[PATCH 08/10] PM / Domains: Add support for removing PM domains

[Jon Hunter <jonathanh@nvidia.com>]

The genpd framework allows users to add PM domains via the pm_genpd_init()
function, however, there is no corresponding function to remove a PM
domain. For most devices this may be fine as the PM domains are never
removed, however, for devices that wish to populate the PM domains from
within a driver, having the ability to remove a PM domain if the probing
of the device fails or the driver is unloaded is necessary.

Add the function pm_genpd_remove() to remove a PM domain by referencing
it's generic_pm_domain structure.

PM domains can only be removed if they are not a parent domain to
another PM domain and have no devices associated with them.

Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
---
 drivers/base/power/domain.c | 46 +++++++++++++++++++++++++++++++++++++++++++++
 include/linux/pm_domain.h   |  5 +++++
 2 files changed, 51 insertions(+)

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 7ce4608bbbe0..72b973539205 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -1356,6 +1356,52 @@ int pm_genpd_init(struct generic_pm_domain *genpd,
 }
 EXPORT_SYMBOL_GPL(pm_genpd_init);
 
+/**
+ * pm_genpd_remove - Remove a generic I/O PM domain
+ * @genpd: Pointer to PM domain that is to be removed.
+ *
+ * To remove the PM domain, this function:
+ *  - Removes the PM domain as a subdomain to any parent domains,
+ *    if it was added.
+ *  - Removes the PM domain from the list of registered PM domains.
+ *
+ * The PM domain will only be removed, if it is not a parent to any
+ * other PM domain and has no devices associated with it.
+ */
+int pm_genpd_remove(struct generic_pm_domain *genpd)
+{
+	struct gpd_link *l, *link;
+	int ret = 0;
+
+	if (IS_ERR_OR_NULL(genpd))
+		return -EINVAL;
+
+	mutex_lock(&gpd_list_lock);
+	mutex_lock(&genpd->lock);
+
+	if (!list_empty(&genpd->master_links) || genpd->device_count) {
+		mutex_unlock(&genpd->lock);
+		mutex_unlock(&gpd_list_lock);
+		pr_err("%s: unable to remove %s\n", __func__, genpd->name);
+		return -EBUSY;
+	}
+
+	list_for_each_entry_safe(link, l, &genpd->slave_links, slave_node) {
+		list_del(&link->master_node);
+		list_del(&link->slave_node);
+		kfree(link);
+	}
+
+	list_del(&genpd->gpd_list_node);
+	mutex_unlock(&genpd->lock);
+	cancel_work_sync(&genpd->power_off_work);
+	mutex_unlock(&gpd_list_lock);
+	pr_debug("%s: removed %s\n", __func__, genpd->name);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(pm_genpd_remove);
+
 #ifdef CONFIG_PM_GENERIC_DOMAINS_OF
 
 typedef struct generic_pm_domain *(*genpd_xlate_t)(struct of_phandle_args *args,
diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
index f103869db443..fbdc5c4588ef 100644
--- a/include/linux/pm_domain.h
+++ b/include/linux/pm_domain.h
@@ -128,6 +128,7 @@ extern int pm_genpd_remove_subdomain(struct generic_pm_domain *genpd,
 				     struct generic_pm_domain *target);
 extern int pm_genpd_init(struct generic_pm_domain *genpd,
 			 struct dev_power_governor *gov, bool is_off);
+extern int pm_genpd_remove(struct generic_pm_domain *genpd);
 
 extern struct dev_power_governor simple_qos_governor;
 extern struct dev_power_governor pm_domain_always_on_gov;
@@ -163,6 +164,10 @@ static inline int pm_genpd_init(struct generic_pm_domain *genpd,
 {
 	return -ENOSYS;
 }
+static inline int pm_genpd_remove(struct generic_pm_domain *genpd)
+{
+	return -ENOTSUPP;
+}
 #endif
 
 static inline int pm_genpd_add_device(struct generic_pm_domain *genpd,
-- 
2.1.4