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Power management fixes for v4.13-rc6

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- Disable interrupts around reading IA32_APERF and IA32_MPERF in
    aperfmperf_snapshot_khz() (introduced recently) to avoid excessive
    delays between the reads that may result from interrupt handling
    (Doug Smythies).
 
  - Fix the comutation of the CPU frequency to be reported through the
    pstate_sample tracepoint in intel_pstate (Doug Smythies).
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Merge tag 'pm-4.13-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm

Pull power management fixes from Rafael Wysocki:
 "These fix two issues related to exposing the current CPU frequency to
  user space on x86.

  Specifics:

   - Disable interrupts around reading IA32_APERF and IA32_MPERF in
     aperfmperf_snapshot_khz() (introduced recently) to avoid excessive
     delays between the reads that may result from interrupt handling
     (Doug Smythies).

   - Fix the computation of the CPU frequency to be reported through the
     pstate_sample tracepoint in intel_pstate (Doug Smythies)"

* tag 'pm-4.13-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
  cpufreq: x86: Disable interrupts during MSRs reading
  cpufreq: intel_pstate: report correct CPU frequencies during trace
This commit is contained in:
Linus Torvalds 2017-08-17 14:21:18 -07:00
commit d33a2a9143
2 changed files with 4 additions and 2 deletions
Download patch file Download diff file Expand all files Collapse all files

3
arch/x86/kernel/cpu/aperfmperf.c
View file

@ -40,13 +40,16 @@ static void aperfmperf_snapshot_khz(void *dummy)
struct aperfmperf_sample *s = this_cpu_ptr(&samples);
ktime_t now = ktime_get();
s64 time_delta = ktime_ms_delta(now, s->time);
unsigned long flags;
/* Don't bother re-computing within the cache threshold time. */
if (time_delta < APERFMPERF_CACHE_THRESHOLD_MS)
return;
local_irq_save(flags);
rdmsrl(MSR_IA32_APERF, aperf);
rdmsrl(MSR_IA32_MPERF, mperf);
local_irq_restore(flags);
aperf_delta = aperf - s->aperf;
mperf_delta = mperf - s->mperf;

3
drivers/cpufreq/intel_pstate.c
View file

@ -1613,8 +1613,7 @@ static inline bool intel_pstate_sample(struct cpudata *cpu, u64 time)
static inline int32_t get_avg_frequency(struct cpudata *cpu)
{
return mul_ext_fp(cpu->sample.core_avg_perf,
cpu->pstate.max_pstate_physical * cpu->pstate.scaling);
return mul_ext_fp(cpu->sample.core_avg_perf, cpu_khz);
}
static inline int32_t get_avg_pstate(struct cpudata *cpu)