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PM: QoS: Introduce frequency QoS
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Introduce frequency QoS, based on the "raw" low-level PM QoS, to
represent min and max frequency requests and aggregate constraints.

The min and max frequency requests are to be represented by
struct freq_qos_request objects and the aggregate constraints are to
be represented by struct freq_constraints objects.  The latter are
expected to be initialized with the help of freq_constraints_init().

The freq_qos_read_value() helper is defined to retrieve the aggregate
constraints values from a given struct freq_constraints object and
there are the freq_qos_add_request(), freq_qos_update_request() and
freq_qos_remove_request() helpers to manipulate the min and max
frequency requests.  It is assumed that the the helpers will not
run concurrently with each other for the same struct freq_qos_request
object, so if that may be the case, their uses must ensure proper
synchronization between them (e.g. through locking).

In addition, freq_qos_add_notifier() and freq_qos_remove_notifier()
are provided to add and remove notifiers that will trigger on aggregate
constraint changes to and from a given struct freq_constraints object,
respectively.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
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Rafael J. Wysocki committed Oct 21, 2019
1 parent 7d194c2 commit 77751a4
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44 changes: 44 additions & 0 deletions include/linux/pm_qos.h
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Original file line number Diff line number Diff line change
Expand Up @@ -267,4 +267,48 @@ static inline s32 dev_pm_qos_raw_resume_latency(struct device *dev)
}
#endif

#define FREQ_QOS_MIN_DEFAULT_VALUE 0
#define FREQ_QOS_MAX_DEFAULT_VALUE (-1)

enum freq_qos_req_type {
FREQ_QOS_MIN = 1,
FREQ_QOS_MAX,
};

struct freq_constraints {
struct pm_qos_constraints min_freq;
struct blocking_notifier_head min_freq_notifiers;
struct pm_qos_constraints max_freq;
struct blocking_notifier_head max_freq_notifiers;
};

struct freq_qos_request {
enum freq_qos_req_type type;
struct plist_node pnode;
struct freq_constraints *qos;
};

static inline int freq_qos_request_active(struct freq_qos_request *req)
{
return !IS_ERR_OR_NULL(req->qos);
}

void freq_constraints_init(struct freq_constraints *qos);

s32 freq_qos_read_value(struct freq_constraints *qos,
enum freq_qos_req_type type);

int freq_qos_add_request(struct freq_constraints *qos,
struct freq_qos_request *req,
enum freq_qos_req_type type, s32 value);
int freq_qos_update_request(struct freq_qos_request *req, s32 new_value);
int freq_qos_remove_request(struct freq_qos_request *req);

int freq_qos_add_notifier(struct freq_constraints *qos,
enum freq_qos_req_type type,
struct notifier_block *notifier);
int freq_qos_remove_notifier(struct freq_constraints *qos,
enum freq_qos_req_type type,
struct notifier_block *notifier);

#endif
240 changes: 240 additions & 0 deletions kernel/power/qos.c
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Original file line number Diff line number Diff line change
Expand Up @@ -650,3 +650,243 @@ static int __init pm_qos_power_init(void)
}

late_initcall(pm_qos_power_init);

/* Definitions related to the frequency QoS below. */

/**
* freq_constraints_init - Initialize frequency QoS constraints.
* @qos: Frequency QoS constraints to initialize.
*/
void freq_constraints_init(struct freq_constraints *qos)
{
struct pm_qos_constraints *c;

c = &qos->min_freq;
plist_head_init(&c->list);
c->target_value = FREQ_QOS_MIN_DEFAULT_VALUE;
c->default_value = FREQ_QOS_MIN_DEFAULT_VALUE;
c->no_constraint_value = FREQ_QOS_MIN_DEFAULT_VALUE;
c->type = PM_QOS_MAX;
c->notifiers = &qos->min_freq_notifiers;
BLOCKING_INIT_NOTIFIER_HEAD(c->notifiers);

c = &qos->max_freq;
plist_head_init(&c->list);
c->target_value = FREQ_QOS_MAX_DEFAULT_VALUE;
c->default_value = FREQ_QOS_MAX_DEFAULT_VALUE;
c->no_constraint_value = FREQ_QOS_MAX_DEFAULT_VALUE;
c->type = PM_QOS_MIN;
c->notifiers = &qos->max_freq_notifiers;
BLOCKING_INIT_NOTIFIER_HEAD(c->notifiers);
}

/**
* freq_qos_read_value - Get frequency QoS constraint for a given list.
* @qos: Constraints to evaluate.
* @type: QoS request type.
*/
s32 freq_qos_read_value(struct freq_constraints *qos,
enum freq_qos_req_type type)
{
s32 ret;

switch (type) {
case FREQ_QOS_MIN:
ret = IS_ERR_OR_NULL(qos) ?
FREQ_QOS_MIN_DEFAULT_VALUE :
pm_qos_read_value(&qos->min_freq);
break;
case FREQ_QOS_MAX:
ret = IS_ERR_OR_NULL(qos) ?
FREQ_QOS_MAX_DEFAULT_VALUE :
pm_qos_read_value(&qos->max_freq);
break;
default:
WARN_ON(1);
ret = 0;
}

return ret;
}

/**
* freq_qos_apply - Add/modify/remove frequency QoS request.
* @req: Constraint request to apply.
* @action: Action to perform (add/update/remove).
* @value: Value to assign to the QoS request.
*/
static int freq_qos_apply(struct freq_qos_request *req,
enum pm_qos_req_action action, s32 value)
{
int ret;

switch(req->type) {
case FREQ_QOS_MIN:
ret = pm_qos_update_target(&req->qos->min_freq, &req->pnode,
action, value);
break;
case FREQ_QOS_MAX:
ret = pm_qos_update_target(&req->qos->max_freq, &req->pnode,
action, value);
break;
default:
ret = -EINVAL;
}

return ret;
}

/**
* freq_qos_add_request - Insert new frequency QoS request into a given list.
* @qos: Constraints to update.
* @req: Preallocated request object.
* @type: Request type.
* @value: Request value.
*
* Insert a new entry into the @qos list of requests, recompute the effective
* QoS constraint value for that list and initialize the @req object. The
* caller needs to save that object for later use in updates and removal.
*
* Return 1 if the effective constraint value has changed, 0 if the effective
* constraint value has not changed, or a negative error code on failures.
*/
int freq_qos_add_request(struct freq_constraints *qos,
struct freq_qos_request *req,
enum freq_qos_req_type type, s32 value)
{
int ret;

if (IS_ERR_OR_NULL(qos) || !req)
return -EINVAL;

if (WARN(freq_qos_request_active(req),
"%s() called for active request\n", __func__))
return -EINVAL;

req->qos = qos;
req->type = type;
ret = freq_qos_apply(req, PM_QOS_ADD_REQ, value);
if (ret < 0) {
req->qos = NULL;
req->type = 0;
}

return ret;
}
EXPORT_SYMBOL_GPL(freq_qos_add_request);

/**
* freq_qos_update_request - Modify existing frequency QoS request.
* @req: Request to modify.
* @new_value: New request value.
*
* Update an existing frequency QoS request along with the effective constraint
* value for the list of requests it belongs to.
*
* Return 1 if the effective constraint value has changed, 0 if the effective
* constraint value has not changed, or a negative error code on failures.
*/
int freq_qos_update_request(struct freq_qos_request *req, s32 new_value)
{
if (!req)
return -EINVAL;

if (WARN(!freq_qos_request_active(req),
"%s() called for unknown object\n", __func__))
return -EINVAL;

if (req->pnode.prio == new_value)
return 0;

return freq_qos_apply(req, PM_QOS_UPDATE_REQ, new_value);
}
EXPORT_SYMBOL_GPL(freq_qos_update_request);

/**
* freq_qos_remove_request - Remove frequency QoS request from its list.
* @req: Request to remove.
*
* Remove the given frequency QoS request from the list of constraints it
* belongs to and recompute the effective constraint value for that list.
*
* Return 1 if the effective constraint value has changed, 0 if the effective
* constraint value has not changed, or a negative error code on failures.
*/
int freq_qos_remove_request(struct freq_qos_request *req)
{
if (!req)
return -EINVAL;

if (WARN(!freq_qos_request_active(req),
"%s() called for unknown object\n", __func__))
return -EINVAL;

return freq_qos_apply(req, PM_QOS_REMOVE_REQ, PM_QOS_DEFAULT_VALUE);
}
EXPORT_SYMBOL_GPL(freq_qos_remove_request);

/**
* freq_qos_add_notifier - Add frequency QoS change notifier.
* @qos: List of requests to add the notifier to.
* @type: Request type.
* @notifier: Notifier block to add.
*/
int freq_qos_add_notifier(struct freq_constraints *qos,
enum freq_qos_req_type type,
struct notifier_block *notifier)
{
int ret;

if (IS_ERR_OR_NULL(qos) || !notifier)
return -EINVAL;

switch (type) {
case FREQ_QOS_MIN:
ret = blocking_notifier_chain_register(qos->min_freq.notifiers,
notifier);
break;
case FREQ_QOS_MAX:
ret = blocking_notifier_chain_register(qos->max_freq.notifiers,
notifier);
break;
default:
WARN_ON(1);
ret = -EINVAL;
}

return ret;
}
EXPORT_SYMBOL_GPL(freq_qos_add_notifier);

/**
* freq_qos_remove_notifier - Remove frequency QoS change notifier.
* @qos: List of requests to remove the notifier from.
* @type: Request type.
* @notifier: Notifier block to remove.
*/
int freq_qos_remove_notifier(struct freq_constraints *qos,
enum freq_qos_req_type type,
struct notifier_block *notifier)
{
int ret;

if (IS_ERR_OR_NULL(qos) || !notifier)
return -EINVAL;

switch (type) {
case FREQ_QOS_MIN:
ret = blocking_notifier_chain_unregister(qos->min_freq.notifiers,
notifier);
break;
case FREQ_QOS_MAX:
ret = blocking_notifier_chain_unregister(qos->max_freq.notifiers,
notifier);
break;
default:
WARN_ON(1);
ret = -EINVAL;
}

return ret;
}
EXPORT_SYMBOL_GPL(freq_qos_remove_notifier);

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