cregit-Linux how code gets into the kernel

Release 4.15 kernel/power/qos.c

Directory: kernel/power
 * This module exposes the interface to kernel space for specifying
 * 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.
 * There are 3 basic classes of QoS parameter: latency, timeout, throughput
 * each have defined units:
 * latency: usec
 * timeout: usec <-- currently not used.
 * throughput: kbs (kilo byte / sec)
 * There are lists of pm_qos_objects each one wrapping requests, notifiers
 * User mode requests on a QOS parameter register themselves to the
 * subsystem by opening the device node /dev/... and writing there request to
 * the node.  As long as the process holds a file handle open to the node the
 * client continues to be accounted for.  Upon file release the usermode
 * request is removed and a new qos target is computed.  This way when the
 * request that the application has is cleaned up when closes the file
 * pointer or exits the pm_qos_object will get an opportunity to clean up.
 * Mark Gross <>

/*#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/miscdevice.h>
#include <linux/string.h>
#include <linux/platform_device.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/debugfs.h>
#include <linux/seq_file.h>

#include <linux/uaccess.h>
#include <linux/export.h>
#include <trace/events/power.h>

 * locking rule: all changes to constraints or notifiers lists
 * or pm_qos_object list and pm_qos_objects need to happen with pm_qos_lock
 * held, taken with _irqsave.  One lock to rule them all

struct pm_qos_object {
struct pm_qos_constraints *constraints;
struct miscdevice pm_qos_power_miscdev;
char *name;

static DEFINE_SPINLOCK(pm_qos_lock);

static struct pm_qos_object null_pm_qos;

static BLOCKING_NOTIFIER_HEAD(cpu_dma_lat_notifier);

static struct pm_qos_constraints cpu_dma_constraints = {
	.list = PLIST_HEAD_INIT(cpu_dma_constraints.list),
	.no_constraint_value = PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE,
	.type = PM_QOS_MIN,
	.notifiers = &cpu_dma_lat_notifier,

static struct pm_qos_object cpu_dma_pm_qos = {
	.constraints = &cpu_dma_constraints,
	.name = "cpu_dma_latency",

static BLOCKING_NOTIFIER_HEAD(network_lat_notifier);

static struct pm_qos_constraints network_lat_constraints = {
	.list = PLIST_HEAD_INIT(network_lat_constraints.list),
	.no_constraint_value = PM_QOS_NETWORK_LAT_DEFAULT_VALUE,
	.type = PM_QOS_MIN,
	.notifiers = &network_lat_notifier,

static struct pm_qos_object network_lat_pm_qos = {
	.constraints = &network_lat_constraints,
	.name = "network_latency",

static BLOCKING_NOTIFIER_HEAD(network_throughput_notifier);

static struct pm_qos_constraints network_tput_constraints = {
	.list = PLIST_HEAD_INIT(network_tput_constraints.list),
	.type = PM_QOS_MAX,
	.notifiers = &network_throughput_notifier,

static struct pm_qos_object network_throughput_pm_qos = {
	.constraints = &network_tput_constraints,
	.name = "network_throughput",

static BLOCKING_NOTIFIER_HEAD(memory_bandwidth_notifier);

static struct pm_qos_constraints memory_bw_constraints = {
	.list = PLIST_HEAD_INIT(memory_bw_constraints.list),
	.type = PM_QOS_SUM,
	.notifiers = &memory_bandwidth_notifier,

static struct pm_qos_object memory_bandwidth_pm_qos = {
	.constraints = &memory_bw_constraints,
	.name = "memory_bandwidth",

static struct pm_qos_object *pm_qos_array[] = {

static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
		size_t count, loff_t *f_pos);
static ssize_t pm_qos_power_read(struct file *filp, char __user *buf,
		size_t count, loff_t *f_pos);
static int pm_qos_power_open(struct inode *inode, struct file *filp);
static int pm_qos_power_release(struct inode *inode, struct file *filp);

static const struct file_operations pm_qos_power_fops = {
	.write = pm_qos_power_write,
	.read = pm_qos_power_read,
	.open = pm_qos_power_open,
	.release = pm_qos_power_release,
	.llseek = noop_llseek,

/* unlocked internal variant */

static inline int pm_qos_get_value(struct pm_qos_constraints *c) { struct plist_node *node; int total_value = 0; if (plist_head_empty(&c->list)) return c->no_constraint_value; switch (c->type) { case PM_QOS_MIN: return plist_first(&c->list)->prio; case PM_QOS_MAX: return plist_last(&c->list)->prio; case PM_QOS_SUM: plist_for_each(node, &c->list) total_value += node->prio; return total_value; default: /* runtime check for not using enum */ BUG(); return PM_QOS_DEFAULT_VALUE; } }


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s32 pm_qos_read_value(struct pm_qos_constraints *c) { return c->target_value; }


Tim Chen1173.33%133.33%
Jean Pihet426.67%266.67%

static inline void pm_qos_set_value(struct pm_qos_constraints *c, s32 value) { c->target_value = value; }


Tim Chen1780.95%133.33%
Jean Pihet419.05%266.67%

static inline int pm_qos_get_value(struct pm_qos_constraints *c);
static int pm_qos_dbg_show_requests(struct seq_file *s, void *unused) { struct pm_qos_object *qos = (struct pm_qos_object *)s->private; struct pm_qos_constraints *c; struct pm_qos_request *req; char *type; unsigned long flags; int tot_reqs = 0; int active_reqs = 0; if (IS_ERR_OR_NULL(qos)) { pr_err("%s: bad qos param!\n", __func__); return -EINVAL; } c = qos->constraints; if (IS_ERR_OR_NULL(c)) { pr_err("%s: Bad constraints on qos?\n", __func__); return -EINVAL; } /* Lock to ensure we have a snapshot */ spin_lock_irqsave(&pm_qos_lock, flags); if (plist_head_empty(&c->list)) { seq_puts(s, "Empty!\n"); goto out; } switch (c->type) { case PM_QOS_MIN: type = "Minimum"; break; case PM_QOS_MAX: type = "Maximum"; break; case PM_QOS_SUM: type = "Sum"; break; default: type = "Unknown"; } plist_for_each_entry(req, &c->list, node) { char *state = "Default"; if ((req->node).prio != c->default_value) { active_reqs++; state = "Active"; } tot_reqs++; seq_printf(s, "%d: %d: %s\n", tot_reqs, (req->node).prio, state); } seq_printf(s, "Type=%s, Value=%d, Requests: active=%d / total=%d\n", type, pm_qos_get_value(c), active_reqs, tot_reqs); out: spin_unlock_irqrestore(&pm_qos_lock, flags); return 0; }


Nishanth Menon263100.00%1100.00%

static int pm_qos_dbg_open(struct inode *inode, struct file *file) { return single_open(file, pm_qos_dbg_show_requests, inode->i_private); }


Nishanth Menon28100.00%1100.00%

static const struct file_operations pm_qos_debug_fops = { .open = pm_qos_dbg_open, .read = seq_read, .llseek = seq_lseek, .release = single_release, }; /** * pm_qos_update_target - manages the constraints list and calls the notifiers * if needed * @c: constraints data struct * @node: request to add to the list, to update or to remove * @action: action to take on the constraints list * @value: value of the request to add or update * * This function returns 1 if the aggregated constraint value has changed, 0 * otherwise. */
int pm_qos_update_target(struct pm_qos_constraints *c, struct plist_node *node, enum pm_qos_req_action action, int value) { 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); if (value == PM_QOS_DEFAULT_VALUE) new_value = c->default_value; else new_value = value; switch (action) { case PM_QOS_REMOVE_REQ: plist_del(node, &c->list); break; case PM_QOS_UPDATE_REQ: /* * to change the list, we atomically remove, reinit * with new value and add, then see if the extremal * changed */ plist_del(node, &c->list); case PM_QOS_ADD_REQ: plist_node_init(node, new_value); plist_add(node, &c->list); break; default: /* no action */ ; } curr_value = pm_qos_get_value(c); pm_qos_set_value(c, curr_value); spin_unlock_irqrestore(&pm_qos_lock, flags); trace_pm_qos_update_target(action, prev_value, curr_value); if (prev_value != curr_value) { ret = 1; if (c->notifiers) blocking_notifier_call_chain(c->notifiers, (unsigned long)curr_value, NULL); } else { ret = 0; } return ret; }


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Tim Chen63.00%112.50%

/** * pm_qos_flags_remove_req - Remove device PM QoS flags request. * @pqf: Device PM QoS flags set to remove the request from. * @req: Request to remove from the set. */
static void pm_qos_flags_remove_req(struct pm_qos_flags *pqf, struct pm_qos_flags_request *req) { s32 val = 0; list_del(&req->node); list_for_each_entry(req, &pqf->list, node) val |= req->flags; pqf->effective_flags = val; }


Rafael J. Wysocki49100.00%1100.00%

/** * pm_qos_update_flags - Update a set of PM QoS flags. * @pqf: Set of flags to update. * @req: Request to add to the set, to modify, or to remove from the set. * @action: Action to take on the set. * @val: Value of the request to add or modify. * * Update the given set of PM QoS flags and call notifiers if the aggregate * value has changed. Returns 1 if the aggregate constraint value has changed, * 0 otherwise. */
bool pm_qos_update_flags(struct pm_qos_flags *pqf, struct pm_qos_flags_request *req, enum pm_qos_req_action action, s32 val) { unsigned long irqflags; s32 prev_value, curr_value; spin_lock_irqsave(&pm_qos_lock, irqflags); prev_value = list_empty(&pqf->list) ? 0 : pqf->effective_flags; switch (action) { case PM_QOS_REMOVE_REQ: pm_qos_flags_remove_req(pqf, req); break; case PM_QOS_UPDATE_REQ: pm_qos_flags_remove_req(pqf, req); case PM_QOS_ADD_REQ: req->flags = val; INIT_LIST_HEAD(&req->node); list_add_tail(&req->node, &pqf->list); pqf->effective_flags |= val; break; default: /* no action */ ; } curr_value = list_empty(&pqf->list) ? 0 : pqf->effective_flags; spin_unlock_irqrestore(&pm_qos_lock, irqflags); trace_pm_qos_update_flags(action, prev_value, curr_value); return prev_value != curr_value; }


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Keun-o Park95.62%150.00%

/** * pm_qos_request - returns current system wide qos expectation * @pm_qos_class: identification of which qos value is requested * * This function returns the current target value. */
int pm_qos_request(int pm_qos_class) { return pm_qos_read_value(pm_qos_array[pm_qos_class]->constraints); }


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Tim Chen210.53%120.00%
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int pm_qos_request_active(struct pm_qos_request *req) { return req->pm_qos_class != 0; }


James Bottomley1694.12%150.00%
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static void __pm_qos_update_request(struct pm_qos_request *req, s32 new_value) { trace_pm_qos_update_request(req->pm_qos_class, new_value); if (new_value != req->node.prio) pm_qos_update_target( pm_qos_array[req->pm_qos_class]->constraints, &req->node, PM_QOS_UPDATE_REQ, new_value); }


Stephen Boyd54100.00%1100.00%

/** * pm_qos_work_fn - the timeout handler of pm_qos_update_request_timeout * @work: work struct for the delayed work (timeout) * * This cancels the timeout request by falling back to the default at timeout. */
static void pm_qos_work_fn(struct work_struct *work) { struct pm_qos_request *req = container_of(to_delayed_work(work), struct pm_qos_request, work); __pm_qos_update_request(req, PM_QOS_DEFAULT_VALUE); }


MyungJoo Ham3597.22%150.00%
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/** * pm_qos_add_request - inserts new qos request into the list * @req: pointer to a preallocated handle * @pm_qos_class: identifies which list of qos request to use * @value: defines the qos request * * This function inserts a new entry in the pm_qos_class list of requested qos * performance characteristics. It recomputes the aggregate QoS expectations * for the pm_qos_class of parameters and initializes the pm_qos_request * handle. Caller needs to save this handle for later use in updates and * removal. */
void pm_qos_add_request(struct pm_qos_request *req, int pm_qos_class, s32 value) { if (!req) /*guard against callers passing in null */ return; if (pm_qos_request_active(req)) { WARN(1, KERN_ERR "pm_qos_add_request() called for already added request\n"); return; } req->pm_qos_class = pm_qos_class; INIT_DELAYED_WORK(&req->work, pm_qos_work_fn); trace_pm_qos_add_request(pm_qos_class, value); pm_qos_update_target(pm_qos_array[pm_qos_class]->constraints, &req->node, PM_QOS_ADD_REQ, value); }


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EXPORT_SYMBOL_GPL(pm_qos_add_request); /** * pm_qos_update_request - modifies an existing qos request * @req : handle to list element holding a pm_qos request to use * @value: defines the qos request * * Updates an existing qos request for the pm_qos_class of parameters along * with updating the target pm_qos_class value. * * Attempts are made to make this code callable on hot code paths. */
void pm_qos_update_request(struct pm_qos_request *req, s32 new_value) { if (!req) /*guard against callers passing in null */ return; if (!pm_qos_request_active(req)) { WARN(1, KERN_ERR "pm_qos_update_request() called for unknown object\n"); return; } cancel_delayed_work_sync(&req->work); __pm_qos_update_request(req, new_value); }


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Jean Pihet59.26%220.00%
Keun-o Park23.70%110.00%
Stephen Boyd11.85%110.00%

EXPORT_SYMBOL_GPL(pm_qos_update_request); /** * pm_qos_update_request_timeout - modifies an existing qos request temporarily. * @req : handle to list element holding a pm_qos request to use * @new_value: defines the temporal qos request * @timeout_us: the effective duration of this qos request in usecs. * * After timeout_us, this qos request is cancelled automatically. */
void pm_qos_update_request_timeout(struct pm_qos_request *req, s32 new_value, unsigned long timeout_us) { if (!req) return; if (WARN(!pm_qos_request_active(req), "%s called for unknown object.", __func__)) return; cancel_delayed_work_sync(&req->work); trace_pm_qos_update_request_timeout(req->pm_qos_class, new_value, timeout_us); if (new_value != req->node.prio) pm_qos_update_target( pm_qos_array[req->pm_qos_class]->constraints, &req->node, PM_QOS_UPDATE_REQ, new_value); schedule_delayed_work(&req->work, usecs_to_jiffies(timeout_us)); }


MyungJoo Ham9189.22%150.00%
Keun-o Park1110.78%150.00%

/** * 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 for the pm_qos_class. Call this * on slow code paths. */
void pm_qos_remove_request(struct pm_qos_request *req) { if (!req) /*guard against callers passing in null */ return; /* silent return to keep pcm code cleaner */ if (!pm_qos_request_active(req)) { WARN(1, KERN_ERR "pm_qos_remove_request() called for unknown object\n"); return; } cancel_delayed_work_sync(&req->work); trace_pm_qos_remove_request(req->pm_qos_class, PM_QOS_DEFAULT_VALUE); pm_qos_update_target(pm_qos_array[req->pm_qos_class]->constraints, &req->node, PM_QOS_REMOVE_REQ, PM_QOS_DEFAULT_VALUE); memset(req, 0, sizeof(*req)); }


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EXPORT_SYMBOL_GPL(pm_qos_remove_request); /** * pm_qos_add_notifier - sets notification entry for changes to target value * @pm_qos_class: identifies which qos target changes should be notified. * @notifier: notifier block managed by caller. * * will register the notifier into a notification chain that gets called * upon changes to the pm_qos_class target value. */
int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier) { int retval; retval = blocking_notifier_chain_register( pm_qos_array[pm_qos_class]->constraints->notifiers, notifier); return retval; }


Mark Gross3394.29%150.00%
Jean Pihet25.71%150.00%

EXPORT_SYMBOL_GPL(pm_qos_add_notifier); /** * pm_qos_remove_notifier - deletes notification entry from chain. * @pm_qos_class: identifies which qos target changes are notified. * @notifier: notifier block to be removed. * * will remove the notifier from the notification chain that gets called * upon changes to the pm_qos_class target value. */
int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier) { int retval; retval = blocking_notifier_chain_unregister( pm_qos_array[pm_qos_class]->constraints->notifiers, notifier); return retval; }


Mark Gross3394.29%150.00%
Jean Pihet25.71%150.00%

EXPORT_SYMBOL_GPL(pm_qos_remove_notifier); /* User space interface to PM QoS classes via misc devices */
static int register_pm_qos_misc(struct pm_qos_object *qos, struct dentry *d) { qos->pm_qos_power_miscdev.minor = MISC_DYNAMIC_MINOR; qos-> = qos->name; qos->pm_qos_power_miscdev.fops = &pm_qos_power_fops; if (d) { (void)debugfs_create_file(qos->name, S_IRUGO, d, (void *)qos, &pm_qos_debug_fops); } return misc_register(&qos->pm_qos_power_miscdev); }


Jean Pihet4758.02%150.00%
Nishanth Menon3441.98%150.00%

static int find_pm_qos_object_by_minor(int minor) { int pm_qos_class; for (pm_qos_class = PM_QOS_CPU_DMA_LATENCY; pm_qos_class < PM_QOS_NUM_CLASSES; pm_qos_class++) { if (minor == pm_qos_array[pm_qos_class]->pm_qos_power_miscdev.minor) return pm_qos_class; } return -1; }


Jean Pihet4697.87%150.00%
Keun-o Park12.13%150.00%

static int pm_qos_power_open(struct inode *inode, struct file *filp) { long pm_qos_class; pm_qos_class = find_pm_qos_object_by_minor(iminor(inode)); if (pm_qos_class >= PM_QOS_CPU_DMA_LATENCY) { struct pm_qos_request *req = kzalloc(sizeof(*req), GFP_KERNEL); if (!req) return -ENOMEM; pm_qos_add_request(req, pm_qos_class, PM_QOS_DEFAULT_VALUE); filp->private_data = req; return 0; } return -EPERM; }


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James Bottomley2934.52%116.67%
David Alan Gilbert22.38%116.67%
Keun-o Park11.19%116.67%
Jean Pihet11.19%116.67%

static int pm_qos_power_release(struct inode *inode, struct file *filp) { struct pm_qos_request *req; req = filp->private_data; pm_qos_remove_request(req); kfree(req); return 0; }


Mark Gross3382.50%240.00%
James Bottomley512.50%120.00%
Jonathan Corbet12.50%120.00%
Jean Pihet12.50%120.00%

static ssize_t pm_qos_power_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos) { s32 value; unsigned long flags; struct pm_qos_request *req = filp->private_data; if (!req) return -EINVAL; if (!pm_qos_request_active(req)) return -EINVAL; spin_lock_irqsave(&pm_qos_lock, flags); value = pm_qos_get_value(pm_qos_array[req->pm_qos_class]->constraints); spin_unlock_irqrestore(&pm_qos_lock, flags); return simple_read_from_buffer(buf, count, f_pos, &value, sizeof(s32)); }


Thomas Renninger9688.89%133.33%
Jean Pihet1211.11%266.67%

static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf, size_t count, loff_t *f_pos) { s32 value; struct pm_qos_request *req; if (count == sizeof(s32)) { if (copy_from_user(&value, buf, sizeof(s32))) return -EFAULT; } else { int ret; ret = kstrtos32_from_user(buf, count, 16, &value); if (ret) return ret; } req = filp->private_data; pm_qos_update_request(req, value); return count; }


Mark Gross8681.90%233.33%
Rafael J. Wysocki87.62%116.67%
Andy Shevchenko65.71%116.67%
Jean Pihet43.81%116.67%
Jonathan Corbet10.95%116.67%

static int __init pm_qos_power_init(void) { int ret = 0; int i; struct dentry *d; BUILD_BUG_ON(ARRAY_SIZE(pm_qos_array) != PM_QOS_NUM_CLASSES); d = debugfs_create_dir("pm_qos", NULL); if (IS_ERR_OR_NULL(d)) d = NULL; for (i = PM_QOS_CPU_DMA_LATENCY; i < PM_QOS_NUM_CLASSES; i++) { ret = register_pm_qos_misc(pm_qos_array[i], d); if (ret < 0) { pr_err("%s: %s setup failed\n", __func__, pm_qos_array[i]->name); return ret; } } return ret; }


Mark Gross4239.25%120.00%
Alex Frid3330.84%120.00%
Nishanth Menon2725.23%120.00%
Joe Perches43.74%120.00%
Keun-o Park10.93%120.00%


Overall Contributors

Mark Gross67827.07%38.57%
Nishanth Menon39715.85%12.86%
Jean Pihet33913.53%514.29%
Rafael J. Wysocki2489.90%411.43%
James Bottomley2299.14%25.71%
MyungJoo Ham1546.15%12.86%
Thomas Renninger1234.91%12.86%
Tomeu Vizoso993.95%12.86%
Stephen Boyd562.24%12.86%
Tim Chen552.20%12.86%
Keun-o Park532.12%38.57%
Alex Frid331.32%12.86%
John Kacur70.28%12.86%
Andy Shevchenko60.24%12.86%
Dominik Brodowski50.20%12.86%
Arnd Bergmann50.20%12.86%
Joe Perches40.16%12.86%
Paul Gortmaker30.12%12.86%
Luis Gonzalez Fernandez30.12%12.86%
Jonathan Corbet20.08%12.86%
Colin Cross20.08%12.86%
Richard Hughes20.08%12.86%
David Alan Gilbert20.08%12.86%
Directory: kernel/power
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