cpufreq: Call transition notifier only once for each policy

Currently, the notifiers are called once for each CPU of the policy->cpus
cpumask. It would be more optimal if the notifier can be called only
once and all the relevant information be provided to it. Out of the 23
drivers that register for the transition notifiers today, only 4 of them
do per-cpu updates and the callback for the rest can be called only once
for the policy without any impact.

This would also avoid multiple function calls to the notifier callbacks
and reduce multiple iterations of notifier core's code (which does
locking as well).

This patch adds pointer to the cpufreq policy to the struct
cpufreq_freqs, so the notifier callback has all the information
available to it with a single call. The five drivers which perform
per-cpu updates are updated to use the cpufreq policy. The freqs->cpu
field is redundant now and is removed.

Acked-by: David S. Miller <davem@davemloft.net> (sparc)
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 15 insertions, 9 deletions

diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index facd4240ca02..c6d37563610a 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -754,15 +754,20 @@ static int cpufreq_callback(struct notifier_block *nb,
 					unsigned long val, void *data)
 {
 	struct cpufreq_freqs *freq = data;
-	int cpu = freq->cpu;
+	struct cpumask *cpus = freq->policy->cpus;
+	int cpu, first = cpumask_first(cpus);
+	unsigned int lpj;
 
 	if (freq->flags & CPUFREQ_CONST_LOOPS)
 		return NOTIFY_OK;
 
-	if (!per_cpu(l_p_j_ref, cpu)) {
-		per_cpu(l_p_j_ref, cpu) =
-			per_cpu(cpu_data, cpu).loops_per_jiffy;
-		per_cpu(l_p_j_ref_freq, cpu) = freq->old;
+	if (!per_cpu(l_p_j_ref, first)) {
+		for_each_cpu(cpu, cpus) {
+			per_cpu(l_p_j_ref, cpu) =
+				per_cpu(cpu_data, cpu).loops_per_jiffy;
+			per_cpu(l_p_j_ref_freq, cpu) = freq->old;
+		}
+
 		if (!global_l_p_j_ref) {
 			global_l_p_j_ref = loops_per_jiffy;
 			global_l_p_j_ref_freq = freq->old;
@@ -774,10 +779,11 @@ static int cpufreq_callback(struct notifier_block *nb,
 		loops_per_jiffy = cpufreq_scale(global_l_p_j_ref,
 						global_l_p_j_ref_freq,
 						freq->new);
-		per_cpu(cpu_data, cpu).loops_per_jiffy =
-			cpufreq_scale(per_cpu(l_p_j_ref, cpu),
-					per_cpu(l_p_j_ref_freq, cpu),
-					freq->new);
+
+		lpj = cpufreq_scale(per_cpu(l_p_j_ref, first),
+				    per_cpu(l_p_j_ref_freq, first), freq->new);
+		for_each_cpu(cpu, cpus)
+			per_cpu(cpu_data, cpu).loops_per_jiffy = lpj;
 	}
 	return NOTIFY_OK;
 }