@@ -159,6 +159,56 @@ static inline int em_pd_nr_cap_states(struct em_perf_domain *pd)
return pd->nr_cap_states;
}
+#define EM_COST_MARGIN_SCALE 1024U
+
+/**
+ * em_pd_get_higher_freq() - Get the highest frequency that does not exceed the
+ * given cost margin compared to min_freq
+ * @pd : performance domain for which this must be done
+ * @min_freq : minimum frequency to return
+ * @cost_margin : allowed cost margin on the EM_COST_MARGIN_SCALE scale. The
+ * maximum value of the scale maps to the highest cost in that perf domain.
+ *
+ * Return: the chosen frequency, guaranteed to be at least as high as min_freq.
+ */
+static inline unsigned long em_pd_get_higher_freq(struct em_perf_domain *pd,
+ unsigned long min_freq, unsigned long cost_margin)
+{
+ unsigned long max_cost;
+ unsigned long max_allowed_cost = 0;
+ struct em_cap_state *cs;
+ int i;
+
+ if (!pd)
+ return min_freq;
+
+ max_cost = pd->table[pd->nr_cap_states - 1].cost;
+ cost_margin = (cost_margin * max_cost) / EM_COST_MARGIN_SCALE;
+
+ /* Compute the maximum allowed cost */
+ for (i = 0; i < pd->nr_cap_states; i++) {
+ cs = &pd->table[i];
+ if (cs->frequency >= min_freq) {
+ max_allowed_cost = cs->cost + cost_margin;
+ break;
+ }
+ }
+
+ /* Find the highest frequency that will not exceed the cost margin */
+ for (i = pd->nr_cap_states-1; i >= 0; i--) {
+ cs = &pd->table[i];
+ if (cs->cost <= max_allowed_cost)
+ return cs->frequency;
+ }
+
+ /*
+ * min_freq can be higher than the highest available frequency since
+ * map_util_freq() will multiply the minimum frequency by some amount.
+ * This can allow it to be higher than the maximum achievable frequency.
+ */
+ return min_freq;
+}
+
#else
struct em_data_callback {};
#define EM_DATA_CB(_active_power_cb) { }
@@ -181,6 +231,12 @@ static inline int em_pd_nr_cap_states(struct em_perf_domain *pd)
{
return 0;
}
+
+static inline unsigned long em_pd_get_higher_freq(struct em_perf_domain *pd,
+ unsigned long min_freq, unsigned long cost_margin)
+{
+ return min_freq;
+}
#endif
#endif
em_pd_get_higher_freq() returns a frequency greater or equal to the provided one while taking into account a given cost margin. It also skips inefficient OPPs that have a higher cost than another one with a higher frequency (ordering OPPs by cost or efficiency leads to the same result within a given CPU). The efficiency of an OPP is measured as efficiency=capacity/power. OPPs with the same efficiency are assumed to be equivalent, since they will consume as much energy for a given amount of work to do. That may take more or less time depending on the frequency, but will consume the same energy. Signed-off-by: Douglas RAILLARD <douglas.raillard@arm.com> --- include/linux/energy_model.h | 56 ++++++++++++++++++++++++++++++++++++ 1 file changed, 56 insertions(+)