PM / Domains: Allow generic PM domains to have multiple masters

Currently, for a given generic PM domain there may be only one parent
domain (i.e. a PM domain it depends on).  However, there is at least
one real-life case in which there should be two parents (masters) for
one PM domain (the A3RV domain on SH7372 turns out to depend on the
A4LC domain and it depends on the A4R domain and the same time). For
this reason, allow a PM domain to have multiple parents (masters) by
introducing objects representing links between PM domains.

The (logical) links between PM domains represent relationships in
which one domain is a master (i.e. it is depended on) and another
domain is a slave (i.e. it depends on the master) with the rule that
the slave cannot be powered on if the master is not powered on and
the master cannot be powered off if the slave is not powered off.
Each struct generic_pm_domain object representing a PM domain has
two lists of links, a list of links in which it is a master and
a list of links in which it is a slave.  The first of these lists
replaces the list of subdomains and the second one is used in place
of the parent pointer.

Each link is represented by struct gpd_link object containing
pointers to the master and the slave and two struct list_head
members allowing it to hook into two lists (the master's list
of "master" links and the slave's list of "slave" links).  This
allows the code to get to the link from each side (either from
the master or from the slave) and follow it in each direction.

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

1 files changed, 9 insertions, 3 deletions

diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
index 97e3f8eb4978..5f5154d79253 100644
--- a/include/linux/pm_domain.h
+++ b/include/linux/pm_domain.h
@@ -26,9 +26,8 @@ struct dev_power_governor {
 struct generic_pm_domain {
 	struct dev_pm_domain domain;	/* PM domain operations */
 	struct list_head gpd_list_node;	/* Node in the global PM domains list */
-	struct list_head sd_node;	/* Node in the parent's subdomain list */
-	struct generic_pm_domain *parent;	/* Parent PM domain */
-	struct list_head sd_list;	/* List of dubdomains */
+	struct list_head master_links;	/* Links with PM domain as a master */
+	struct list_head slave_links;	/* Links with PM domain as a slave */
 	struct list_head dev_list;	/* List of devices */
 	struct mutex lock;
 	struct dev_power_governor *gov;
@@ -55,6 +54,13 @@ static inline struct generic_pm_domain *pd_to_genpd(struct dev_pm_domain *pd)
 	return container_of(pd, struct generic_pm_domain, domain);
 }
 
+struct gpd_link {
+	struct generic_pm_domain *master;
+	struct list_head master_node;
+	struct generic_pm_domain *slave;
+	struct list_head slave_node;
+};
+
 struct dev_list_entry {
 	struct list_head node;
 	struct device *dev;