ACPI: CPPC: add sysfs entry for guaranteed performance

Expose the CPPC guaranteed performance as reported by the platform through
GuaranteedPerformanceRegister.

The current value is already read in cppc_get_perf_caps() and stored in
struct cppc_perf_caps (to be used by the intel_pstate driver), so only the
attribute itself needs to be defined.

Signed-off-by: Petr Tesařík <ptesarik@suse.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Author: ptesarik

drivers/acpi/cppc_acpi.c

@@ -160,6 +160,7 @@ show_cppc_data(cppc_get_perf_caps, cppc_perf_caps, highest_perf);
 show_cppc_data(cppc_get_perf_caps, cppc_perf_caps, lowest_perf);
 show_cppc_data(cppc_get_perf_caps, cppc_perf_caps, nominal_perf);
 show_cppc_data(cppc_get_perf_caps, cppc_perf_caps, lowest_nonlinear_perf);
+show_cppc_data(cppc_get_perf_caps, cppc_perf_caps, guaranteed_perf);
 show_cppc_data(cppc_get_perf_caps, cppc_perf_caps, lowest_freq);
 show_cppc_data(cppc_get_perf_caps, cppc_perf_caps, nominal_freq);
 
@@ -196,6 +197,7 @@ static struct attribute *cppc_attrs[] = {
 	&highest_perf.attr,
 	&lowest_perf.attr,
 	&lowest_nonlinear_perf.attr,
+	&guaranteed_perf.attr,
 	&nominal_perf.attr,
 	&nominal_freq.attr,
 	&lowest_freq.attr,