[PATCH V3 6/6] PM / Domains: Propagate performance state updates

From: Viresh Kumar
Date: Wed Dec 12 2018 - 05:58:10 EST

This commit updates genpd core to start propagating performance state
updates to master domains that have their set_performance_state()
callback set.

Currently a genpd only handles the performance state requirements from
the devices under its control. This commit extends that to also handle
the performance state requirement(s) put on the master genpd by its
sub-domains. There is a separate value required for each master that
the genpd has and so a new field is added to the struct gpd_link
(link->performance_state), which represents the link between a genpd and
its master. The struct gpd_link also got another field
prev_performance_state, which is used by genpd core as a temporary
variable during transitions.

Tested-by: Rajendra Nayak <rnayak@xxxxxxxxxxxxxx>
Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
---
drivers/base/power/domain.c | 105 ++++++++++++++++++++++++++++++------
include/linux/pm_domain.h | 4 ++
2 files changed, 94 insertions(+), 15 deletions(-)

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 32ecbefbd191..5e0479b2e976 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -239,24 +239,90 @@ static void genpd_update_accounting(struct generic_pm_domain *genpd)
static inline void genpd_update_accounting(struct generic_pm_domain *genpd) {}
#endif

+static int _genpd_reeval_performance_state(struct generic_pm_domain *genpd,
+ unsigned int state, int depth);
+
static int _genpd_set_performance_state(struct generic_pm_domain *genpd,
- unsigned int state)
+ unsigned int state, int depth)
{
+ struct generic_pm_domain *master;
+ struct gpd_link *link;
+ unsigned int master_state;
int ret;

+ /* Propagate to masters of genpd */
+ list_for_each_entry(link, &genpd->slave_links, slave_node) {
+ master = link->master;
+
+ if (!master->set_performance_state)
+ continue;
+
+ if (unlikely(!state)) {
+ master_state = 0;
+ } else {
+ /* Find master's performance state */
+ master_state = dev_pm_opp_xlate_performance_state(genpd->opp_table,
+ master->opp_table, state);
+ if (unlikely(!master_state)) {
+ ret = -EINVAL;
+ goto err;
+ }
+ }
+
+ genpd_lock_nested(master, depth + 1);
+
+ link->prev_performance_state = link->performance_state;
+ link->performance_state = master_state;
+ ret = _genpd_reeval_performance_state(master, master_state,
+ depth + 1);
+ if (ret)
+ link->performance_state = link->prev_performance_state;
+
+ genpd_unlock(master);
+
+ if (ret)
+ goto err;
+ }
+
ret = genpd->set_performance_state(genpd, state);
if (ret)
- return ret;
+ goto err;

genpd->performance_state = state;
return 0;
+
+err:
+ /* Encountered an error, lets rollback */
+ list_for_each_entry_continue_reverse(link, &genpd->slave_links,
+ slave_node) {
+ master = link->master;
+
+ if (!master->set_performance_state)
+ continue;
+
+ genpd_lock_nested(master, depth + 1);
+
+ master_state = link->prev_performance_state;
+ link->performance_state = master_state;
+
+ if (_genpd_reeval_performance_state(master, master_state,
+ depth + 1)) {
+ pr_err("%s: Failed to roll back to %d performance state\n",
+ master->name, master_state);
+ }
+
+ genpd_unlock(master);
+ }
+
+ return ret;
}

static int _genpd_reeval_performance_state(struct generic_pm_domain *genpd,
- unsigned int state)
+ unsigned int state, int depth)
{
struct generic_pm_domain_data *pd_data;
struct pm_domain_data *pdd;
+ struct gpd_link *link;

/* New requested state is same as Max requested state */
if (state == genpd->performance_state)
@@ -274,21 +340,30 @@ static int _genpd_reeval_performance_state(struct generic_pm_domain *genpd,
state = pd_data->performance_state;
}

- if (state == genpd->performance_state)
- return 0;
-
/*
- * We aren't propagating performance state changes of a subdomain to its
- * masters as we don't have hardware that needs it. Over that, the
- * performance states of subdomain and its masters may not have
- * one-to-one mapping and would require additional information. We can
- * get back to this once we have hardware that needs it. For that
- * reason, we don't have to consider performance state of the subdomains
- * of genpd here.
+ * Traverse all sub-domains within the domain. This can be
+ * done without any additional locking as the link->performance_state
+ * field is protected by the master genpd->lock, which is already taken.
+ *
+ * Also note that link->performance_state (subdomain's performance state
+ * requirement to master domain) is different from
+ * link->slave->performance_state (current performance state requirement
+ * of the devices/sub-domains of the subdomain) and so can have a
+ * different value.
+ *
+ * Note that we also take vote from powered-off sub-domains into account
+ * as the same is done for devices right now.
*/
+ list_for_each_entry(link, &genpd->master_links, master_node) {
+ if (link->performance_state > state)
+ state = link->performance_state;
+ }
+
+ if (state == genpd->performance_state)
+ return 0;

update_state:
- return _genpd_set_performance_state(genpd, state);
+ return _genpd_set_performance_state(genpd, state, depth);
}

/**
@@ -332,7 +407,7 @@ int dev_pm_genpd_set_performance_state(struct device *dev, unsigned int state)
prev = gpd_data->performance_state;
gpd_data->performance_state = state;

- ret = _genpd_reeval_performance_state(genpd, state);
+ ret = _genpd_reeval_performance_state(genpd, state, 0);
if (ret)
gpd_data->performance_state = prev;

diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
index 9ad101362aef..dd364abb649a 100644
--- a/include/linux/pm_domain.h
+++ b/include/linux/pm_domain.h
@@ -136,6 +136,10 @@ struct gpd_link {
struct list_head master_node;
struct generic_pm_domain *slave;
struct list_head slave_node;
+
+ /* Sub-domain's per-master domain performance state */
+ unsigned int performance_state;
+ unsigned int prev_performance_state;
};

struct gpd_timing_data {
--
2.19.1.568.g152ad8e3369a