[PATCH v4 7/7] arm64/amu: use capacity_ref_freq to set AMU ratio

Vincent Guittot
2023-10-27T08:04:23Z

Use the new capacity_ref_freq to set the ratio that is used by AMU for
computing the arch_scale_freq_capacity().
This helps to keep everything aligned using the same reference for
computing CPUs capacity.

The default value of the ratio (stored in per_cpu(arch_max_freq_scale)
ensures that arch_scale_freq_capacity() returns max capacity until it is
set to its correct value with the cpu capacity and capacity_ref_freq.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
---
arch/arm64/kernel/topology.c | 26 ++++++++++++++------------
drivers/base/arch_topology.c | 12 +++++++++++-
include/linux/arch_topology.h | 1 +
3 files changed, 26 insertions(+), 13 deletions(-)

diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
index 817d788cd866..626031076b75 100644
--- a/arch/arm64/kernel/topology.c
+++ b/arch/arm64/kernel/topology.c
@@ -82,7 +82,12 @@ int __init parse_acpi_topology(void)
#undef pr_fmt
#define pr_fmt(fmt) "AMU: " fmt

-static DEFINE_PER_CPU_READ_MOSTLY(unsigned long, arch_max_freq_scale);
+/*
+ * Ensure that amu_scale_freq_tick() will return SCHED_CAPACITY_SCALE until
+ * the CPU capacity and its assosciated frequency have been correctly
+ * initialized.
+ */
+static DEFINE_PER_CPU_READ_MOSTLY(unsigned long, arch_max_freq_scale) = 1UL << (2 * SCHED_CAPACITY_SHIFT);
static DEFINE_PER_CPU(u64, arch_const_cycles_prev);
static DEFINE_PER_CPU(u64, arch_core_cycles_prev);
static cpumask_var_t amu_fie_cpus;
@@ -112,14 +117,14 @@ static inline bool freq_counters_valid(int cpu)
return true;
}

-static int freq_inv_set_max_ratio(int cpu, u64 max_rate, u64 ref_rate)
+void freq_inv_set_max_ratio(int cpu, u64 max_rate)
{
- u64 ratio;
+ u64 ratio, ref_rate = arch_timer_get_rate();

if (unlikely(!max_rate || !ref_rate)) {
- pr_debug("CPU%d: invalid maximum or reference frequency.\n",
+ WARN_ONCE(1, "CPU%d: invalid maximum or reference frequency.\n",
cpu);
- return -EINVAL;
+ return;
}

/*
@@ -139,12 +144,12 @@ static int freq_inv_set_max_ratio(int cpu, u64 max_rate, u64 ref_rate)
ratio = div64_u64(ratio, max_rate);
if (!ratio) {
WARN_ONCE(1, "Reference frequency too low.\n");
- return -EINVAL;
+ return;
}

- per_cpu(arch_max_freq_scale, cpu) = (unsigned long)ratio;
+ WRITE_ONCE(per_cpu(arch_max_freq_scale, cpu), (unsigned long)ratio);

- return 0;
+ return;
}

static void amu_scale_freq_tick(void)
@@ -195,10 +200,7 @@ static void amu_fie_setup(const struct cpumask *cpus)
return;

for_each_cpu(cpu, cpus) {
- if (!freq_counters_valid(cpu) ||
- freq_inv_set_max_ratio(cpu,
- cpufreq_get_hw_max_freq(cpu) * 1000ULL,
- arch_timer_get_rate()))
+ if (!freq_counters_valid(cpu))
return;
}

diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
index d4bef370feb3..3cba7dc753b3 100644
--- a/drivers/base/arch_topology.c
+++ b/drivers/base/arch_topology.c
@@ -344,6 +344,10 @@ bool __init topology_parse_cpu_capacity(struct device_node *cpu_node, int cpu)
return !ret;
}

+void __weak freq_inv_set_max_ratio(int cpu, u64 max_rate)
+{
+}
+
#ifdef CONFIG_ACPI_CPPC_LIB
#include <acpi/cppc_acpi.h>

@@ -381,6 +385,9 @@ void topology_init_cpu_capacity_cppc(void)
}

for_each_possible_cpu(cpu) {
+ freq_inv_set_max_ratio(cpu,
+ per_cpu(capacity_ref_freq, cpu) * HZ_PER_KHZ);
+
capacity = raw_capacity[cpu];
capacity = div64_u64(capacity << SCHED_CAPACITY_SHIFT,
capacity_scale);
@@ -422,8 +429,11 @@ 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)
+ for_each_cpu(cpu, policy->related_cpus) {
per_cpu(capacity_ref_freq, cpu) = policy->cpuinfo.max_freq;
+ freq_inv_set_max_ratio(cpu,
+ per_cpu(capacity_ref_freq, cpu) * HZ_PER_KHZ);
+ }

if (cpumask_empty(cpus_to_visit)) {
topology_normalize_cpu_scale();
diff --git a/include/linux/arch_topology.h b/include/linux/arch_topology.h
index 38ca6c76af56..ffdf0b7c55fa 100644
--- a/include/linux/arch_topology.h
+++ b/include/linux/arch_topology.h
@@ -99,6 +99,7 @@ void update_siblings_masks(unsigned int cpu);
void remove_cpu_topology(unsigned int cpuid);
void reset_cpu_topology(void);
int parse_acpi_topology(void);
+void freq_inv_set_max_ratio(int cpu, u64 max_rate);
#endif

#endif /* _LINUX_ARCH_TOPOLOGY_H_ */
--
2.34.1