PM / Domains: Allow a better error handling of dev_pm_domain_attach()

The callers of dev_pm_domain_attach() currently checks the returned error
code for -EPROBE_DEFER and needs to ignore other error codes. This is an
unnecessary limitation, which also leads to a rather strange behaviour in
the error path.

Address this limitation, by changing the return codes from
acpi_dev_pm_attach() and genpd_dev_pm_attach(). More precisely, let them
return 0, when no PM domain is needed for the device and then return 1, in
case the device was successfully attached to its PM domain. In this way,
dev_pm_domain_attach(), gets a better understanding of what happens in the
attach attempts and also allowing its caller to better act on real errors
codes.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/device_pm.c

@@ -1257,7 +1257,7 @@ int acpi_dev_pm_attach(struct device *dev, bool power_on)
 	struct acpi_device *adev = ACPI_COMPANION(dev);
 
 	if (!adev)
-		return -ENODEV;
+		return 0;
 
 	/*
 	 * Only attach the power domain to the first device if the
@@ -1265,7 +1265,7 @@ int acpi_dev_pm_attach(struct device *dev, bool power_on)
 	 * management twice.
 	 */
 	if (!acpi_device_is_first_physical_node(adev, dev))
-		return -EBUSY;
+		return 0;
 
 	acpi_add_pm_notifier(adev, dev, acpi_pm_notify_work_func);
 	dev_pm_domain_set(dev, &acpi_general_pm_domain);
@@ -1275,7 +1275,7 @@ int acpi_dev_pm_attach(struct device *dev, bool power_on)
 	}
 
 	dev->pm_domain->detach = acpi_dev_pm_detach;
-	return 0;
+	return 1;
 }
 EXPORT_SYMBOL_GPL(acpi_dev_pm_attach);
 #endif /* CONFIG_PM */

drivers/base/power/common.c

@@ -98,7 +98,8 @@ EXPORT_SYMBOL_GPL(dev_pm_put_subsys_data);
  * Callers must ensure proper synchronization of this function with power
  * management callbacks.
  *
- * Returns 0 on successfully attached PM domain or negative error code.
+ * Returns 0 on successfully attached PM domain and when it found that the
+ * device don't need a PM domain, else a negative error code.
  */
 int dev_pm_domain_attach(struct device *dev, bool power_on)
 {
@@ -108,10 +109,10 @@ int dev_pm_domain_attach(struct device *dev, bool power_on)
 		return -EEXIST;
 
 	ret = acpi_dev_pm_attach(dev, power_on);
-	if (ret)
+	if (!ret)
 		ret = genpd_dev_pm_attach(dev);
 
-	return ret;
+	return ret < 0 ? ret : 0;
 }
 EXPORT_SYMBOL_GPL(dev_pm_domain_attach);
 

drivers/base/power/domain.c

@@ -2180,10 +2180,11 @@ static void genpd_dev_pm_sync(struct device *dev)
  * Parse device's OF node to find a PM domain specifier. If such is found,
  * attaches the device to retrieved pm_domain ops.
  *
- * Returns 0 on successfully attached PM domain or negative error code. Note
- * that if a power-domain exists for the device, but it cannot be found or
- * turned on, then return -EPROBE_DEFER to ensure that the device is not
- * probed and to re-try again later.
+ * Returns 1 on successfully attached PM domain, 0 when the device don't need a
+ * PM domain or a negative error code in case of failures. Note that if a
+ * power-domain exists for the device, but it cannot be found or turned on,
+ * then return -EPROBE_DEFER to ensure that the device is not probed and to
+ * re-try again later.
  */
 int genpd_dev_pm_attach(struct device *dev)
 {
@@ -2192,12 +2193,12 @@ int genpd_dev_pm_attach(struct device *dev)
 	int ret;
 
 	if (!dev->of_node)
-		return -ENODEV;
+		return 0;
 
 	ret = of_parse_phandle_with_args(dev->of_node, "power-domains",
 					"#power-domain-cells", 0, &pd_args);
 	if (ret < 0)
-		return ret;
+		return 0;
 
 	mutex_lock(&gpd_list_lock);
 	pd = genpd_get_from_provider(&pd_args);
@@ -2218,7 +2219,7 @@ int genpd_dev_pm_attach(struct device *dev)
 		if (ret != -EPROBE_DEFER)
 			dev_err(dev, "failed to add to PM domain %s: %d",
 				pd->name, ret);
-		goto out;
+		return ret;
 	}
 
 	dev->pm_domain->detach = genpd_dev_pm_detach;
@@ -2230,8 +2231,8 @@ int genpd_dev_pm_attach(struct device *dev)
 
 	if (ret)
 		genpd_remove_device(pd, dev);
-out:
-	return ret ? -EPROBE_DEFER : 0;
+
+	return ret ? -EPROBE_DEFER : 1;
 }
 EXPORT_SYMBOL_GPL(genpd_dev_pm_attach);
 

include/linux/acpi.h

@@ -899,7 +899,7 @@ static inline int acpi_subsys_runtime_suspend(struct device *dev) { return 0; }
 static inline int acpi_subsys_runtime_resume(struct device *dev) { return 0; }
 static inline int acpi_dev_pm_attach(struct device *dev, bool power_on)
 {
-	return -ENODEV;
+	return 0;
 }
 #endif
 

include/linux/pm_domain.h

@@ -280,7 +280,7 @@ static inline int of_genpd_parse_idle_states(struct device_node *dn,
 
 static inline int genpd_dev_pm_attach(struct device *dev)
 {
-	return -ENODEV;
+	return 0;
 }
 
 static inline
@@ -297,7 +297,7 @@ extern void dev_pm_domain_set(struct device *dev, struct dev_pm_domain *pd);
 #else
 static inline int dev_pm_domain_attach(struct device *dev, bool power_on)
 {
-	return -ENODEV;
+	return 0;
 }
 static inline void dev_pm_domain_detach(struct device *dev, bool power_off) {}
 static inline void dev_pm_domain_set(struct device *dev,