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    Subject[PATCH 3.16 155/305] cpufreq: intel_pstate: Fix ->set_policy() interface for no_turbo
    3.16.37-rc1 review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>

    commit 983e600e88835f0321d1a0ea06f52d48b7b5a544 upstream.

    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 ]
    Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
    [bwh: Backported to 3.16:
    - limits is a perf_limits structure, not a pointer to it
    - Adjust context]
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    drivers/cpufreq/intel_pstate.c | 7 +++++--
    1 file changed, 5 insertions(+), 2 deletions(-)

    --- a/drivers/cpufreq/intel_pstate.c
    +++ b/drivers/cpufreq/intel_pstate.c
    @@ -877,8 +877,11 @@ static int intel_pstate_cpu_init(struct

    /* 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;
    +
    policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL;
    cpumask_set_cpu(policy->cpu, policy->cpus);

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