[PATCH v5 22/23] PM: EM: Add em_dev_compute_costs() as API for device drivers

Lukasz Luba
2023-11-29T11:11:12Z

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@arm.com>
---
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 9c47388482a0..836622b1a0a1 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
@@ -355,6 +357,12 @@ 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 234823c0e59d..fadfdefbe5f0 100644
--- a/kernel/power/energy_model.c
+++ b/kernel/power/energy_model.c
@@ -286,6 +286,24 @@ 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