PM / Domains: Add device domain data reference counter

Add a mechanism for counting references to the
struct generic_pm_domain_data object pointed to by
dev->power.subsys_data->domain_data if the device in question
belongs to a generic PM domain.

This change is necessary for a subsequent patch making it possible to
allocate that object from within pm_genpd_add_callbacks(), so that
drivers can attach their PM domain device callbacks to devices before
those devices are added to PM domains.

This patch has been tested on the SH7372 Mackerel board.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

2 files changed, 58 insertions, 26 deletions

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 4b5f090fccb6..45eb3b155b6d 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -297,7 +297,7 @@ static int genpd_dev_pm_qos_notifier(struct notifier_block *nb,
 
                 pdd = dev->power.subsys_data ?
                                 dev->power.subsys_data->domain_data : NULL;
-                if (pdd) {
+                if (pdd && pdd->dev) {
                         to_gpd_data(pdd)->td.constraint_changed = true;
                         genpd = dev_to_genpd(dev);
                 } else {
@@ -1266,6 +1266,27 @@ static void pm_genpd_complete(struct device *dev)
 
 #endif /* CONFIG_PM_SLEEP */
 
+static struct generic_pm_domain_data *__pm_genpd_alloc_dev_data(struct device *dev)
+{
+        struct generic_pm_domain_data *gpd_data;
+
+        gpd_data = kzalloc(sizeof(*gpd_data), GFP_KERNEL);
+        if (!gpd_data)
+                return NULL;
+
+        mutex_init(&gpd_data->lock);
+        gpd_data->nb.notifier_call = genpd_dev_pm_qos_notifier;
+        dev_pm_qos_add_notifier(dev, &gpd_data->nb);
+        return gpd_data;
+}
+
+static void __pm_genpd_free_dev_data(struct device *dev,
+                                     struct generic_pm_domain_data *gpd_data)
+{
+        dev_pm_qos_remove_notifier(dev, &gpd_data->nb);
+        kfree(gpd_data);
+}
+
 /**
  * __pm_genpd_add_device - Add a device to an I/O PM domain.
  * @genpd: PM domain to add the device to.
@@ -1275,7 +1296,7 @@ static void pm_genpd_complete(struct device *dev)
 int __pm_genpd_add_device(struct generic_pm_domain *genpd, struct device *dev,
                           struct gpd_timing_data *td)
 {
-        struct generic_pm_domain_data *gpd_data;
+        struct generic_pm_domain_data *gpd_data_new, *gpd_data = NULL;
         struct pm_domain_data *pdd;
         int ret = 0;
 
@@ -1284,14 +1305,10 @@ int __pm_genpd_add_device(struct generic_pm_domain *genpd, struct device *dev,
         if (IS_ERR_OR_NULL(genpd) || IS_ERR_OR_NULL(dev))
                 return -EINVAL;
 
-        gpd_data = kzalloc(sizeof(*gpd_data), GFP_KERNEL);
-        if (!gpd_data)
+        gpd_data_new = __pm_genpd_alloc_dev_data(dev);
+        if (!gpd_data_new)
                 return -ENOMEM;
 
-        mutex_init(&gpd_data->lock);
-        gpd_data->nb.notifier_call = genpd_dev_pm_qos_notifier;
-        dev_pm_qos_add_notifier(dev, &gpd_data->nb);
-
         genpd_acquire_lock(genpd);
 
         if (genpd->prepared_count > 0) {
@@ -1305,35 +1322,42 @@ int __pm_genpd_add_device(struct generic_pm_domain *genpd, struct device *dev,
                         goto out;
                 }
 
+        ret = dev_pm_get_subsys_data(dev);
+        if (ret)
+                goto out;
+
         genpd->device_count++;
         genpd->max_off_time_changed = true;
 
-        dev_pm_get_subsys_data(dev);
-
-        mutex_lock(&gpd_data->lock);
         spin_lock_irq(&dev->power.lock);
+
         dev->pm_domain = &genpd->domain;
-        dev->power.subsys_data->domain_data = &gpd_data->base;
-        gpd_data->base.dev = dev;
-        list_add_tail(&gpd_data->base.list_node, &genpd->dev_list);
-        gpd_data->need_restore = genpd->status == GPD_STATE_POWER_OFF;
+        if (dev->power.subsys_data->domain_data) {
+                gpd_data = to_gpd_data(dev->power.subsys_data->domain_data);
+        } else {
+                gpd_data = gpd_data_new;
+                dev->power.subsys_data->domain_data = &gpd_data->base;
+        }
+        gpd_data->refcount++;
         if (td)
                 gpd_data->td = *td;
 
+        spin_unlock_irq(&dev->power.lock);
+
+        mutex_lock(&gpd_data->lock);
+        gpd_data->base.dev = dev;
+        list_add_tail(&gpd_data->base.list_node, &genpd->dev_list);
+        gpd_data->need_restore = genpd->status == GPD_STATE_POWER_OFF;
         gpd_data->td.constraint_changed = true;
         gpd_data->td.effective_constraint_ns = -1;
-        spin_unlock_irq(&dev->power.lock);
         mutex_unlock(&gpd_data->lock);
 
-        genpd_release_lock(genpd);
-
-        return 0;
-
  out:
         genpd_release_lock(genpd);
 
-        dev_pm_qos_remove_notifier(dev, &gpd_data->nb);
-        kfree(gpd_data);
+        if (gpd_data != gpd_data_new)
+                __pm_genpd_free_dev_data(dev, gpd_data_new);
+
         return ret;
 }
 
@@ -1379,6 +1403,7 @@ int pm_genpd_remove_device(struct generic_pm_domain *genpd,
 {
         struct generic_pm_domain_data *gpd_data;
         struct pm_domain_data *pdd;
+        bool remove = false;
         int ret = 0;
 
         dev_dbg(dev, "%s()\n", __func__);
@@ -1399,22 +1424,28 @@ int pm_genpd_remove_device(struct generic_pm_domain *genpd,
         genpd->max_off_time_changed = true;
 
         spin_lock_irq(&dev->power.lock);
+
         dev->pm_domain = NULL;
         pdd = dev->power.subsys_data->domain_data;
         list_del_init(&pdd->list_node);
-        dev->power.subsys_data->domain_data = NULL;
+        gpd_data = to_gpd_data(pdd);
+        if (--gpd_data->refcount == 0) {
+                dev->power.subsys_data->domain_data = NULL;
+                remove = true;
+        }
+
         spin_unlock_irq(&dev->power.lock);
 
-        gpd_data = to_gpd_data(pdd);
         mutex_lock(&gpd_data->lock);
         pdd->dev = NULL;
         mutex_unlock(&gpd_data->lock);
 
         genpd_release_lock(genpd);
 
-        dev_pm_qos_remove_notifier(dev, &gpd_data->nb);
-        kfree(gpd_data);
         dev_pm_put_subsys_data(dev);
+        if (remove)
+                __pm_genpd_free_dev_data(dev, gpd_data);
+
         return 0;
 
  out:
diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
index 2febe31d2675..a7d6172922d4 100644
--- a/include/linux/pm_domain.h
+++ b/include/linux/pm_domain.h
@@ -112,6 +112,7 @@ struct generic_pm_domain_data {
         struct gpd_timing_data td;
         struct notifier_block nb;
         struct mutex lock;
+        unsigned int refcount;
         bool need_restore;
         bool always_on;
 };