• Shilpasri G Bhat's avatar
    cpufreq: powernv: Report cpu frequency throttling · 09a972d1
    Shilpasri G Bhat authored
    The power and thermal safety of the system is taken care by an
    On-Chip-Controller (OCC) which is real-time subsystem embedded within
    the POWER8 processor. OCC continuously monitors the memory and core
    temperature, the total system power, state of power supply and fan.
    
    The cpu frequency can be throttled by OCC for the following reasons:
    1)If a processor crosses its power and temperature limit then OCC will
      lower its Pmax to reduce the frequency and voltage.
    2)If OCC crashes then the system is forced to Psafe frequency.
    3)If OCC fails to recover then the kernel is not allowed to do any
      further frequency changes and the chip will remain in Psafe.
    
    The user can see a drop in performance when frequency is throttled and
    is unaware of throttling. So detect and report such a condition, so
    the user can check the OCC status to reboot the system or check for
    power supply or fan failures.
    
    The current status of the core is read from Power Management Status
    Register(PMSR) to check if any of the throttling condition is occurred
    and the appropriate throttling message is reported.
    Signed-off-by: default avatarShilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>
    Reviewed-by: default avatarPreeti U Murthy <preeti@linux.vnet.ibm.com>
    Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
    09a972d1
powernv-cpufreq.c 11.5 KB