[PATCH v2 1/2] arch_topology: seed capacity_freq_ref with boost-aware max freq

[Ananthu C V]

capacity_freq_ref, the per-CPU frequency-invariance reference used by
schedutil, is seeded from policy->cpuinfo.max_freq at policy creation.
If boost frequencies are filtered out of the frequency table because
boost isn't yet enabled at boot, max_freq only reflects the non-boost
ceiling, so capacity_freq_ref never learns about boost frequencies for
the policy's lifetime. Enabling boost later raises policy->max, but
capacity_freq_ref stays stale, leaving schedutil unable to scale
utilization or target a frequency above the non-boost maximum.

Track the highest frequency in the table regardless of boost state
(max_table_freq) and seed capacity_freq_ref with max(cpuinfo.max_freq,
max_table_freq), so the invariance reference is boost-aware from boot
regardless of whether boost is currently enabled. Runtime enforcement,
still handled by policy->max, is unaffected.

Suggested-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Signed-off-by: Ananthu C V <ananthu.cv@xxxxxxxxxxxxxxxx>
---
 drivers/base/arch_topology.c | 3 ++-
 drivers/cpufreq/freq_table.c | 6 ++++++
 include/linux/cpufreq.h      | 1 +
 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
index 8c5e47c28d9a..da94f77441da 100644
--- a/drivers/base/arch_topology.c
+++ b/drivers/base/arch_topology.c
@@ -404,7 +404,8 @@ init_cpu_capacity_callback(struct notifier_block *nb,
 	cpumask_andnot(cpus_to_visit, cpus_to_visit, policy->related_cpus);
 
 	for_each_cpu(cpu, policy->related_cpus) {
-		per_cpu(capacity_freq_ref, cpu) = policy->cpuinfo.max_freq;
+		per_cpu(capacity_freq_ref, cpu) = max(policy->cpuinfo.max_freq,
+						      policy->cpuinfo.max_table_freq);
 		freq_inv_set_max_ratio(cpu,
 				       per_cpu(capacity_freq_ref, cpu) * HZ_PER_KHZ);
 	}
diff --git a/drivers/cpufreq/freq_table.c b/drivers/cpufreq/freq_table.c
index ea994647abc8..4984142dc08a 100644
--- a/drivers/cpufreq/freq_table.c
+++ b/drivers/cpufreq/freq_table.c
@@ -33,11 +33,15 @@ int cpufreq_frequency_table_cpuinfo(struct cpufreq_policy *policy)
 	struct cpufreq_frequency_table *pos, *table = policy->freq_table;
 	unsigned int min_freq = ~0;
 	unsigned int max_freq = 0;
+	unsigned int max_table_freq = 0;
 	unsigned int freq, i;
 
 	cpufreq_for_each_valid_entry_idx(pos, table, i) {
 		freq = pos->frequency;
 
+		if (freq > max_table_freq)
+			max_table_freq = freq;
+
 		if ((!cpufreq_boost_enabled() || !policy->boost_enabled)
 		    && (pos->flags & CPUFREQ_BOOST_FREQ))
 			continue;
@@ -57,6 +61,8 @@ int cpufreq_frequency_table_cpuinfo(struct cpufreq_policy *policy)
 	if (policy->cpuinfo.max_freq < max_freq)
 		policy->cpuinfo.max_freq = max_freq;
 
+	policy->cpuinfo.max_table_freq = max_table_freq;
+
 	if (min_freq == ~0)
 		return -EINVAL;
 	else
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index 35ce665edfd8..3f3b1380251a 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -45,6 +45,7 @@ enum cpufreq_table_sorting {
 struct cpufreq_cpuinfo {
 	unsigned int		max_freq;
 	unsigned int		min_freq;
+	unsigned int		max_table_freq; /* Highest valid frequency in the table */
 
 	/* in 10^(-9) s = nanoseconds */
 	unsigned int		transition_latency;

-- 
2.43.0