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cpufreq: intel_pstate: Fix limits->max_policy_pct rounding error

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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>
This commit is contained in:
Prarit Bhargava 2015-11-20 18:47:56 -05:00 committed by Rafael J. Wysocki
parent f344dae0fe
commit 8478f53946
1 changed files with 2 additions and 1 deletions
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3
drivers/cpufreq/intel_pstate.c
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@ -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] */