
};
+static struct attribute *pm_qos_latency_tolerance_attrs[] = {
+#ifdef CONFIG_PM_RUNTIME
+ &dev_attr_pm_qos_latency_tolerance_us.attr,
+#endif /* CONFIG_PM_RUNTIME */
+ NULL,
+};
+static struct attribute_group pm_qos_latency_tolerance_attr_group = {
+ .name = power_group_name,
+ .attrs = pm_qos_latency_tolerance_attrs,
+};
+
static struct attribute *pm_qos_flags_attrs[] = {
#ifdef CONFIG_PM_RUNTIME
&dev_attr_pm_qos_no_power_off.attr,
if (rc)
goto err_out;
}
-
if (device_can_wakeup(dev)) {
rc = sysfs_merge_group(&dev->kobj, &pm_wakeup_attr_group);
- if (rc) {
- if (pm_runtime_callbacks_present(dev))
- sysfs_unmerge_group(&dev->kobj,
- &pm_runtime_attr_group);
- goto err_out;
- }
+ if (rc)
+ goto err_runtime;
+ }
+ if (dev->power.set_latency_tolerance) {
+ rc = sysfs_merge_group(&dev->kobj,
+ &pm_qos_latency_tolerance_attr_group);
+ if (rc)
+ goto err_wakeup;
}
return 0;
+ err_wakeup:
+ sysfs_unmerge_group(&dev->kobj, &pm_wakeup_attr_group);
+ err_runtime:
+ sysfs_unmerge_group(&dev->kobj, &pm_runtime_attr_group);
err_out:
sysfs_remove_group(&dev->kobj, &pm_attr_group);
return rc;
void dpm_sysfs_remove(struct device *dev)
{
+ sysfs_unmerge_group(&dev->kobj, &pm_qos_latency_tolerance_attr_group);
dev_pm_qos_constraints_destroy(dev);
rpm_sysfs_remove(dev);
sysfs_unmerge_group(&dev->kobj, &pm_wakeup_attr_group);
unsigned long accounting_timestamp;
#endif
struct pm_subsys_data *subsys_data; /* Owned by the subsystem. */
+ void (*set_latency_tolerance)(struct device *, s32);
struct dev_pm_qos *qos;
};
#define PM_QOS_NETWORK_LAT_DEFAULT_VALUE (2000 * USEC_PER_SEC)
#define PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE 0
#define PM_QOS_RESUME_LATENCY_DEFAULT_VALUE 0
+#define PM_QOS_LATENCY_TOLERANCE_DEFAULT_VALUE 0
+#define PM_QOS_LATENCY_TOLERANCE_NO_CONSTRAINT (-1)
+#define PM_QOS_LATENCY_ANY ((s32)(~(__u32)0 >> 1))
#define PM_QOS_FLAG_NO_POWER_OFF (1 << 0)
#define PM_QOS_FLAG_REMOTE_WAKEUP (1 << 1)
enum dev_pm_qos_req_type {
DEV_PM_QOS_RESUME_LATENCY = 1,
+ DEV_PM_QOS_LATENCY_TOLERANCE,
DEV_PM_QOS_FLAGS,
};
struct dev_pm_qos {
struct pm_qos_constraints resume_latency;
+ struct pm_qos_constraints latency_tolerance;
struct pm_qos_flags flags;
struct dev_pm_qos_request *resume_latency_req;
+ struct dev_pm_qos_request *latency_tolerance_req;
struct dev_pm_qos_request *flags_req;
};
int dev_pm_qos_expose_flags(struct device *dev, s32 value);
void dev_pm_qos_hide_flags(struct device *dev);
int dev_pm_qos_update_flags(struct device *dev, s32 mask, bool set);
+s32 dev_pm_qos_get_user_latency_tolerance(struct device *dev);
+int dev_pm_qos_update_user_latency_tolerance(struct device *dev, s32 val);
static inline s32 dev_pm_qos_requested_resume_latency(struct device *dev)
{
static inline void dev_pm_qos_hide_flags(struct device *dev) {}
static inline int dev_pm_qos_update_flags(struct device *dev, s32 m, bool set)
{ return 0; }
+static inline s32 dev_pm_qos_get_user_latency_tolerance(struct device *dev)
+ { return PM_QOS_LATENCY_TOLERANCE_NO_CONSTRAINT; }
+static inline int dev_pm_qos_update_user_latency_tolerance(struct device *dev, s32 val)
+ { return 0; }
static inline s32 dev_pm_qos_requested_resume_latency(struct device *dev) { return 0; }
static inline s32 dev_pm_qos_requested_flags(struct device *dev) { return 0; }
{
unsigned long flags;
int prev_value, curr_value, new_value;
+ int ret;
spin_lock_irqsave(&pm_qos_lock, flags);
prev_value = pm_qos_get_value(c);
trace_pm_qos_update_target(action, prev_value, curr_value);
if (prev_value != curr_value) {
- blocking_notifier_call_chain(c->notifiers,
- (unsigned long)curr_value,
- NULL);
- return 1;
+ ret = 1;
+ if (c->notifiers)
+ blocking_notifier_call_chain(c->notifiers,
+ (unsigned long)curr_value,
+ NULL);
} else {
- return 0;
+ ret = 0;
}
+ return ret;
}
/**
projects / users / hch / xfs.git / commitdiff