ACPI x86: Make aperf/mperf MSR access in acpi_cpufreq read_only

Do not write zeroes to APERF and MPERF by ondemand governor. With this
change, other users can share these MSRs for reads.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 10 insertions, 5 deletions

diff --git a/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c b/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
index 340bdbebba07..9d3af380c6bd 100644
--- a/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
+++ b/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
@@ -68,6 +68,7 @@ struct acpi_cpufreq_data {
         unsigned int max_freq;
         unsigned int resume;
         unsigned int cpu_feature;
+        u64 saved_aperf, saved_mperf;
 };
 
 static DEFINE_PER_CPU(struct acpi_cpufreq_data *, drv_data);
@@ -259,9 +260,6 @@ static long read_measured_perf_ctrs(void *_cur)
         rdmsr(MSR_IA32_APERF, cur->aperf.split.lo, cur->aperf.split.hi);
         rdmsr(MSR_IA32_MPERF, cur->mperf.split.lo, cur->mperf.split.hi);
 
-        wrmsr(MSR_IA32_APERF, 0, 0);
-        wrmsr(MSR_IA32_MPERF, 0, 0);
-
         return 0;
 }
 
@@ -281,13 +279,20 @@ static long read_measured_perf_ctrs(void *_cur)
 static unsigned int get_measured_perf(struct cpufreq_policy *policy,
                                       unsigned int cpu)
 {
-        struct perf_pair cur;
+        struct perf_pair readin, cur;
         unsigned int perf_percent;
         unsigned int retval;
 
-        if (!work_on_cpu(cpu, read_measured_perf_ctrs, &cur))
+        if (!work_on_cpu(cpu, read_measured_perf_ctrs, &readin))
                 return 0;
 
+        cur.aperf.whole = readin.aperf.whole -
+                                per_cpu(drv_data, cpu)->saved_aperf;
+        cur.mperf.whole = readin.mperf.whole -
+                                per_cpu(drv_data, cpu)->saved_mperf;
+        per_cpu(drv_data, cpu)->saved_aperf = readin.aperf.whole;
+        per_cpu(drv_data, cpu)->saved_mperf = readin.mperf.whole;
+
 #ifdef __i386__
         /*
          * We dont want to do 64 bit divide with 32 bit kernel