With the Frequency Invariance Engine (FIE) being already wired up with
sched tick and making use of relevant (core counter and constant
counter) AMU counters, getting the current frequency for a given CPU
on supported platforms, can be achieved by utilizing the frequency scale
factor which reflects an average CPU frequency for the last tick period
length.
Suggested-by: Ionela Voinescu <ionela.voinescu@xxxxxxx>
Signed-off-by: Beata Michalska <beata.michalska@xxxxxxx>
Reviewed-by: Sudeep Holla <sudeep.holla@xxxxxxx>
---
Notes:
Due to [1], if merged, there might be a need to modify the patch to
accommodate changes [1] introduces:
freq = cpufreq_get_hw_max_freq(cpu) >> SCHED_CAPACITY_SHIFT
to
freq = per_cpu(capacity_freq_ref, cpu); >> SCHED_CAPACITY_SHIFT
[1]
https://lore.kernel.org/linux-arm-kernel/20231121154349.GA1938@willie-the-truck/T/#mcb018d076dbce6f60ed2779634a9b6ffe622641e
arch/arm64/kernel/topology.c | 39 ++++++++++++++++++++++++++++++++++++
1 file changed, 39 insertions(+)
diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
index 615c1a20129f..ae2445f6e7da 100644
--- a/arch/arm64/kernel/topology.c
+++ b/arch/arm64/kernel/topology.c
@@ -17,6 +17,7 @@
#include <linux/cpufreq.h>
#include <linux/init.h>
#include <linux/percpu.h>
+#include <linux/sched/isolation.h>
#include <asm/cpu.h>
#include <asm/cputype.h>
@@ -186,6 +187,44 @@ static void amu_scale_freq_tick(void)
this_cpu_write(arch_freq_scale, (unsigned long)scale);
}
+unsigned int arch_freq_get_on_cpu(int cpu)
+{
+ unsigned int freq;
+ u64 scale;
+
+ if (!cpumask_test_cpu(cpu, amu_fie_cpus))
+ return 0;
+
+ /*
+ * For those CPUs that are in full dynticks mode, try an alternative
+ * source for the counters (and thus freq scale),
+ * if available for given policy
+ */
+ if (!housekeeping_cpu(cpu, HK_TYPE_TICK)) {
+ struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
+ int ref_cpu = nr_cpu_ids;
+
+ if (cpumask_intersects(housekeeping_cpumask(HK_TYPE_TICK),
+ policy->cpus))
+ ref_cpu = cpumask_nth_and(cpu, policy->cpus,
+ housekeeping_cpumask(HK_TYPE_TICK));
+ cpufreq_cpu_put(policy);
+ if (ref_cpu >= nr_cpu_ids)
+ return 0;
+ cpu = ref_cpu;
+ }
+
+ /*
+ * Reversed computation to the one used to determine
+ * the arch_freq_scale value
+ * (see amu_scale_freq_tick for details)
+ */
+ scale = per_cpu(arch_freq_scale, cpu);
+ freq = cpufreq_get_hw_max_freq(cpu) >> SCHED_CAPACITY_SHIFT;
+ freq *= scale;
+ return freq;
+}
+
static struct scale_freq_data amu_sfd = {
.source = SCALE_FREQ_SOURCE_ARCH,
.set_freq_scale = amu_scale_freq_tick,
--
2.25.1
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel