PM / Domains: Add "wait for parent" status for generic PM domains

The next patch will make it possible for a generic PM domain to have
multiple parents (i.e. multiple PM domains it depends on).  To
prepare for that change it is necessary to change pm_genpd_poweron()
so that it doesn't jump to the start label after running itself
recursively for the parent domain.  For this purpose, introduce a new
PM domain status value GPD_STATE_WAIT_PARENT that will be set by
pm_genpd_poweron() before calling itself recursively for the parent
domain and modify the code in drivers/base/power/domain.c so that
the GPD_STATE_WAIT_PARENT status is guaranteed to be preserved during
the execution of pm_genpd_poweron() for the parent.

This change also causes pm_genpd_add_subdomain() and
pm_genpd_remove_subdomain() to wait for started pm_genpd_poweron() to
complete and allows pm_genpd_runtime_resume() to avoid dropping the
lock after powering on the PM domain.

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

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index c550f93ac7373379bd8c11e3ec256b5b4ea9d332..c81dff3bd03cdbfefd73e3dd7272e6f846378c2e 100644 (file)
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -81,45 +81,59 @@ static void genpd_set_active(struct generic_pm_domain *genpd)
 }
 
 /**
- * pm_genpd_poweron - Restore power to a given PM domain and its parents.
+ * __pm_genpd_poweron - Restore power to a given PM domain and its parents.
  * @genpd: PM domain to power up.
  *
  * Restore power to @genpd and all of its parents so that it is possible to
  * resume a device belonging to it.
  */
-int pm_genpd_poweron(struct generic_pm_domain *genpd)
+int __pm_genpd_poweron(struct generic_pm_domain *genpd)
+       __releases(&genpd->lock) __acquires(&genpd->lock)
 {
-       struct generic_pm_domain *parent;
+       DEFINE_WAIT(wait);
        int ret = 0;
 
-       mutex_lock(&genpd->lock);
+       /* If the domain's parent is being waited for, we have to wait too. */
+       for (;;) {
+               prepare_to_wait(&genpd->status_wait_queue, &wait,
+                               TASK_UNINTERRUPTIBLE);
+               if (genpd->status != GPD_STATE_WAIT_PARENT)
+                       break;
+               mutex_unlock(&genpd->lock);
 
-       parent = genpd->parent;
+               schedule();
+
+               mutex_lock(&genpd->lock);
+       }
+       finish_wait(&genpd->status_wait_queue, &wait);
 
- start:
        if (genpd->status == GPD_STATE_ACTIVE
            || (genpd->prepared_count > 0 && genpd->suspend_power_off))
-               goto out;
+               return 0;
 
        if (genpd->status != GPD_STATE_POWER_OFF) {
                genpd_set_active(genpd);
-               goto out;
+               return 0;
        }
 
-       if (parent) {
-               genpd_sd_counter_inc(parent);
+       if (genpd->parent) {
+               genpd_sd_counter_inc(genpd->parent);
+               genpd->status = GPD_STATE_WAIT_PARENT;
 
                mutex_unlock(&genpd->lock);
 
-               ret = pm_genpd_poweron(parent);
+               ret = pm_genpd_poweron(genpd->parent);
 
                mutex_lock(&genpd->lock);
 
+               /*
+                * The "wait for parent" status is guaranteed not to change
+                * while the parent is powering on.
+                */
+               genpd->status = GPD_STATE_POWER_OFF;
+               wake_up_all(&genpd->status_wait_queue);
                if (ret)
                        goto err;
-
-               parent = NULL;
-               goto start;
        }
 
        if (genpd->power_on) {
@@ -130,16 +144,27 @@ int pm_genpd_poweron(struct generic_pm_domain *genpd)
 
        genpd_set_active(genpd);
 
- out:
-       mutex_unlock(&genpd->lock);
-
-       return ret;
+       return 0;
 
  err:
        if (genpd->parent)
                genpd_sd_counter_dec(genpd->parent);
 
-       goto out;
+       return ret;
+}
+
+/**
+ * pm_genpd_poweron - Restore power to a given PM domain and its parents.
+ * @genpd: PM domain to power up.
+ */
+int pm_genpd_poweron(struct generic_pm_domain *genpd)
+{
+       int ret;
+
+       mutex_lock(&genpd->lock);
+       ret = __pm_genpd_poweron(genpd);
+       mutex_unlock(&genpd->lock);
+       return ret;
 }
 
 #endif /* CONFIG_PM */
@@ -225,7 +250,8 @@ static void __pm_genpd_restore_device(struct dev_list_entry *dle,
  */
 static bool genpd_abort_poweroff(struct generic_pm_domain *genpd)
 {
-       return genpd->status == GPD_STATE_ACTIVE || genpd->resume_count > 0;
+       return genpd->status == GPD_STATE_WAIT_PARENT
+               || genpd->status == GPD_STATE_ACTIVE || genpd->resume_count > 0;
 }
 
 /**
@@ -261,11 +287,13 @@ static int pm_genpd_poweroff(struct generic_pm_domain *genpd)
        /*
         * Do not try to power off the domain in the following situations:
         * (1) The domain is already in the "power off" state.
-        * (2) System suspend is in progress.
+        * (2) The domain is waiting for its parent to power up.
         * (3) One of the domain's devices is being resumed right now.
+        * (4) System suspend is in progress.
         */
-       if (genpd->status == GPD_STATE_POWER_OFF || genpd->prepared_count > 0
-           || genpd->resume_count > 0)
+       if (genpd->status == GPD_STATE_POWER_OFF
+           || genpd->status == GPD_STATE_WAIT_PARENT
+           || genpd->resume_count > 0 || genpd->prepared_count > 0)
                return 0;
 
        if (atomic_read(&genpd->sd_count) > 0)
@@ -299,14 +327,15 @@ static int pm_genpd_poweroff(struct generic_pm_domain *genpd)
        list_for_each_entry_reverse(dle, &genpd->dev_list, node) {
                ret = atomic_read(&genpd->sd_count) == 0 ?
                        __pm_genpd_save_device(dle, genpd) : -EBUSY;
+
+               if (genpd_abort_poweroff(genpd))
+                       goto out;
+
                if (ret) {
                        genpd_set_active(genpd);
                        goto out;
                }
 
-               if (genpd_abort_poweroff(genpd))
-                       goto out;
-
                if (genpd->status == GPD_STATE_REPEAT) {
                        genpd->poweroff_task = NULL;
                        goto start;
@@ -432,11 +461,12 @@ static int pm_genpd_runtime_resume(struct device *dev)
        if (IS_ERR(genpd))
                return -EINVAL;
 
-       ret = pm_genpd_poweron(genpd);
-       if (ret)
-               return ret;
-
        mutex_lock(&genpd->lock);
+       ret = __pm_genpd_poweron(genpd);
+       if (ret) {
+               mutex_unlock(&genpd->lock);
+               return ret;
+       }
        genpd->status = GPD_STATE_BUSY;
        genpd->resume_count++;
        for (;;) {

diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
index 2693ffe1904c506714f6f115083e25bfc563844c..ba8cd390f3b953e6c6bac464afe9000c44e3f8b2 100644 (file)
--- a/include/linux/pm_domain.h
+++ b/include/linux/pm_domain.h
@@ -13,6 +13,7 @@
 
 enum gpd_status {
        GPD_STATE_ACTIVE = 0,   /* PM domain is active */
+       GPD_STATE_WAIT_PARENT,  /* PM domain's parent is being waited for */
        GPD_STATE_BUSY,         /* Something is happening to the PM domain */
        GPD_STATE_REPEAT,       /* Power off in progress, to be repeated */
        GPD_STATE_POWER_OFF,    /* PM domain is off */