8 files changed, 63 insertions, 35 deletions

diff --git a/Documentation/ABI/testing/sysfs-devices-power b/Documentation/ABI/testing/sysfs-devices-power
index 676fdf5f2a99..5cbb6f038615 100644
--- a/Documentation/ABI/testing/sysfs-devices-power
+++ b/Documentation/ABI/testing/sysfs-devices-power
@@ -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.
diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index 321cd7b4d817..227bac5f1191 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -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;
 }
diff --git a/drivers/base/power/domain_governor.c b/drivers/base/power/domain_governor.c
index 281f949c5ffe..51751cc8c9e6 100644
--- a/drivers/base/power/domain_governor.c
+++ b/drivers/base/power/domain_governor.c
@@ -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.
diff --git a/drivers/base/power/qos.c b/drivers/base/power/qos.c
index 277d43a83f53..7d29286d9313 100644
--- a/drivers/base/power/qos.c
+++ b/drivers/base/power/qos.c
@@ -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;
 
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 156ab57bca77..632077f05c57 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);
diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index 48eaf2879228..aa390404e85f 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -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 */
diff --git a/include/linux/pm_qos.h b/include/linux/pm_qos.h
index 032b55909145..6737a8c9e8c6 100644
--- a/include/linux/pm_qos.h
+++ b/include/linux/pm_qos.h
@@ -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)