linux-kernel - [PATCH 2/3] PM: EM: Make em_cpu_energy() able to return bigger values

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Message-Id: <20210625152603.25960-3-lukasz.luba@arm.com>
Date:   Fri, 25 Jun 2021 16:26:02 +0100
From:   Lukasz Luba <lukasz.luba@....com>
To:     linux-kernel@...r.kernel.org
Cc:     Chris.Redpath@....com, lukasz.luba@....com,
        dietmar.eggemann@....com, morten.rasmussen@....com,
        qperret@...gle.com, linux-pm@...r.kernel.org, peterz@...radead.org,
        rjw@...ysocki.net, viresh.kumar@...aro.org,
        vincent.guittot@...aro.org, mingo@...hat.com,
        juri.lelli@...hat.com, rostedt@...dmis.org, segall@...gle.com,
        mgorman@...e.de, bristot@...hat.com, CCj.Yeh@...iatek.com
Subject: [PATCH 2/3] PM: EM: Make em_cpu_energy() able to return bigger values

The Energy Model (EM) em_cpu_energy() is responsible for providing good
estimation regarding CPUs energy. It contains proper data structures which
are then used during calculation. The values stored in there are in
milli-Watts precision (or in abstract scale) smaller that 0xffff, which use
sufficient unsigned long even on 32-bit machines. There are scenarios where
we would like to provide calculated estimations in a better precision and
the values might be 1000 times bigger. This patch makes possible to use
quite big values for also 32-bit machines.

Signed-off-by: Lukasz Luba <lukasz.luba@....com>
---
 include/linux/energy_model.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/linux/energy_model.h b/include/linux/energy_model.h
index 3f221dbf5f95..2016f5a706e0 100644
--- a/include/linux/energy_model.h
+++ b/include/linux/energy_model.h
@@ -101,7 +101,7 @@ void em_dev_unregister_perf_domain(struct device *dev);
  * Return: the sum of the energy consumed by the CPUs of the domain assuming
  * a capacity state satisfying the max utilization of the domain.
  */
-static inline unsigned long em_cpu_energy(struct em_perf_domain *pd,
+static inline u64 em_cpu_energy(struct em_perf_domain *pd,
 				unsigned long max_util, unsigned long sum_util,
 				unsigned long allowed_cpu_cap)
 {
@@ -180,7 +180,7 @@ static inline unsigned long em_cpu_energy(struct em_perf_domain *pd,
 	 *   pd_nrg = ------------------------                       (4)
 	 *                  scale_cpu
 	 */
-	return ps->cost * sum_util / scale_cpu;
+	return div_u64((u64)ps->cost * sum_util, scale_cpu);
 }
 
 /**
@@ -217,7 +217,7 @@ static inline struct em_perf_domain *em_pd_get(struct device *dev)
 {
 	return NULL;
 }
-static inline unsigned long em_cpu_energy(struct em_perf_domain *pd,
+static inline u64 em_cpu_energy(struct em_perf_domain *pd,
 			unsigned long max_util, unsigned long sum_util,
 			unsigned long allowed_cpu_cap)
 {
-- 
2.17.1