@@ -512,6 +512,7 @@ struct acpi_madt_generic_interrupt *acpi_cpu_get_madt_gicc(int cpu)
{
return &cpu_madt_gicc[cpu];
}
+EXPORT_SYMBOL(acpi_cpu_get_madt_gicc);
/*
* acpi_map_gic_cpu_interface - parse processor MADT entry
@@ -422,12 +422,66 @@ static unsigned int cppc_cpufreq_get_transition_delay_us(unsigned int cpu)
return cppc_get_transition_latency(cpu) / NSEC_PER_USEC;
}
+static bool efficiency_class_populated;
+static DEFINE_PER_CPU(unsigned int, efficiency_class);
+
+static int populate_efficiency_class(void)
+{
+ unsigned int min = UINT_MAX, max = 0, class;
+ struct acpi_madt_generic_interrupt *gicc;
+ int cpu;
+
+ for_each_possible_cpu(cpu) {
+ gicc = acpi_cpu_get_madt_gicc(cpu);
+ if (!gicc)
+ return -ENODEV;
+
+ per_cpu(efficiency_class, cpu) = gicc->efficiency_class;
+ min = min_t(unsigned int, min, gicc->efficiency_class);
+ max = max_t(unsigned int, max, gicc->efficiency_class);
+ }
+
+ if (min == max) {
+ pr_debug("Efficiency classes are all equal (=%d). "
+ "No EM registered", max);
+ return -EINVAL;
+ }
+
+ /*
+ * Squeeze efficiency class values on [0:#efficiency_class-1].
+ * Values are per spec in [0:255].
+ */
+ for (class = 0; class < 256; class++) {
+ unsigned int new_min, curr;
+
+ new_min = UINT_MAX;
+ for_each_possible_cpu(cpu) {
+ curr = per_cpu(efficiency_class, cpu);
+ if (curr == min)
+ per_cpu(efficiency_class, cpu) = class;
+ else if (curr > min)
+ new_min = min(new_min, curr);
+ }
+
+ if (new_min == UINT_MAX)
+ break;
+ min = new_min;
+ }
+
+ efficiency_class_populated = true;
+ return 0;
+}
+
#else
static unsigned int cppc_cpufreq_get_transition_delay_us(unsigned int cpu)
{
return cppc_get_transition_latency(cpu) / NSEC_PER_USEC;
}
+static int populate_efficiency_class(void)
+{
+ return 0;
+}
#endif
@@ -757,6 +811,7 @@ static int __init cppc_cpufreq_init(void)
cppc_check_hisi_workaround();
cppc_freq_invariance_init();
+ populate_efficiency_class();
ret = cpufreq_register_driver(&cppc_cpufreq_driver);
if (ret)
In ACPI, describing power efficiency of CPUs can be done through the following arm specific field: ACPI 6.4, s5.2.12.14 'GIC CPU Interface (GICC) Structure', 'Processor Power Efficiency Class field': Describes the relative power efficiency of the associated pro- cessor. Lower efficiency class numbers are more efficient than higher ones (e.g. efficiency class 0 should be treated as more efficient than efficiency class 1). However, absolute values of this number have no meaning: 2 isn’t necessarily half as efficient as 1. The efficiency_class field is stored in the GicC structure of the ACPI MADT table and it's currently supported in Linux for arm64 only. Thus, this new functionality is introduced for arm64 only. To allow the cppc_cpufreq driver to know and preprocess the efficiency_class values of all the CPUs, add a per_cpu efficiency_class variable to store them. Also add a static efficiency_class_populated to let the driver know efficiency_class values are usable and register an artificial Energy Model (EM) based on normalized class values. At least 2 different efficiency classes must be present, otherwise there is no use in creating an Energy Model. The efficiency_class values are squeezed in [0:#efficiency_class-1] while conserving the order. For instance, efficiency classes of: [111, 212, 250] will be mapped to: [0 (was 111), 1 (was 212), 2 (was 250)]. Each policy being independently registered in the driver, populating the per_cpu efficiency_class is done only once at the driver initialization. This prevents from having each policy re-searching the efficiency_class values of other CPUs. The patch also exports acpi_cpu_get_madt_gicc() to fetch the GicC structure of the ACPI MADT table for each CPU. Signed-off-by: Pierre Gondois <Pierre.Gondois@arm.com> --- arch/arm64/kernel/smp.c | 1 + drivers/cpufreq/cppc_cpufreq.c | 55 ++++++++++++++++++++++++++++++++++ 2 files changed, 56 insertions(+)