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PM / QoS: Fix device resume latency PM QoS 

The special value of 0 for device resume latency PM QoS means
"no restriction", but there are two problems with that.

First, device resume latency PM QoS requests with 0 as the
value are always put in front of requests with positive
values in the priority lists used internally by the PM QoS
framework, causing 0 to be chosen as an effective constraint
value.  However, that 0 is then interpreted as "no restriction"
effectively overriding the other requests with specific
restrictions which is incorrect.

Second, the users of device resume latency PM QoS have no
way to specify that *any* resume latency at all should be
avoided, which is an artificial limitation in general.

To address these issues, modify device resume latency PM QoS to
use S32_MAX as the "no constraint" value and 0 as the "no
latency at all" one and rework its users (the cpuidle menu
governor, the genpd QoS governor and the runtime PM framework)
to follow these changes.

Also add a special "n/a" value to the corresponding user space I/F
to allow user space to indicate that it cannot accept any resume
latencies at all for the given device.

Fixes: 85dc0b8a40 (PM / QoS: Make it possible to expose PM QoS latency constraints)
Link: https://bugzilla.kernel.org/show_bug.cgi?id=197323
Reported-by: Reinette Chatre <reinette.chatre@intel.com>
Tested-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Alex Shi <alex.shi@linaro.org>
Cc: All applicable <stable@vger.kernel.org>
zero-colors
Rafael J. Wysocki 2017-10-24 15:20:45 +02:00
parent bb176f6709
commit 0cc2b4e5a0
8 changed files with 63 additions and 35 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
Documentation/ABI/testing/sysfs-devices-power
View File

@ -211,7 +211,9 @@ Description:
device, after it has been suspended at run time, from a resume
request to the moment the device will be ready to process I/O,
in microseconds. If it is equal to 0, however, this means that
the PM QoS resume latency may be arbitrary.
the PM QoS resume latency may be arbitrary and the special value
"n/a" means that user space cannot accept any resume latency at
all for the given device.
Not all drivers support this attribute. If it isn't supported,
it is not present.

3
drivers/base/cpu.c
View File

@ -377,7 +377,8 @@ int register_cpu(struct cpu *cpu, int num)
per_cpu(cpu_sys_devices, num) = &cpu->dev;
register_cpu_under_node(num, cpu_to_node(num));
dev_pm_qos_expose_latency_limit(&cpu->dev, 0);
dev_pm_qos_expose_latency_limit(&cpu->dev,
PM_QOS_RESUME_LATENCY_NO_CONSTRAINT);
return 0;
}

53
drivers/base/power/domain_governor.c
View File

@ -14,23 +14,20 @@
static int dev_update_qos_constraint(struct device *dev, void *data)
{
s64 *constraint_ns_p = data;
s32 constraint_ns = -1;
s64 constraint_ns = -1;
if (dev->power.subsys_data && dev->power.subsys_data->domain_data)
constraint_ns = dev_gpd_data(dev)->td.effective_constraint_ns;
if (constraint_ns < 0) {
if (constraint_ns < 0)
constraint_ns = dev_pm_qos_read_value(dev);
constraint_ns *= NSEC_PER_USEC;
}
if (constraint_ns == 0)
if (constraint_ns == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT)
return 0;
/*
* constraint_ns cannot be negative here, because the device has been
* suspended.
*/
if (constraint_ns < *constraint_ns_p || *constraint_ns_p == 0)
constraint_ns *= NSEC_PER_USEC;
if (constraint_ns < *constraint_ns_p || *constraint_ns_p < 0)
*constraint_ns_p = constraint_ns;
return 0;
@ -63,10 +60,14 @@ static bool default_suspend_ok(struct device *dev)
spin_unlock_irqrestore(&dev->power.lock, flags);
if (constraint_ns < 0)
if (constraint_ns == 0)
return false;
constraint_ns *= NSEC_PER_USEC;
if (constraint_ns == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT)
constraint_ns = -1;
else
constraint_ns *= NSEC_PER_USEC;
/*
* We can walk the children without any additional locking, because
* they all have been suspended at this point and their
@ -76,14 +77,19 @@ static bool default_suspend_ok(struct device *dev)
device_for_each_child(dev, &constraint_ns,
dev_update_qos_constraint);
if (constraint_ns > 0) {
constraint_ns -= td->suspend_latency_ns +
td->resume_latency_ns;
if (constraint_ns == 0)
return false;
if (constraint_ns < 0) {
/* The children have no constraints. */
td->effective_constraint_ns = PM_QOS_RESUME_LATENCY_NO_CONSTRAINT;
td->cached_suspend_ok = true;
} else {
constraint_ns -= td->suspend_latency_ns + td->resume_latency_ns;
if (constraint_ns > 0) {
td->effective_constraint_ns = constraint_ns;
td->cached_suspend_ok = true;
} else {
td->effective_constraint_ns = 0;
}
}
td->effective_constraint_ns = constraint_ns;
td->cached_suspend_ok = constraint_ns >= 0;
/*
* The children have been suspended already, so we don't need to take
@ -145,13 +151,14 @@ static bool __default_power_down_ok(struct dev_pm_domain *pd,
td = &to_gpd_data(pdd)->td;
constraint_ns = td->effective_constraint_ns;
/* default_suspend_ok() need not be called before us. */
if (constraint_ns < 0) {
if (constraint_ns < 0)
constraint_ns = dev_pm_qos_read_value(pdd->dev);
constraint_ns *= NSEC_PER_USEC;
}
if (constraint_ns == 0)
if (constraint_ns == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT)
continue;
constraint_ns *= NSEC_PER_USEC;
/*
* constraint_ns cannot be negative here, because the device has
* been suspended.

2
drivers/base/power/qos.c
View File

@ -189,7 +189,7 @@ static int dev_pm_qos_constraints_allocate(struct device *dev)
plist_head_init(&c->list);
c->target_value = PM_QOS_RESUME_LATENCY_DEFAULT_VALUE;
c->default_value = PM_QOS_RESUME_LATENCY_DEFAULT_VALUE;
c->no_constraint_value = PM_QOS_RESUME_LATENCY_DEFAULT_VALUE;
c->no_constraint_value = PM_QOS_RESUME_LATENCY_NO_CONSTRAINT;
c->type = PM_QOS_MIN;
c->notifiers = n;

2
drivers/base/power/runtime.c
View File

@ -253,7 +253,7 @@ static int rpm_check_suspend_allowed(struct device *dev)
|| (dev->power.request_pending
&& dev->power.request == RPM_REQ_RESUME))
retval = -EAGAIN;
else if (__dev_pm_qos_read_value(dev) < 0)
else if (__dev_pm_qos_read_value(dev) == 0)
retval = -EPERM;
else if (dev->power.runtime_status == RPM_SUSPENDED)
retval = 1;

25
drivers/base/power/sysfs.c
View File

@ -218,7 +218,14 @@ static ssize_t pm_qos_resume_latency_show(struct device *dev,
struct device_attribute *attr,
char *buf)
{
return sprintf(buf, "%d\n", dev_pm_qos_requested_resume_latency(dev));
s32 value = dev_pm_qos_requested_resume_latency(dev);
if (value == 0)
return sprintf(buf, "n/a\n");
else if (value == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT)
value = 0;
return sprintf(buf, "%d\n", value);
}
static ssize_t pm_qos_resume_latency_store(struct device *dev,
@ -228,11 +235,21 @@ static ssize_t pm_qos_resume_latency_store(struct device *dev,
s32 value;
int ret;
if (kstrtos32(buf, 0, &value))
return -EINVAL;
if (!kstrtos32(buf, 0, &value)) {
/*
* Prevent users from writing negative or "no constraint" values
* directly.
*/
if (value < 0 || value == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT)
return -EINVAL;
if (value < 0)
if (value == 0)
value = PM_QOS_RESUME_LATENCY_NO_CONSTRAINT;
} else if (!strcmp(buf, "n/a") || !strcmp(buf, "n/a\n")) {
value = 0;
} else {
return -EINVAL;
}
ret = dev_pm_qos_update_request(dev->power.qos->resume_latency_req,
value);

4
drivers/cpuidle/governors/menu.c
View File

@ -298,8 +298,8 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
data->needs_update = 0;
}
/* resume_latency is 0 means no restriction */
if (resume_latency && resume_latency < latency_req)
if (resume_latency < latency_req &&
resume_latency != PM_QOS_RESUME_LATENCY_NO_CONSTRAINT)
latency_req = resume_latency;
/* Special case when user has set very strict latency requirement */

5
include/linux/pm_qos.h
View File

@ -27,16 +27,17 @@ enum pm_qos_flags_status {
PM_QOS_FLAGS_ALL,
};
#define PM_QOS_DEFAULT_VALUE -1
#define PM_QOS_DEFAULT_VALUE (-1)
#define PM_QOS_LATENCY_ANY S32_MAX
#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_MEMORY_BANDWIDTH_DEFAULT_VALUE 0
#define PM_QOS_RESUME_LATENCY_DEFAULT_VALUE 0
#define PM_QOS_RESUME_LATENCY_NO_CONSTRAINT PM_QOS_LATENCY_ANY
#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)