linux/kernel/power/qos.c
Nishanth Menon f5f4eda4c9 PM / QoS: Add debugfs support to view the list of constraints
PM QoS requests are notoriously hard to debug and made even
more so due to their highly dynamic nature. Having visibility
into the internal data representation per constraint allows
us to have much better appreciation of potential issues or
bad usage by drivers in the system.

So introduce for all classes of PM QoS, an entry in
/sys/kernel/debug/pm_qos that shall show all the current
requests as well as the snapshot of the value these requests
boil down to. For example:
==> /sys/kernel/debug/pm_qos/cpu_dma_latency <==
1: 4444: Active
2: 2000000000: Default
3: 2000000000: Default
4: 2000000000: Default
Type=Minimum, Value=4444, Requests: active=1 / total=4

==> /sys/kernel/debug/pm_qos/memory_bandwidth <==
Empty!

...

The actual value listed will have their meaning based
on the QoS it is on, the 'Type' indicates what logic
it would use to collate the information - Minimum,
Maximum, or Sum. Value is the collation of all requests.
This interface also compares the values with the defaults
for the QoS class and marks the ones that are
currently active.

Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Dave Gerlach <d-gerlach@ti.com>
Acked-by: Kevin Hilman <khilman@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2015-01-23 22:16:21 +01:00

714 lines
19 KiB
C

/*
* 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 <mgross@linux.intel.com>
*/
/*#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),
.target_value = PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE,
.default_value = PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE,
.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),
.target_value = PM_QOS_NETWORK_LAT_DEFAULT_VALUE,
.default_value = PM_QOS_NETWORK_LAT_DEFAULT_VALUE,
.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),
.target_value = PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE,
.default_value = PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE,
.no_constraint_value = PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE,
.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),
.target_value = PM_QOS_MEMORY_BANDWIDTH_DEFAULT_VALUE,
.default_value = PM_QOS_MEMORY_BANDWIDTH_DEFAULT_VALUE,
.no_constraint_value = PM_QOS_MEMORY_BANDWIDTH_DEFAULT_VALUE,
.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[] = {
&null_pm_qos,
&cpu_dma_pm_qos,
&network_lat_pm_qos,
&network_throughput_pm_qos,
&memory_bandwidth_pm_qos,
};
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;
}
}
s32 pm_qos_read_value(struct pm_qos_constraints *c)
{
return c->target_value;
}
static inline void pm_qos_set_value(struct pm_qos_constraints *c, s32 value)
{
c->target_value = value;
}
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;
}
static int pm_qos_dbg_open(struct inode *inode, struct file *file)
{
return single_open(file, pm_qos_dbg_show_requests,
inode->i_private);
}
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;
}
/**
* 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;
}
/**
* 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;
}
/**
* 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);
}
EXPORT_SYMBOL_GPL(pm_qos_request);
int pm_qos_request_active(struct pm_qos_request *req)
{
return req->pm_qos_class != 0;
}
EXPORT_SYMBOL_GPL(pm_qos_request_active);
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);
}
/**
* 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);
}
/**
* 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);
}
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);
}
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));
}
/**
* 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));
}
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;
}
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;
}
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->pm_qos_power_miscdev.name = 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);
}
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;
}
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;
}
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;
}
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));
}
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;
}
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) {
printk(KERN_ERR "pm_qos_param: %s setup failed\n",
pm_qos_array[i]->name);
return ret;
}
}
return ret;
}
late_initcall(pm_qos_power_init);