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    SubjectRe: [RFC v3 6/6] arm64/amu: use capacity_ref_freq to set AMU ratio
    On Mon, 23 Oct 2023 at 22:58, Ionela Voinescu <ionela.voinescu@arm.com> wrote:
    >
    > Hi,
    >
    > On Wednesday 18 Oct 2023 at 18:25:40 (+0200), Vincent Guittot wrote:
    > > 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 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 | 18 ++++++++++--------
    > > drivers/base/arch_topology.c | 14 ++++++++++++--
    > > include/linux/arch_topology.h | 1 +
    > > 3 files changed, 23 insertions(+), 10 deletions(-)
    > >
    > > diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
    > > index 817d788cd866..0f8f6e90c46d 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_SHIFT until
    > > + * the CPU capacity and its assosciated frequency have been correctly
    > > + * initialized.
    >
    > s/SCHED_CAPACITY_SHIFT/SCHED_CAPACITY_SCALE
    >
    > > + */
    > > +static DEFINE_PER_CPU_READ_MOSTLY(unsigned long, arch_max_freq_scale) = (2 * SCHED_CAPACITY_SHIFT);
    >
    > It should be 1UL << (2 * SCHED_CAPACITY_SHIFT).

    yes

    >
    > > 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;
    > > @@ -112,9 +117,9 @@ 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)
    > > +int 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",
    > > @@ -142,7 +147,7 @@ static int freq_inv_set_max_ratio(int cpu, u64 max_rate, u64 ref_rate)
    > > return -EINVAL;
    > > }
    >
    > The return value is no longer used so it might be worth declaring it to
    > return void and WARN_ONCE for unlikely(!max_rate || !ref_rate).
    >
    > >
    > > - per_cpu(arch_max_freq_scale, cpu) = (unsigned long)ratio;
    > > + WRITE_ONCE(per_cpu(arch_max_freq_scale, cpu), (unsigned long)ratio);
    > >
    > > return 0;
    > > }
    > > @@ -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 2372ce791bb4..3a604b77b12d 100644
    > > --- a/drivers/base/arch_topology.c
    > > +++ b/drivers/base/arch_topology.c
    > > @@ -344,6 +344,11 @@ bool __init topology_parse_cpu_capacity(struct device_node *cpu_node, int cpu)
    > > return !ret;
    > > }
    > >
    > > +int __weak freq_inv_set_max_ratio(int cpu, u64 max_rate)
    > > +{
    > > + return 0;
    > > +}
    > > +
    > > #ifdef CONFIG_ACPI_CPPC_LIB
    > > #include <acpi/cppc_acpi.h>
    > >
    > > @@ -369,7 +374,6 @@ void topology_init_cpu_capacity_cppc(void)
    > > capacity_scale = max_t(u64, capacity_scale, raw_capacity[cpu]);
    > >
    > > per_cpu(capacity_ref_freq, cpu) = cppc_perf_to_khz(&perf_caps, raw_capacity[cpu]);
    > > -
    > > pr_debug("cpu_capacity: CPU%d cpu_capacity=%u (raw).\n",
    > > cpu, raw_capacity[cpu]);
    > > continue;
    > > @@ -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));
    > > +
    > > 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));
    >
    > capacity_ref_freq is in KHz while arch_timer_get_rate() is in Hz. One or
    > the other needs to be scaled.
    >
    > The same in topology_init_cpu_capacity_cppc().
    >
    > Thanks,
    > Ionela.
    >
    > > + }
    > >
    > > 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..b6e95d763279 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);
    > > +int freq_inv_set_max_ratio(int cpu, u64 max_rate);
    > > #endif
    > >
    > > #endif /* _LINUX_ARCH_TOPOLOGY_H_ */
    > > --
    > > 2.34.1
    > >

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