[PATCH v2 2/2] cpufreq: intel_pstate: Conditional frequency invariant accounting

[Giovanni Gherdovich]

From: Srinivas Pandruvada <srinivas.pandruvada@xxxxxxxxxxxxxxx>

intel_pstate has two operating modes: active and passive. In "active"
mode, the in-built scaling governor is used and in "passive" mode,
the driver can be used with any governor like "schedutil". In "active"
mode the utilization values from schedutil is not used and there is
a requirement from high performance computing use cases, not to read
any APERF/MPERF MSRs. In this case no need to use CPU cycles for
frequency invariant accounting by reading APERF/MPERF MSRs.
With this change frequency invariant account is only enabled in
"passive" mode.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@xxxxxxxxxxxxxxx>
Signed-off-by: Giovanni Gherdovich <ggherdovich@xxxxxxx>
---
 drivers/cpufreq/intel_pstate.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 9f02de9a1b47..c7d9149e99ee 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -2493,6 +2493,8 @@ static int intel_pstate_register_driver(struct cpufreq_driver *driver)
 {
 	int ret;
 
+	x86_arch_scale_freq_tick_disable();
+
 	memset(&global, 0, sizeof(global));
 	global.max_perf_pct = 100;
 
@@ -2505,6 +2507,9 @@ static int intel_pstate_register_driver(struct cpufreq_driver *driver)
 
 	global.min_perf_pct = min_perf_pct_min();
 
+	if (driver == &intel_cpufreq)
+		x86_arch_scale_freq_tick_enable();
+
 	return 0;
 }
 
-- 
2.16.4