1. 13 Apr, 2014 1 commit
    • Mikulas Patocka's avatar
      powernow-k6: disable cache when changing frequency · 3389f243
      Mikulas Patocka authored
      commit e20e1d0a upstream.
      
      I found out that a system with k6-3+ processor is unstable during network
      server load. The system locks up or the network card stops receiving. The
      reason for the instability is the CPU frequency scaling.
      
      During frequency transition the processor is in "EPM Stop Grant" state.
      The documentation says that the processor doesn't respond to inquiry
      requests in this state. Consequently, coherency of processor caches and
      bus master devices is not maintained, causing the system instability.
      
      This patch flushes the cache during frequency transition. It fixes the
      instability.
      
      Other minor changes:
      * u64 invalue changed to unsigned long because the variable is 32-bit
      * move the logic to set the multiplier to a separate function
        powernow_k6_set_cpu_multiplier
      * preserve lower 5 bits of the powernow port instead of 4 (the voltage
        field has 5 bits)
      * mask interrupts when reading the multiplier, so that the port is not
        open during other activity (running other kernel code with the port open
        shouldn't cause any misbehavior, but we should better be safe and keep
        the port closed)
      
      This patch should be backported to all stable kernels. If it doesn't
      apply cleanly, change it, or ask me to change it.
      Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
      Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
      Signed-off-by: default avatarJiri Slaby <jslaby@suse.cz>
      3389f243
  2. 03 Apr, 2014 39 commits