[RFC PATCH v2 1/2] PM: domains: Skip disabling unused domains if provider has sync_state

[Abel Vesa]

Currently, there are cases when a domain needs to remain enabled until
the consumer driver probes. Sometimes such consumer drivers may be built
as modules. Since the genpd_power_off_unused is called too early for
such consumer driver modules to get a chance to probe, the domain, since
it is unused, will get disabled. On the other hand, the best time for
an unused domain to be disabled is on the provider's sync_state
callback. So, if the provider has registered a sync_state callback,
assume the unused domains for that provider will be disabled on its
sync_state callback. Also provide a generic sync_state callback which
disables all the domains unused for the provider that registers it.

Signed-off-by: Abel Vesa <abel.vesa@xxxxxxxxxx>
---

This approach has been applied for unused clocks as well.
With this patch merged in, all the providers that have sync_state
callback registered will leave the domains enabled unless the provider's
sync_state callback explicitly disables them. So those providers will
need to add the disabling part to their sync_state callback. On the
other hand, the platforms that have cases where domains need to remain
enabled (even if unused) until the consumer driver probes, will be able,
with this patch in, to run without the pd_ignore_unused kernel argument,
which seems to be the case for most Qualcomm platforms, at this moment.

The v1 is here:
https://lore.kernel.org/all/20230126234013.3638425-1-abel.vesa@xxxxxxxxxx/

Changes since v1:
 * added a generic sync state callback to be registered by providers in
   order to disable the unused domains on their sync state. Also
   mentioned this in the commit message.

 drivers/base/power/domain.c | 17 ++++++++++++++++-
 include/linux/pm_domain.h   |  3 +++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 84662d338188..c2a5f77c01f3 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -1099,7 +1099,8 @@ static int __init genpd_power_off_unused(void)
 	mutex_lock(&gpd_list_lock);
 
 	list_for_each_entry(genpd, &gpd_list, gpd_list_node)
-		genpd_queue_power_off_work(genpd);
+		if (!dev_has_sync_state(genpd->provider->dev))
+			genpd_queue_power_off_work(genpd);
 
 	mutex_unlock(&gpd_list_lock);
 
@@ -1107,6 +1108,20 @@ static int __init genpd_power_off_unused(void)
 }
 late_initcall(genpd_power_off_unused);
 
+void genpd_power_off_unused_sync_state(struct device *dev)
+{
+	struct generic_pm_domain *genpd;
+
+	mutex_lock(&gpd_list_lock);
+
+	list_for_each_entry(genpd, &gpd_list, gpd_list_node)
+		if (genpd->provider->dev == dev)
+			genpd_queue_power_off_work(genpd);
+
+	mutex_unlock(&gpd_list_lock);
+}
+EXPORT_SYMBOL_GPL(genpd_power_off_unused_sync_state);
+
 #ifdef CONFIG_PM_SLEEP
 
 /**
diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
index f776fb93eaa0..1fd5aa500c81 100644
--- a/include/linux/pm_domain.h
+++ b/include/linux/pm_domain.h
@@ -351,6 +351,7 @@ struct device *genpd_dev_pm_attach_by_id(struct device *dev,
 					 unsigned int index);
 struct device *genpd_dev_pm_attach_by_name(struct device *dev,
 					   const char *name);
+void genpd_power_off_unused_sync_state(struct device *dev);
 #else /* !CONFIG_PM_GENERIC_DOMAINS_OF */
 static inline int of_genpd_add_provider_simple(struct device_node *np,
 					struct generic_pm_domain *genpd)
@@ -419,6 +420,8 @@ struct generic_pm_domain *of_genpd_remove_last(struct device_node *np)
 {
 	return ERR_PTR(-EOPNOTSUPP);
 }
+
+static inline genpd_power_off_unused_sync_state(struct device *dev) {}
 #endif /* CONFIG_PM_GENERIC_DOMAINS_OF */
 
 #ifdef CONFIG_PM
-- 
2.34.1