sched: simplify CPU frequency estimation and cycle counter API

Most of CPUs increase cycle counter by one every cycle which makes
frequency = cycles / time_delta is correct.  Therefore it's reasonable
to get rid of current cpu_cycle_max_scale_factor and ask cycle counter
read callback function to return scaled counter value when it's needed
in such a case that cycle counter doesn't increase every cycle.

Thus multiply NSEC_PER_SEC / HZ_PER_KHZ to CPU cycle counter delta
as we calculate frequency in khz and remove cpu_cycle_max_scale_factor.
This allows us to simplify frequency estimation and cycle counter API.

Change-Id: Ie7a628d4bc77c9b6c769f6099ce8d75740262a14
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>

2 files changed, 4 insertions, 40 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index ac5f67da19b9..0b55bbbd7431 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1403,7 +1403,6 @@ static struct sched_cluster init_cluster = {
 	.max_mitigated_freq	=	UINT_MAX,
 	.min_freq		=	1,
 	.max_possible_freq	=	1,
-	.cpu_cycle_max_scale_factor	= 1,
 	.dstate			=	0,
 	.dstate_wakeup_energy	=	0,
 	.dstate_wakeup_latency	=	0,
@@ -1553,7 +1552,6 @@ static struct sched_cluster *alloc_new_cluster(const struct cpumask *cpus)
 	cluster->max_mitigated_freq	=	UINT_MAX;
 	cluster->min_freq		=	1;
 	cluster->max_possible_freq	=	1;
-	cluster->cpu_cycle_max_scale_factor =	1;
 	cluster->dstate			=	0;
 	cluster->dstate_wakeup_energy	=	0;
 	cluster->dstate_wakeup_latency	=	0;
@@ -1620,38 +1618,15 @@ static void init_clusters(void)
 	INIT_LIST_HEAD(&cluster_head);
 }
 
-static inline void
-__update_cpu_cycle_max_possible_freq(struct sched_cluster *cluster)
-{
-	int cpu = cluster_first_cpu(cluster);
-
-	cluster->cpu_cycle_max_scale_factor =
-	    div64_u64(cluster->max_possible_freq * NSEC_PER_USEC,
-		      cpu_cycle_counter_cb.get_cpu_cycles_max_per_us(cpu));
-}
-
-static inline void
-update_cpu_cycle_max_possible_freq(struct sched_cluster *cluster)
-{
-	if (!use_cycle_counter)
-		return;
-
-	__update_cpu_cycle_max_possible_freq(cluster);
-}
-
 int register_cpu_cycle_counter_cb(struct cpu_cycle_counter_cb *cb)
 {
-	struct sched_cluster *cluster = NULL;
-
 	mutex_lock(&cluster_lock);
-	if (!cb->get_cpu_cycle_counter || !cb->get_cpu_cycles_max_per_us) {
+	if (!cb->get_cpu_cycle_counter) {
 		mutex_unlock(&cluster_lock);
 		return -EINVAL;
 	}
 
 	cpu_cycle_counter_cb = *cb;
-	for_each_sched_cluster(cluster)
-		__update_cpu_cycle_max_possible_freq(cluster);
 	use_cycle_counter = true;
 	mutex_unlock(&cluster_lock);
 
@@ -1931,8 +1906,7 @@ static inline u64 scale_exec_time(u64 delta, struct rq *rq,
 	int cpu = cpu_of(rq);
 	int sf;
 
-	delta = DIV64_U64_ROUNDUP(delta * cc->cycles *
-				  cpu_cycle_max_scale_factor(cpu),
+	delta = DIV64_U64_ROUNDUP(delta * cc->cycles,
 				  max_possible_freq * cc->time);
 	sf = DIV_ROUND_UP(cpu_efficiency(cpu) * 1024, max_possible_efficiency);
 
@@ -2613,6 +2587,7 @@ get_task_cpu_cycles(struct task_struct *p, struct rq *rq, int event,
 		cc.cycles = cur_cycles + (U64_MAX - p->cpu_cycles);
 	else
 		cc.cycles = cur_cycles - p->cpu_cycles;
+	cc.cycles = cc.cycles * NSEC_PER_MSEC;
 	cc.time = wallclock - p->ravg.mark_start;
 	BUG_ON((s64)cc.time < 0);
 
@@ -3688,7 +3663,6 @@ static int cpufreq_notifier_policy(struct notifier_block *nb,
 
 			sort_clusters();
 			update_all_clusters_stats();
-			update_cpu_cycle_max_possible_freq(cluster);
 			mutex_unlock(&cluster_lock);
 			continue;
 		}
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 96f5c187dfcd..a66d8a12051c 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -389,11 +389,6 @@ struct sched_cluster {
 	 */
 	unsigned int cur_freq, max_freq, max_mitigated_freq, min_freq;
 	unsigned int max_possible_freq;
-	/*
-	 * cpu_cycle_max_scale_factor represents number of cycles per NSEC at
-	 * CPU's fmax.
-	 */
-	u32 cpu_cycle_max_scale_factor;
 	bool freq_init_done;
 	int dstate, dstate_wakeup_latency, dstate_wakeup_energy;
 	unsigned int static_cluster_pwr_cost;
@@ -1137,14 +1132,9 @@ static inline int cpu_max_power_cost(int cpu)
 	return cpu_rq(cpu)->cluster->max_power_cost;
 }
 
-static inline int cpu_cycle_max_scale_factor(int cpu)
-{
-	return cpu_rq(cpu)->cluster->cpu_cycle_max_scale_factor;
-}
-
 static inline u32 cpu_cycles_to_freq(int cpu, u64 cycles, u32 period)
 {
-	return div64_u64(cycles * cpu_cycle_max_scale_factor(cpu), period);
+	return div64_u64(cycles, period);
 }
 
 static inline bool hmp_capable(void)