5 files changed, 43 insertions, 31 deletions

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 679c79545e42..24e39ce27bd8 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -1326,7 +1326,7 @@ static struct generic_pm_domain_data *genpd_alloc_dev_data(struct device *dev,
 
 	gpd_data->base.dev = dev;
 	gpd_data->td.constraint_changed = true;
-	gpd_data->td.effective_constraint_ns = 0;
+	gpd_data->td.effective_constraint_ns = PM_QOS_RESUME_LATENCY_NO_CONSTRAINT_NS;
 	gpd_data->nb.notifier_call = genpd_dev_pm_qos_notifier;
 
 	spin_lock_irq(&dev->power.lock);
diff --git a/drivers/base/power/domain_governor.c b/drivers/base/power/domain_governor.c
index e4cca8adab32..99896fbf18e4 100644
--- a/drivers/base/power/domain_governor.c
+++ b/drivers/base/power/domain_governor.c
@@ -33,15 +33,10 @@ static int dev_update_qos_constraint(struct device *dev, void *data)
 		 * known at this point anyway).
 		 */
 		constraint_ns = dev_pm_qos_read_value(dev);
-		if (constraint_ns > 0)
-			constraint_ns *= NSEC_PER_USEC;
+		constraint_ns *= NSEC_PER_USEC;
 	}
 
-	/* 0 means "no constraint" */
-	if (constraint_ns == 0)
-		return 0;
-
-	if (constraint_ns < *constraint_ns_p || *constraint_ns_p == 0)
+	if (constraint_ns < *constraint_ns_p)
 		*constraint_ns_p = constraint_ns;
 
 	return 0;
@@ -69,12 +64,12 @@ static bool default_suspend_ok(struct device *dev)
 	}
 	td->constraint_changed = false;
 	td->cached_suspend_ok = false;
-	td->effective_constraint_ns = -1;
+	td->effective_constraint_ns = 0;
 	constraint_ns = __dev_pm_qos_read_value(dev);
 
 	spin_unlock_irqrestore(&dev->power.lock, flags);
 
-	if (constraint_ns < 0)
+	if (constraint_ns == 0)
 		return false;
 
 	constraint_ns *= NSEC_PER_USEC;
@@ -87,25 +82,25 @@ static bool default_suspend_ok(struct device *dev)
 		device_for_each_child(dev, &constraint_ns,
 				      dev_update_qos_constraint);
 
-	if (constraint_ns == 0) {
+	if (constraint_ns == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT_NS) {
 		/* "No restriction", so the device is allowed to suspend. */
-		td->effective_constraint_ns = 0;
+		td->effective_constraint_ns = PM_QOS_RESUME_LATENCY_NO_CONSTRAINT_NS;
 		td->cached_suspend_ok = true;
-	} else if (constraint_ns < 0) {
+	} else if (constraint_ns == 0) {
 		/*
 		 * This triggers if one of the children that don't belong to a
-		 * domain has a negative PM QoS constraint and it's better not
-		 * to suspend then.  effective_constraint_ns is negative already
-		 * and cached_suspend_ok is false, so bail out.
+		 * domain has a zero PM QoS constraint and it's better not to
+		 * suspend then.  effective_constraint_ns is zero already and
+		 * cached_suspend_ok is false, so bail out.
 		 */
 		return false;
 	} else {
 		constraint_ns -= td->suspend_latency_ns +
 				td->resume_latency_ns;
 		/*
-		 * effective_constraint_ns is negative already and
-		 * cached_suspend_ok is false, so if the computed value is not
-		 * positive, return right away.
+		 * effective_constraint_ns is zero already and cached_suspend_ok
+		 * is false, so if the computed value is not positive, return
+		 * right away.
 		 */
 		if (constraint_ns <= 0)
 			return false;
@@ -174,13 +169,10 @@ static bool __default_power_down_ok(struct dev_pm_domain *pd,
 		td = &to_gpd_data(pdd)->td;
 		constraint_ns = td->effective_constraint_ns;
 		/*
-		 * Negative values mean "no suspend at all" and this runs only
-		 * when all devices in the domain are suspended, so it must be
-		 * 0 at least.
-		 *
-		 * 0 means "no constraint"
+		 * Zero means "no suspend at all" and this runs only when all
+		 * devices in the domain are suspended, so it must be positive.
 		 */
-		if (constraint_ns == 0)
+		if (constraint_ns == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT_NS)
 			continue;
 
 		if (constraint_ns <= off_on_time_ns)
diff --git a/drivers/base/power/qos.c b/drivers/base/power/qos.c
index 277d43a83f53..3382542b39b7 100644
--- a/drivers/base/power/qos.c
+++ b/drivers/base/power/qos.c
@@ -139,6 +139,9 @@ static int apply_constraint(struct dev_pm_qos_request *req,
 
 	switch(req->type) {
 	case DEV_PM_QOS_RESUME_LATENCY:
+		if (WARN_ON(action != PM_QOS_REMOVE_REQ && value < 0))
+			value = 0;
+
 		ret = pm_qos_update_target(&qos->resume_latency,
 					   &req->data.pnode, action, value);
 		break;
@@ -189,7 +192,7 @@ 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;
 
diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
index 7bcf80fa9ada..13e015905543 100644
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -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;
diff --git a/drivers/base/power/sysfs.c b/drivers/base/power/sysfs.c
index 29bf28fef136..e153e28b1857 100644
--- a/drivers/base/power/sysfs.c
+++ b/drivers/base/power/sysfs.c
@@ -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);