[PATCH v3 2/9] PM / Domains: Enable genpd to support ->get|put() callbacks

[Ulf Hansson]

To provide users control over whether the power should be maintained,
implement the ->get|put() callbacks for genpd's PM domain.

A usage count variable keeps track of the number of users. A positive
value tells genpd to keep supplying power and also to power up if it's
the first user.

Do note, the above applies no matter of CONFIG_PM_RUNTIME. That's
because we allows a PM domain to be initialized in power off state and
thus we need a way to power it up.

Once the usage count reaches zero, genpd tries to power off its PM
domain. Although for !CONFIG_PM_RUNTIME we need to maintain the power
once it's been enabled, since drivers can't use runtime PM to restore
it dynamically.

Signed-off-by: Ulf Hansson <ulf.hansson at linaro.org>
---
 drivers/base/power/domain.c | 26 +++++++++++++++++++++++++-
 include/linux/pm_domain.h   |  1 +
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 40bc2f4..96fe72e 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -451,10 +451,12 @@ static int pm_genpd_poweroff(struct generic_pm_domain *genpd)
 	 * (2) The domain is waiting for its master to power up.
 	 * (3) One of the domain's devices is being resumed right now.
 	 * (4) System suspend is in progress.
+	 * (5) The usage_count > 0, since it tells us to stay powered.
 	 */
 	if (genpd->status == GPD_STATE_POWER_OFF
 	    || genpd->status == GPD_STATE_WAIT_MASTER
-	    || genpd->resume_count > 0 || genpd->prepared_count > 0)
+	    || genpd->resume_count > 0 || genpd->prepared_count > 0
+	    || atomic_read(&genpd->usage_count) > 0)
 		return 0;
 
 	if (atomic_read(&genpd->sd_count) > 0)
@@ -1358,6 +1360,25 @@ EXPORT_SYMBOL_GPL(pm_genpd_syscore_poweron);
 
 #endif /* CONFIG_PM_SLEEP */
 
+static int pm_genpd_get(struct dev_pm_domain *domain)
+{
+	struct generic_pm_domain *genpd = pd_to_genpd(domain);
+
+	atomic_inc(&genpd->usage_count);
+
+	return pm_genpd_poweron(genpd);
+}
+
+static void pm_genpd_put(struct dev_pm_domain *domain)
+{
+	struct generic_pm_domain *genpd = pd_to_genpd(domain);
+
+	if (!atomic_dec_and_test(&genpd->usage_count))
+		return;
+
+	genpd_queue_power_off_work(genpd);
+}
+
 static struct generic_pm_domain_data *__pm_genpd_alloc_dev_data(struct device *dev)
 {
 	struct generic_pm_domain_data *gpd_data;
@@ -1875,10 +1896,13 @@ void pm_genpd_init(struct generic_pm_domain *genpd,
 	genpd->status = is_off ? GPD_STATE_POWER_OFF : GPD_STATE_ACTIVE;
 	init_waitqueue_head(&genpd->status_wait_queue);
 	genpd->poweroff_task = NULL;
+	atomic_set(&genpd->usage_count, 0);
 	genpd->resume_count = 0;
 	genpd->device_count = 0;
 	genpd->max_off_time_ns = -1;
 	genpd->max_off_time_changed = true;
+	genpd->domain.get = pm_genpd_get;
+	genpd->domain.put = pm_genpd_put;
 	genpd->domain.ops.runtime_suspend = pm_genpd_runtime_suspend;
 	genpd->domain.ops.runtime_resume = pm_genpd_runtime_resume;
 	genpd->domain.ops.prepare = pm_genpd_prepare;
diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
index 8e2806f..7b3cba2 100644
--- a/include/linux/pm_domain.h
+++ b/include/linux/pm_domain.h
@@ -58,6 +58,7 @@ struct generic_pm_domain {
 	enum gpd_status status;	/* Current state of the domain */
 	wait_queue_head_t status_wait_queue;
 	struct task_struct *poweroff_task;	/* Powering off task */
+	atomic_t usage_count;		/* Number of users of the domain */
 	unsigned int resume_count;	/* Number of devices being resumed */
 	unsigned int device_count;	/* Number of devices */
 	unsigned int suspended_count;	/* System suspend device counter */
-- 
1.9.1