[PATCH 3.12 32/32] intel_pstate: Take core C0 time into account for core busy calculation

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

3.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dirk Brandewie <dirk.j.brandewie@intel.com>

commit fcb6a15c2e7e76d493e6f91ea889ab40e1c643a4 upstream.

Take non-idle time into account when calculating core busy time.
This ensures that intel_pstate will notice a decrease in load.

References: https://bugzilla.kernel.org/show_bug.cgi?id=66581
Cc: 3.10+ <stable@vger.kernel.org> # 3.10+
Signed-off-by: Dirk Brandewie <dirk.j.brandewie@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/cpufreq/intel_pstate.c |   16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -51,6 +51,7 @@ struct sample {
 	int32_t core_pct_busy;
 	u64 aperf;
 	u64 mperf;
+	unsigned long long tsc;
 	int freq;
 };
 
@@ -86,6 +87,7 @@ struct cpudata {
 
 	u64	prev_aperf;
 	u64	prev_mperf;
+	unsigned long long prev_tsc;
 	int	sample_ptr;
 	struct sample samples[SAMPLE_COUNT];
 };
@@ -436,11 +438,17 @@ static inline void intel_pstate_calc_bus
 					struct sample *sample)
 {
 	u64 core_pct;
-	core_pct = div64_u64(int_tofp(sample->aperf * 100),
-			     sample->mperf);
-	sample->freq = fp_toint(cpu->pstate.max_pstate * core_pct * 1000);
+	u64 c0_pct;
 
-	sample->core_pct_busy = core_pct;
+	core_pct = div64_u64(sample->aperf * 100, sample->mperf);
+
+	c0_pct = div64_u64(sample->mperf * 100, sample->tsc);
+	sample->freq = fp_toint(
+		mul_fp(int_tofp(cpu->pstate.max_pstate),
+			int_tofp(core_pct * 1000)));
+
+	sample->core_pct_busy = mul_fp(int_tofp(core_pct),
+				div_fp(int_tofp(c0_pct + 1), int_tofp(100)));
 }
 
 static inline void intel_pstate_sample(struct cpudata *cpu)