| Message ID | 9094016.kKgRgCK7kp@kreacher |
|---|---|
| State | Superseded |
| Headers | show |
| Series |
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| Related | show |
On Thu, 2020-08-27 at 17:14 +0200, Rafael J. Wysocki wrote: > From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com> > > Modify the EPP sysfs interface to reject attempts to change the EPP > to values different from 0 ("performance") in the active mode with > the "performance" policy (ie. scaling_governor set to "performance"), > to avoid situations in which the kernel appears to discard data > passed to it via the EPP sysfs attribute. > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> This one looks good to me, thanks. Reviewed-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
diff --git a/Documentation/admin-guide/pm/intel_pstate.rst b/Documentation/admin-guide/pm/intel_pstate.rst index cdd1a9a7f9a2..5072e7064d13 100644 --- a/Documentation/admin-guide/pm/intel_pstate.rst +++ b/Documentation/admin-guide/pm/intel_pstate.rst @@ -123,7 +123,9 @@ Energy-Performance Bias (EPB) knob (otherwise), which means that the processor's internal P-state selection logic is expected to focus entirely on performance. This will override the EPP/EPB setting coming from the ``sysfs`` interface -(see `Energy vs Performance Hints`_ below). +(see `Energy vs Performance Hints`_ below). Moreover, any attempts to change +the EPP/EPB to a value different from 0 ("performance") via ``sysfs`` in this +configuration will be rejected. Also, in this configuration the range of P-states available to the processor's internal P-state selection logic is always restricted to the upper boundary diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c index e540448e0bd0..b308c39b6204 100644 --- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c @@ -684,6 +684,14 @@ static int intel_pstate_set_energy_pref_index(struct cpudata *cpu_data, else if (epp == -EINVAL) epp = epp_values[pref_index - 1]; + /* + * To avoid confusion, refuse to set EPP to any values different + * from 0 (performance) if the current policy is "performance", + * because those values would be overridden. + */ + if (epp > 0 && cpu_data->policy == CPUFREQ_POLICY_PERFORMANCE) + return -EBUSY; + ret = intel_pstate_set_epp(cpu_data, epp); } else { if (epp == -EINVAL)