[PATCH v1 2/2] cpufreq: update capacity_freq_ref when the boost state changes

[Oleg Keri]

capacity_freq_ref is latched from policy->cpuinfo.max_freq by
init_cpu_capacity_callback() on CPUFREQ_CREATE_POLICY, and never
updated afterwards.

cpufreq_frequency_table_cpuinfo() excludes CPUFREQ_BOOST_FREQ entries
while boost is disabled, so on a system that boots with boost off the
latched value is the non-boost maximum.  Enabling boost later raises
policy->cpuinfo.max_freq but leaves capacity_freq_ref behind.

Two things then go wrong on arm64, where the AMU drives frequency
invariance.  amu_scale_freq_tick() caps the computed scale at
SCHED_CAPACITY_SCALE, so a CPU running above capacity_freq_ref
saturates at 1024: the scheduler cannot tell a boosted CPU from one at
the sustained maximum, and utilisation is underestimated.  And
arch_freq_get_on_cpu(), which reverses that computation, cannot report
more than capacity_freq_ref, so cpuinfo_avg_freq is pinned to the
non-boost maximum.

On a Snapdragon X2 Elite (Glymur) laptop with a 4032000 kHz sustained
and a 4723200 kHz boost OPP, cpuinfo_avg_freq reads exactly 4032000
while the CPU runs at 4723200; a fixed workload completes in 1.72 s
rather than the 2.01 s that frequency would imply.

Factor the update out of init_cpu_capacity_callback() into
topology_update_freq_ref() and call it from policy_set_boost(), which
is the common path for the global boost knob, the per-policy one, and
the CPU online path.

Signed-off-by: Oleg Keri <okerixx@xxxxxxxxx>
---
 arch/arm/include/asm/topology.h   |  1 +
 arch/arm64/include/asm/topology.h |  1 +
 arch/riscv/include/asm/topology.h |  1 +
 drivers/base/arch_topology.c      | 19 +++++++++++++------
 drivers/cpufreq/cpufreq.c         |  2 ++
 include/linux/arch_topology.h     |  1 +
 include/linux/cpufreq.h           |  7 +++++++
 7 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/arch/arm/include/asm/topology.h b/arch/arm/include/asm/topology.h
index ad36b6570067..a776a79885ee 100644
--- a/arch/arm/include/asm/topology.h
+++ b/arch/arm/include/asm/topology.h
@@ -11,6 +11,7 @@
 #ifndef CONFIG_BL_SWITCHER
 /* Replace task scheduler's default frequency-invariant accounting */
 #define arch_set_freq_scale topology_set_freq_scale
+#define arch_update_freq_ref topology_update_freq_ref
 #define arch_scale_freq_capacity topology_get_freq_scale
 #define arch_scale_freq_invariant topology_scale_freq_invariant
 #define arch_scale_freq_ref topology_get_freq_ref
diff --git a/arch/arm64/include/asm/topology.h b/arch/arm64/include/asm/topology.h
index b9eaf4ad7085..a4b96a7ee4a5 100644
--- a/arch/arm64/include/asm/topology.h
+++ b/arch/arm64/include/asm/topology.h
@@ -22,6 +22,7 @@ void update_freq_counters_refs(void);
 /* Replace task scheduler's default frequency-invariant accounting */
 #define arch_scale_freq_tick topology_scale_freq_tick
 #define arch_set_freq_scale topology_set_freq_scale
+#define arch_update_freq_ref topology_update_freq_ref
 #define arch_scale_freq_capacity topology_get_freq_scale
 #define arch_scale_freq_invariant topology_scale_freq_invariant
 #define arch_scale_freq_ref topology_get_freq_ref
diff --git a/arch/riscv/include/asm/topology.h b/arch/riscv/include/asm/topology.h
index fe1a8bf6902d..a363d72c174f 100644
--- a/arch/riscv/include/asm/topology.h
+++ b/arch/riscv/include/asm/topology.h
@@ -11,6 +11,7 @@
 /* Replace task scheduler's default frequency-invariant accounting */
 #define arch_scale_freq_tick		topology_scale_freq_tick
 #define arch_set_freq_scale		topology_set_freq_scale
+#define arch_update_freq_ref		topology_update_freq_ref
 #define arch_scale_freq_capacity	topology_get_freq_scale
 #define arch_scale_freq_invariant	topology_scale_freq_invariant
 #define arch_scale_freq_ref		topology_get_freq_ref
diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
index 8c5e47c28d9a..79eb1681065d 100644
--- a/drivers/base/arch_topology.c
+++ b/drivers/base/arch_topology.c
@@ -317,6 +317,18 @@ bool __init topology_parse_cpu_capacity(struct device_node *cpu_node, int cpu)
 	return !ret;
 }
 
+void topology_update_freq_ref(const struct cpumask *cpus, unsigned int max_freq)
+{
+	int cpu;
+
+	for_each_cpu(cpu, cpus) {
+		per_cpu(capacity_freq_ref, cpu) = max_freq;
+		freq_inv_set_max_ratio(cpu,
+				       per_cpu(capacity_freq_ref, cpu) * HZ_PER_KHZ);
+	}
+}
+EXPORT_SYMBOL_GPL(topology_update_freq_ref);
+
 void __weak freq_inv_set_max_ratio(int cpu, u64 max_rate)
 {
 }
@@ -392,7 +404,6 @@ init_cpu_capacity_callback(struct notifier_block *nb,
 			   void *data)
 {
 	struct cpufreq_policy *policy = data;
-	int cpu;
 
 	if (val != CPUFREQ_CREATE_POLICY)
 		return 0;
@@ -403,11 +414,7 @@ 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;
-		freq_inv_set_max_ratio(cpu,
-				       per_cpu(capacity_freq_ref, cpu) * HZ_PER_KHZ);
-	}
+	topology_update_freq_ref(policy->related_cpus, policy->cpuinfo.max_freq);
 
 	if (cpumask_empty(cpus_to_visit)) {
 		if (raw_capacity) {
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 0d0df986fa3d..289649baa061 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -594,6 +594,8 @@ static int policy_set_boost(struct cpufreq_policy *policy, bool enable)
 		return ret;
 	}
 
+	arch_update_freq_ref(policy->related_cpus, policy->cpuinfo.max_freq);
+
 	return 0;
 }
 
diff --git a/include/linux/arch_topology.h b/include/linux/arch_topology.h
index ebd7f8935f96..4974f5e1a7fe 100644
--- a/include/linux/arch_topology.h
+++ b/include/linux/arch_topology.h
@@ -31,6 +31,7 @@ static inline unsigned long topology_get_freq_scale(int cpu)
 
 void topology_set_freq_scale(const struct cpumask *cpus, unsigned long cur_freq,
 			     unsigned long max_freq);
+void topology_update_freq_ref(const struct cpumask *cpus, unsigned int max_freq);
 bool topology_scale_freq_invariant(void);
 
 enum scale_freq_source {
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index 35ce665edfd8..5b904e13eb21 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -1235,6 +1235,13 @@ void arch_set_freq_scale(const struct cpumask *cpus,
 }
 #endif
 
+#ifndef arch_update_freq_ref
+static __always_inline
+void arch_update_freq_ref(const struct cpumask *cpus, unsigned int max_freq)
+{
+}
+#endif
+
 /* the following are really really optional */
 extern struct freq_attr cpufreq_freq_attr_scaling_available_freqs;
 extern struct freq_attr cpufreq_freq_attr_scaling_boost_freqs;
-- 
2.55.0