[PATCH v1 2/3] ACPI / PM: Attach ACPI power domain only once

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

From: Mika Westerberg <mika.westerberg@linux.intel.com>

Some devices, like MFD subdevices, share a single ACPI companion device so
that they are able to access their resources and children. However,
currently all these subdevices are attached to the ACPI power domain and
this might cause that the power methods for the companion device get called
more than once.

In order to solve this we attach the ACPI power domain only to the first
physical device that is bound to the ACPI companion device. In case of MFD
devices, this is the parent MFD device itself.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 drivers/acpi/device_pm.c |  8 ++++++++
 drivers/acpi/internal.h  |  2 ++
 drivers/acpi/scan.c      | 46 ++++++++++++++++++++++++++++++++--------------
 3 files changed, 42 insertions(+), 14 deletions(-)

diff --git a/drivers/acpi/device_pm.c b/drivers/acpi/device_pm.c
index 735db11..7d0c7e9 100644
--- a/drivers/acpi/device_pm.c
+++ b/drivers/acpi/device_pm.c
@@ -1103,6 +1103,14 @@ 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 56b321a..2aa8430 100644
--- a/drivers/acpi/internal.h
+++ b/drivers/acpi/internal.h
@@ -96,6 +96,8 @@ 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 bbca783..1beef99 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -188,6 +188,37 @@ static int create_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;
+
+	mutex_lock(&adev->physical_node_lock);
+	if (list_empty(&adev->physical_node_list)) {
+		ret = false;
+	} else {
+		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
@@ -211,7 +242,6 @@ static int create_modalias(struct acpi_device *acpi_dev, char *modalias,
 static bool acpi_companion_match(const struct device *dev)
 {
 	struct acpi_device *adev;
-	bool ret;
 
 	adev = ACPI_COMPANION(dev);
 	if (!adev)
@@ -220,19 +250,7 @@ static bool acpi_companion_match(const struct device *dev)
 	if (list_empty(&adev->pnp.ids))
 		return false;
 
-	mutex_lock(&adev->physical_node_lock);
-	if (list_empty(&adev->physical_node_list)) {
-		ret = false;
-	} else {
-		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;
+	return acpi_device_is_first_physical_node(adev, dev);
 }
 
 /*
-- 
2.1.4