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cpufreq: intel_pstate: Fix ->set_policy() interface for no_turbo

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When turbo is disabled, the ->set_policy() interface is broken.

For example, when turbo is disabled and cpuinfo.max = 2900000 (full
max turbo frequency), setting the limits results in frequency less
than the requested one:
Set 1000000 KHz results in 0700000 KHz
Set 1500000 KHz results in 1100000 KHz
Set 2000000 KHz results in  1500000 KHz

This is because the limits->max_perf fraction is calculated using
the max turbo frequency as the reference, but when the max P-State is
capped in intel_pstate_get_min_max(), the reference is not the max
turbo P-State. This results in reducing max P-State.

One option is to always use max turbo as reference for calculating
limits. But this will not be correct. By definition the intel_pstate
sysfs limits, shows percentage of available performance. So when
BIOS has disabled turbo, the available performance is max non turbo.
So the max_perf_pct should still show 100%.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
[ rjw : Subject & changelog, rewrite in fewer lines of code ]
Cc: All applicable <stable@vger.kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Srinivas Pandruvada 2016-06-07 17:38:53 -07:00 committed by Rafael J. Wysocki
parent 2c2c1af449
commit 983e600e88
1 changed files with 5 additions and 2 deletions
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7
drivers/cpufreq/intel_pstate.c
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@ -1561,8 +1561,11 @@ static int intel_pstate_cpu_init(struct cpufreq_policy *policy)
/* cpuinfo and default policy values */
policy->cpuinfo.min_freq = cpu->pstate.min_pstate * cpu->pstate.scaling;
policy->cpuinfo.max_freq =
cpu->pstate.turbo_pstate * cpu->pstate.scaling;
update_turbo_state();
policy->cpuinfo.max_freq = limits->turbo_disabled ?
cpu->pstate.max_pstate : cpu->pstate.turbo_pstate;
policy->cpuinfo.max_freq *= cpu->pstate.scaling;
intel_pstate_init_acpi_perf_limits(policy);
policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL;
cpumask_set_cpu(policy->cpu, policy->cpus);