3 files changed, 40 insertions, 16 deletions

diff --git a/drivers/acpi/device_pm.c b/drivers/acpi/device_pm.c
index 717afcdb5f4a..08dc3ec7e892 100644
--- a/drivers/acpi/device_pm.c
+++ b/drivers/acpi/device_pm.c
@@ -1123,6 +1123,14 @@ int acpi_dev_pm_attach(struct device *dev, bool power_on)
         if (dev->pm_domain)
                 return -EEXIST;
 
+        /*
+         * Only attach the power domain to the first device if the
+         * companion is shared by multiple. This is to prevent doing power
+         * management twice.
+         */
+        if (!acpi_device_is_first_physical_node(adev, dev))
+                return -EBUSY;
+
         acpi_add_pm_notifier(adev, dev, acpi_pm_notify_work_func);
         dev->pm_domain = &acpi_general_pm_domain;
         if (power_on) {
diff --git a/drivers/acpi/internal.h b/drivers/acpi/internal.h
index 4683a96932b9..f6aefe984941 100644
--- a/drivers/acpi/internal.h
+++ b/drivers/acpi/internal.h
@@ -97,6 +97,8 @@ void acpi_device_add_finalize(struct acpi_device *device);
 void acpi_free_pnp_ids(struct acpi_device_pnp *pnp);
 bool acpi_device_is_present(struct acpi_device *adev);
 bool acpi_device_is_battery(struct acpi_device *adev);
+bool acpi_device_is_first_physical_node(struct acpi_device *adev,
+                                        const struct device *dev);
 
 /* --------------------------------------------------------------------------
                                   Power Resource
diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index ec256352f423..89ff6d2eef8a 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -226,6 +226,35 @@ static int create_of_modalias(struct acpi_device *acpi_dev, char *modalias,
         return len;
 }
 
+/**
+ * acpi_device_is_first_physical_node - Is given dev first physical node
+ * @adev: ACPI companion device
+ * @dev: Physical device to check
+ *
+ * Function checks if given @dev is the first physical devices attached to
+ * the ACPI companion device. This distinction is needed in some cases
+ * where the same companion device is shared between many physical devices.
+ *
+ * Note that the caller have to provide valid @adev pointer.
+ */
+bool acpi_device_is_first_physical_node(struct acpi_device *adev,
+                                        const struct device *dev)
+{
+        bool ret = false;
+
+        mutex_lock(&adev->physical_node_lock);
+        if (!list_empty(&adev->physical_node_list)) {
+                const struct acpi_device_physical_node *node;
+
+                node = list_first_entry(&adev->physical_node_list,
+                                        struct acpi_device_physical_node, node);
+                ret = node->dev == dev;
+        }
+        mutex_unlock(&adev->physical_node_lock);
+
+        return ret;
+}
+
 /*
  * acpi_companion_match() - Can we match via ACPI companion device
  * @dev: Device in question
@@ -250,7 +279,6 @@ static int create_of_modalias(struct acpi_device *acpi_dev, char *modalias,
 static struct acpi_device *acpi_companion_match(const struct device *dev)
 {
         struct acpi_device *adev;
-        struct mutex *physical_node_lock;
 
         adev = ACPI_COMPANION(dev);
         if (!adev)
@@ -259,21 +287,7 @@ static struct acpi_device *acpi_companion_match(const struct device *dev)
         if (list_empty(&adev->pnp.ids))
                 return NULL;
 
-        physical_node_lock = &adev->physical_node_lock;
-        mutex_lock(physical_node_lock);
-        if (list_empty(&adev->physical_node_list)) {
-                adev = NULL;
-        } else {
-                const struct acpi_device_physical_node *node;
-
-                node = list_first_entry(&adev->physical_node_list,
-                                        struct acpi_device_physical_node, node);
-                if (node->dev != dev)
-                        adev = NULL;
-        }
-        mutex_unlock(physical_node_lock);
-
-        return adev;
+        return acpi_device_is_first_physical_node(adev, dev) ? adev : NULL;
 }
 
 static int __acpi_device_uevent_modalias(struct acpi_device *adev,