• Srinivas Pandruvada's avatar
    cpufreq: intel_pstate: Enforce _PPC limits · 9522a2ff
    Srinivas Pandruvada authored
    Use ACPI _PPC notification to limit max P state driver will request.
    ACPI _PPC change notification is sent by BIOS to limit max P state
    in several cases:
    - Reduce impact of platform thermal condition
    - When Config TDP feature is used, a changed _PPC is sent to
    follow TDP change
    - Remote node managers in server want to control platform power
    via baseboard management controller (BMC)
    This change registers with ACPI processor performance lib so that
    _PPC changes are notified to cpufreq core, which in turns will
    result in call to .setpolicy() callback. Also the way _PSS
    table identifies a turbo frequency is not compatible to max turbo
    frequency in intel_pstate, so the very first entry in _PSS needs
    to be adjusted.
    This feature can be turned on by using kernel parameters:
    Signed-off-by: default avatarSrinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
    [ rjw: Minor cleanups ]
    Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
kernel-parameters.txt 153 KB