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>

diff --git a/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c b/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
index 340bdbebba0766aa5d076d8fe0a77a19d26b66f0..9d3af380c6bdfc41a847578ae8eb78a0a151bc38 100644 (file)
--- 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