1. 01 Apr, 2016 1 commit
    • Rafael J. Wysocki's avatar
      intel_pstate: Avoid extra invocation of intel_pstate_sample() · febce40f
      Rafael J. Wysocki authored
      The initialization of intel_pstate for a given CPU involves populating
      the fields of its struct cpudata that represent the previous sample,
      but currently that is done in a problematic way.
      
      Namely, intel_pstate_init_cpu() makes an extra call to
      intel_pstate_sample() so it reads the current register values that
      will be used to populate the "previous sample" record during the
      next invocation of intel_pstate_sample().  However, after commit
      a4675fbc (cpufreq: intel_pstate: Replace timers with utilization
      update callbacks) that doesn't work for last_sample_time, because
      the time value is passed to intel_pstate_sample() as an argument now.
      Passing 0 to it from intel_pstate_init_cpu() is problematic, because
      that causes cpu->last_sample_time == 0 to be visible in
      get_target_pstate_use_performance() (and hence the extra
      cpu->last_sample_time > 0 check in there) and effectively allows
      the first invocation of intel_pstate_sample() from
      intel_pstate_update_util() to happen immediately after the
      initialization which may lead to a significant "turn on"
      effect in the governor algorithm.
      
      To mitigate that issue, rework the initialization to avoid the
      extra intel_pstate_sample() call from intel_pstate_init_cpu().
      Instead, make intel_pstate_sample() return false if it has been
      called with cpu->sample.time equal to zero, which will make
      intel_pstate_update_util() skip the sample in that case, and
      reset cpu->sample.time from intel_pstate_set_update_util_hook()
      to make the algorithm start properly every time the hook is set.
      Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
      febce40f
  2. 31 Mar, 2016 1 commit
    • Rafael J. Wysocki's avatar
      intel_pstate: Do not set utilization update hook too early · bb6ab52f
      Rafael J. Wysocki authored
      The utilization update hook in the intel_pstate driver is set too
      early, as it only should be set after the policy has been fully
      initialized by the core.  That may cause intel_pstate_update_util()
      to use incorrect data and put the CPUs into incorrect P-states as
      a result.
      
      To prevent that from happening, make intel_pstate_set_policy() set
      the utilization update hook instead of intel_pstate_init_cpu() so
      intel_pstate_update_util() only runs when all things have been
      initialized as appropriate.
      Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
      bb6ab52f
  3. 22 Mar, 2016 7 commits
  4. 19 Mar, 2016 2 commits
    • Richard Cochran's avatar
      cpufreq: acpi-cpufreq: Clean up hot plug notifier callback · ed72662a
      Richard Cochran authored
      This driver has two issues.  First, it tries to fiddle with the hot
      plugged CPU's MSR on the UP_PREPARE event, at a time when the CPU is
      not yet online.  Second, the driver sets the "boost-disable" bit for a
      CPU when going down, but does not clear the bit again if the CPU comes
      up again due to DOWN_FAILED.
      
      This patch fixes the issues by changing the driver to react to the
      ONLINE/DOWN_FAILED events instead of UP_PREPARE.  As an added benefit,
      the driver also becomes symmetric with respect to the hot plug
      mechanism.
      Signed-off-by: default avatarRichard Cochran <rcochran@linutronix.de>
      Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
      ed72662a
    • Rafael J. Wysocki's avatar
      intel_pstate: Do not call wrmsrl_on_cpu() with disabled interrupts · fdfdb2b1
      Rafael J. Wysocki authored
      After commit a4675fbc (cpufreq: intel_pstate: Replace timers with
      utilization update callbacks) wrmsrl_on_cpu() cannot be called in the
      intel_pstate_adjust_busy_pstate() path as that is executed with
      disabled interrupts.  However, atom_set_pstate() called from there
      via intel_pstate_set_pstate() uses wrmsrl_on_cpu() to update the
      IA32_PERF_CTL MSR which triggers the WARN_ON_ONCE() in
      smp_call_function_single().
      
      The reason why wrmsrl_on_cpu() is used by atom_set_pstate() is
      because intel_pstate_set_pstate() calling it is also invoked during
      the initialization and cleanup of the driver and in those cases it is
      not guaranteed to be run on the CPU that is being updated.  However,
      in the case when intel_pstate_set_pstate() is called by
      intel_pstate_adjust_busy_pstate(), wrmsrl() can be used to update
      the register safely.  Moreover, intel_pstate_set_pstate() already
      contains code that only is executed if the function is called by
      intel_pstate_adjust_busy_pstate() and there is a special argument
      passed to it because of that.
      
      To fix the problem at hand, rearrange the code taking the above
      observations into account.
      
      First, replace the ->set() callback in struct pstate_funcs with a
      ->get_val() one that will return the value to be written to the
      IA32_PERF_CTL MSR without updating the register.
      
      Second, split intel_pstate_set_pstate() into two functions,
      intel_pstate_update_pstate() to be called by
      intel_pstate_adjust_busy_pstate() that will contain all of the
      intel_pstate_set_pstate() code which only needs to be executed in
      that case and will use wrmsrl() to update the MSR (after obtaining
      the value to write to it from the ->get_val() callback), and
      intel_pstate_set_min_pstate() to be invoked during the
      initialization and cleanup that will set the P-state to the
      minimum one and will update the MSR using wrmsrl_on_cpu().
      
      Finally, move the code shared between intel_pstate_update_pstate()
      and intel_pstate_set_min_pstate() to a new static inline function
      intel_pstate_record_pstate() and make them both call it.
      
      Of course, that unifies the handling of the IA32_PERF_CTL MSR writes
      between Atom and Core.
      
      Fixes: a4675fbc (cpufreq: intel_pstate: Replace timers with utilization update callbacks)
      Reported-and-tested-by: default avatarJosh Boyer <jwboyer@fedoraproject.org>
      Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
      fdfdb2b1
  5. 18 Mar, 2016 1 commit
  6. 10 Mar, 2016 7 commits
  7. 09 Mar, 2016 21 commits