• Srinivas Pandruvada's avatar
    cpufreq: intel_pstate: Fix ->set_policy() interface for no_turbo · 983e600e
    Srinivas Pandruvada authored
    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: default avatarSrinivas 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: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
    983e600e
intel_pstate.c 46.9 KB