| Message ID | 1448063277-12446-3-git-send-email-prarit@redhat.com (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Delegated to: | Rafael Wysocki |
| Headers | show |
On Fri, 2015-11-20 at 18:47 -0500, Prarit Bhargava wrote: > A rounding error was found in the calculation of limits->max_perf > in intel_pstate_set_policy(), which is used to calculate the max and min > pstate values in intel_pstate_get_min_max(). In that code, > limits->max_perf is truncated to 2 hex digits such that, for example, > 0x169 was incorrectly calculated to 0x16 instead of 0x17. This resulted in > the pstate being set one level too low. This patch rounds the value of > limits->max_perf up instead of down so that the correct max pstate can > be reached. > > Cc: Srinivas Pandruvada <srinivas.pandruvada@intel.com> > Cc: Len Brown <len.brown@intel.com> > Cc: Alexandra Yates <alexandra.yates@intel.com> > Cc: Kristen Carlson Accardi <kristen@linux.intel.com> > Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> > Cc: Viresh Kumar <viresh.kumar@linaro.org> > Cc: linux-pm@vger.kernel.org > Signed-off-by: Prarit Bhargava <prarit@redhat.com> Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> > --- > drivers/cpufreq/intel_pstate.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c > index eb75053..8ad1f95 100644 > --- a/drivers/cpufreq/intel_pstate.c > +++ b/drivers/cpufreq/intel_pstate.c > @@ -1121,6 +1121,7 @@ static int intel_pstate_set_policy(struct cpufreq_policy *policy) > limits->max_sysfs_pct); > limits->max_perf_pct = max(limits->min_policy_pct, > limits->max_perf_pct); > + limits->max_perf = round_up(limits->max_perf, 8); > > /* Make sure min_perf_pct <= max_perf_pct */ > limits->min_perf_pct = min(limits->max_perf_pct, limits->min_perf_pct);
diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c index eb75053..8ad1f95 100644 --- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c @@ -1121,6 +1121,7 @@ static int intel_pstate_set_policy(struct cpufreq_policy *policy) limits->max_sysfs_pct); limits->max_perf_pct = max(limits->min_policy_pct, limits->max_perf_pct); + limits->max_perf = round_up(limits->max_perf, 8); /* Make sure min_perf_pct <= max_perf_pct */ limits->min_perf_pct = min(limits->max_perf_pct, limits->min_perf_pct);
A rounding error was found in the calculation of limits->max_perf in intel_pstate_set_policy(), which is used to calculate the max and min pstate values in intel_pstate_get_min_max(). In that code, limits->max_perf is truncated to 2 hex digits such that, for example, 0x169 was incorrectly calculated to 0x16 instead of 0x17. This resulted in the pstate being set one level too low. This patch rounds the value of limits->max_perf up instead of down so that the correct max pstate can be reached. Cc: Srinivas Pandruvada <srinivas.pandruvada@intel.com> Cc: Len Brown <len.brown@intel.com> Cc: Alexandra Yates <alexandra.yates@intel.com> Cc: Kristen Carlson Accardi <kristen@linux.intel.com> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> Cc: Viresh Kumar <viresh.kumar@linaro.org> Cc: linux-pm@vger.kernel.org Signed-off-by: Prarit Bhargava <prarit@redhat.com> --- drivers/cpufreq/intel_pstate.c | 1 + 1 file changed, 1 insertion(+)