ARM: add cpufreq transiton notifier to adjust loops_per_jiffy for smp

If CONFIG_SMP, cpufreq skips loops_per_jiffy update, because different
arch has different per-cpu loops_per_jiffy definition.

Signed-off-by: Richard Zhao <richard.zhao@linaro.org>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>

Notes by Sudeep KarkadaNagesha <Sudeep.KarkadaNagesha@arm.com>:
Even though this patch is accepted by Russell, its not in the mainline
kernel yet. However this can be removed if Will Deacon's "Use architected
timers for delay loop" is accepted.
http://www.spinics.net/lists/arm-kernel/msg180836.html

1 files changed, 54 insertions, 0 deletions

diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index 853f4e94a20..d02413f6cdf 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -25,6 +25,7 @@
 #include <linux/percpu.h>
 #include <linux/clockchips.h>
 #include <linux/completion.h>
+#include <linux/cpufreq.h>
 
 #include <linux/atomic.h>
 #include <asm/cacheflush.h>
@@ -583,3 +584,56 @@ int setup_profiling_timer(unsigned int multiplier)
 {
 	return -EINVAL;
 }
+
+#ifdef CONFIG_CPU_FREQ
+
+static DEFINE_PER_CPU(unsigned long, l_p_j_ref);
+static DEFINE_PER_CPU(unsigned long, l_p_j_ref_freq);
+static unsigned long global_l_p_j_ref;
+static unsigned long global_l_p_j_ref_freq;
+
+static int cpufreq_callback(struct notifier_block *nb,
+					unsigned long val, void *data)
+{
+	struct cpufreq_freqs *freq = data;
+	int cpu = freq->cpu;
+
+	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 (!global_l_p_j_ref) {
+			global_l_p_j_ref = loops_per_jiffy;
+			global_l_p_j_ref_freq = freq->old;
+		}
+	}
+
+	if ((val == CPUFREQ_PRECHANGE  && freq->old < freq->new) ||
+	    (val == CPUFREQ_POSTCHANGE && freq->old > freq->new) ||
+	    (val == CPUFREQ_RESUMECHANGE || val == CPUFREQ_SUSPENDCHANGE)) {
+		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);
+	}
+	return NOTIFY_OK;
+}
+
+static struct notifier_block cpufreq_notifier = {
+	.notifier_call  = cpufreq_callback,
+};
+
+static int __init register_cpufreq_notifier(void)
+{
+	return cpufreq_register_notifier(&cpufreq_notifier,
+						CPUFREQ_TRANSITION_NOTIFIER);
+}
+core_initcall(register_cpufreq_notifier);
+
+#endif