From a7e049b7651a6ee03b048e78442a513b0a26868e Mon Sep 17 00:00:00 2001
From: Doug Smythies <dsmythies@telus.net>
Date: Sat, 14 Jun 2014 22:30:52 -0700
Subject: [PATCH 2/4] intel_pstate: Include C0 for light loads only.

---
 drivers/cpufreq/intel_pstate.c | 34 ++++++++++++++++++++++++++++++----
 1 file changed, 30 insertions(+), 4 deletions(-)

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index c1178ba..5f38783 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -59,6 +59,10 @@ struct sample {
 	int32_t core_pct_busy;
 	u64 aperf;
 	u64 mperf;
+	u64 tsc;
+	u64 c0_1;
+	u64 c0_2;
+	u64 c0_3;
 	int freq;
 };
 
@@ -99,6 +103,7 @@ struct cpudata {
 
 	u64	prev_aperf;
 	u64	prev_mperf;
+	u64 prev_tsc;
 	struct sample sample;
 };
 
@@ -561,40 +566,61 @@ static void intel_pstate_get_cpu_pstates(struct cpudata *cpu)
 static inline void intel_pstate_calc_busy(struct cpudata *cpu,
 					struct sample *sample)
 {
+
+#define C0_THRESHOLD 4 << FRAC_BITS
+#define C0_SCALE (100 << (FRAC_BITS)) / (C0_THRESHOLD)
+
 	int64_t core_pct;
-	int32_t rem;
+	int64_t c0_pct, c0_scaled;
 
 	core_pct = int_tofp(sample->aperf) * int_tofp(100);
-	core_pct = div_u64_rem(core_pct, int_tofp(sample->mperf), &rem);
+	core_pct = div_u64(core_pct, int_tofp(sample->mperf));
 
-	if ((rem << 1) >= int_tofp(sample->mperf))
-		core_pct += 1;
+	c0_pct = int_tofp(sample->mperf) * int_tofp(100);
+	c0_pct = div_u64(c0_pct, int_tofp(sample->tsc));
 
 	sample->freq = fp_toint(
 		mul_fp(int_tofp(cpu->pstate.max_pstate * 1000), core_pct));
 
+	if(c0_pct < C0_THRESHOLD && sample->c0_1 < C0_THRESHOLD && sample->c0_2 < C0_THRESHOLD && sample->c0_3 < C0_THRESHOLD)
+	{
+		c0_scaled = c0_pct * C0_SCALE;
+		core_pct = core_pct - int_tofp(limits.min_perf_pct);
+		core_pct = core_pct * c0_scaled;
+		core_pct = div_u64(core_pct, int_tofp(100));
+		core_pct = core_pct + int_tofp(limits.min_perf_pct);
+	}
 	sample->core_pct_busy = (int32_t)core_pct;
+	sample->c0_3 = sample->c0_2;
+	sample->c0_2 = sample->c0_1;
+	sample->c0_1 = c0_pct;
 }
 
 static inline void intel_pstate_sample(struct cpudata *cpu)
 {
 	u64 aperf, mperf;
+	unsigned long long tsc;
 
 	rdmsrl(MSR_IA32_APERF, aperf);
 	rdmsrl(MSR_IA32_MPERF, mperf);
+	tsc = native_read_tsc();
 
 	aperf = aperf >> FRAC_BITS;
 	mperf = mperf >> FRAC_BITS;
+	tsc = tsc >> FRAC_BITS;
 
 	cpu->sample.aperf = aperf;
 	cpu->sample.mperf = mperf;
+	cpu->sample.tsc = (u64) tsc;
 	cpu->sample.aperf -= cpu->prev_aperf;
 	cpu->sample.mperf -= cpu->prev_mperf;
+	cpu->sample.tsc -= cpu->prev_tsc;
 
 	intel_pstate_calc_busy(cpu, &cpu->sample);
 
 	cpu->prev_aperf = aperf;
 	cpu->prev_mperf = mperf;
+	cpu->prev_tsc = (u64) tsc;
 }
 
 static inline void intel_pstate_set_sample_time(struct cpudata *cpu)
-- 
1.9.1