Revert "PM / QoS: Fix device resume latency PM QoS"

This reverts commit 0cc2b4e (PM / QoS: Fix device resume latency PM
QoS) as it introduced regressions on multiple systems and the fix-up
in commit 2a9a86d (PM / QoS: Fix default runtime_pm device resume
latency) does not address all of them.

The original problem that commit 0cc2b4e was attempting to fix
will be addressed later.

Fixes: 0cc2b4e (PM / QoS: Fix device resume latency PM QoS)
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Author: rafaeljw

Documentation/ABI/testing/sysfs-devices-power

@@ -211,9 +211,7 @@ 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 and the special value
-		"n/a" means that user space cannot accept any resume latency at
-		all for the given device.
+		the PM QoS resume latency may be arbitrary.
 
 		Not all drivers support this attribute.  If it isn't supported,
 		it is not present.

drivers/base/cpu.c

@@ -377,8 +377,7 @@ 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,
-					PM_QOS_RESUME_LATENCY_NO_CONSTRAINT);
+	dev_pm_qos_expose_latency_limit(&cpu->dev, 0);
 
 	return 0;
 }

drivers/base/power/domain_governor.c

@@ -14,20 +14,23 @@
 static int dev_update_qos_constraint(struct device *dev, void *data)
 {
 	s64 *constraint_ns_p = data;
-	s64 constraint_ns = -1;
+	s32 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);
-
-	if (constraint_ns == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT)
+		constraint_ns *= NSEC_PER_USEC;
+	}
+	if (constraint_ns == 0)
 		return 0;
 
-	constraint_ns *= NSEC_PER_USEC;
-
-	if (constraint_ns < *constraint_ns_p || *constraint_ns_p < 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_p = constraint_ns;
 
 	return 0;
@@ -60,14 +63,10 @@ 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;
 
-	if (constraint_ns == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT)
-		constraint_ns = -1;
-	else
-		constraint_ns *= NSEC_PER_USEC;
-
+	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
@@ -77,19 +76,14 @@ static bool default_suspend_ok(struct device *dev)
 		device_for_each_child(dev, &constraint_ns,
 				      dev_update_qos_constraint);
 
-	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;
-		}
+	if (constraint_ns > 0) {
+		constraint_ns -= td->suspend_latency_ns +
+				td->resume_latency_ns;
+		if (constraint_ns == 0)
+			return false;
 	}
+	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
@@ -151,14 +145,13 @@ 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);
-
-		if (constraint_ns == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT)
+			constraint_ns *= NSEC_PER_USEC;
+		}
+		if (constraint_ns == 0)
 			continue;
 
-		constraint_ns *= NSEC_PER_USEC;
-
 		/*
 		 * constraint_ns cannot be negative here, because the device has
 		 * been suspended.

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_NO_CONSTRAINT;
+	c->no_constraint_value = PM_QOS_RESUME_LATENCY_DEFAULT_VALUE;
 	c->type = PM_QOS_MIN;
 	c->notifiers = n;
 

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;

drivers/base/power/sysfs.c

@@ -218,14 +218,7 @@ static ssize_t pm_qos_resume_latency_show(struct device *dev,
 					  struct device_attribute *attr,
 					  char *buf)
 {
-	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);
+	return sprintf(buf, "%d\n", dev_pm_qos_requested_resume_latency(dev));
 }
 
 static ssize_t pm_qos_resume_latency_store(struct device *dev,
@@ -235,21 +228,11 @@ static ssize_t pm_qos_resume_latency_store(struct device *dev,
 	s32 value;
 	int ret;
 
-	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 (kstrtos32(buf, 0, &value))
+		return -EINVAL;
 
-		if (value == 0)
-			value = PM_QOS_RESUME_LATENCY_NO_CONSTRAINT;
-	} else if (!strcmp(buf, "n/a") || !strcmp(buf, "n/a\n")) {
-		value = 0;
-	} else {
+	if (value < 0)
 		return -EINVAL;
-	}
 
 	ret = dev_pm_qos_update_request(dev->power.qos->resume_latency_req,
 					value);

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;
 	}
 
-	if (resume_latency < latency_req &&
-	    resume_latency != PM_QOS_RESUME_LATENCY_NO_CONSTRAINT)
+	/* resume_latency is 0 means no restriction */
+	if (resume_latency && resume_latency < latency_req)
 		latency_req = resume_latency;
 
 	/* Special case when user has set very strict latency requirement */

include/linux/pm_qos.h

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