Commit 8478f539 authored Nov 20, 2015 by Prarit Bhargava Committed by Rafael J. Wysocki Nov 23, 2015

cpufreq: intel_pstate: Fix limits->max_policy_pct rounding error



I have a Intel (6,63) processor with a "marketing" frequency (from
/proc/cpuinfo) of 2100MHz, and a max turbo frequency of 2600MHz.  I
can execute

cpupower frequency-set -g powersave --min 1200MHz --max 2100MHz

and the max_freq_pct is set to 80.  When adding load to the system I noticed
that the cpu frequency only reached 2000MHZ and not 2100MHz as expected.

This is because limits->max_policy_pct is calculated as 2100 * 100 /2600 = 80.7
and is rounded down to 80 when it should be rounded up to 81.  This patch
adds a DIV_ROUND_UP() which will return the correct value.

Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

parent f344dae0

drivers/cpufreq/intel_pstate.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -1108,7 +1108,8 @@ static int intel_pstate_set_policy(struct cpufreq_policy *policy)
		limits = &powersave_limits;
		limits->min_policy_pct = (policy->min * 100) / policy->cpuinfo.max_freq;
		limits->min_policy_pct = clamp_t(int, limits->min_policy_pct, 0 , 100);
		limits->max_policy_pct = (policy->max * 100) / policy->cpuinfo.max_freq;
		limits->max_policy_pct = DIV_ROUND_UP(policy->max * 100,
		policy->cpuinfo.max_freq);
		limits->max_policy_pct = clamp_t(int, limits->max_policy_pct, 0 , 100);

		/* Normalize user input to [min_policy_pct, max_policy_pct] */