[PATCH v6 22/23] PM: EM: Add em_dev_compute_costs() as API for device drivers

[Lukasz Luba]

The device drivers can modify EM at runtime by providing a new EM table.
The EM is used by the EAS and the em_perf_state::cost stores
pre-calculated value to avoid overhead. This patch provides the API for
device drivers to calculate the cost values properly (and not duplicate
the same code).

Signed-off-by: Lukasz Luba <lukasz.luba@xxxxxxx>
---
 include/linux/energy_model.h |  8 ++++++++
 kernel/power/energy_model.c  | 18 ++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/include/linux/energy_model.h b/include/linux/energy_model.h
index dd8a69bdf0d0..f50f3c6ab2e5 100644
--- a/include/linux/energy_model.h
+++ b/include/linux/energy_model.h
@@ -170,6 +170,8 @@ int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states,
 void em_dev_unregister_perf_domain(struct device *dev);
 struct em_perf_table __rcu *em_allocate_table(struct em_perf_domain *pd);
 void em_free_table(struct em_perf_table __rcu *table);
+int em_dev_compute_costs(struct device *dev, struct em_perf_state *table,
+			 int nr_states);
 
 /**
  * em_pd_get_efficient_state() - Get an efficient performance state from the EM
@@ -375,6 +377,12 @@ static inline struct em_perf_state *em_get_table(struct em_perf_domain *pd)
 	return NULL;
 }
 static inline void em_put_table(void) {}
+static inline
+int em_dev_compute_costs(struct device *dev, struct em_perf_state *table,
+			 int nr_states)
+{
+	return -EINVAL;
+}
 #endif
 
 #endif
diff --git a/kernel/power/energy_model.c b/kernel/power/energy_model.c
index 79877d8975d5..7f9337f4ae30 100644
--- a/kernel/power/energy_model.c
+++ b/kernel/power/energy_model.c
@@ -285,6 +285,24 @@ static int em_compute_costs(struct device *dev, struct em_perf_state *table,
 	return 0;
 }
 
+/**
+ * em_dev_compute_costs() - Calculate cost values for new runtime EM table
+ * @dev		: Device for which the EM table is to be updated
+ * @table	: The new EM table that is going to get the costs calculated
+ *
+ * Calculate the em_perf_state::cost values for new runtime EM table. The
+ * values are used for EAS during task placement. It also calculates and sets
+ * the efficiency flag for each performance state. When the function finish
+ * successfully the EM table is ready to be updated and used by EAS.
+ *
+ * Return 0 on success or a proper error in case of failure.
+ */
+int em_dev_compute_costs(struct device *dev, struct em_perf_state *table,
+			 int nr_states)
+{
+	return em_compute_costs(dev, table, NULL, nr_states, 0);
+}
+
 /**
  * em_dev_update_perf_domain() - Update runtime EM table for a device
  * @dev		: Device for which the EM is to be updated
-- 
2.25.1