On Tue, Aug 24, 2021 at 12:57 PM Ionela Voinescu
<ionela.voinescu@xxxxxxx> wrote:
>
> Define topology_init_cpu_capacity_cppc() to use highest performance
> values from _CPC objects to obtain and set maximum capacity information
> for each CPU. acpi_cppc_processor_probe() is a good point at which to
> trigger the initialization of CPU (u-arch) capacity values, as at this
> point the highest performance values can be obtained from each CPU's
> _CPC objects. Architectures can therefore use this functionality
> through arch_init_invariance_cppc().
>
> The performance scale used by CPPC is a unified scale for all CPUs in
> the system. Therefore, by obtaining the raw highest performance values
> from the _CPC objects, and normalizing them on the [0, 1024] capacity
> scale, used by the task scheduler, we obtain the CPU capacity of each
> CPU.
>
> While an ACPI Notify(0x85) could alert about a change in the highest
> performance value, which should in turn retrigger the CPU capacity
> computations, this notification is not currently handled by the ACPI
> processor driver. When supported, a call to arch_init_invariance_cppc()
> would perform the update.
>
> Signed-off-by: Ionela Voinescu <ionela.voinescu@xxxxxxx>
> Tested-by: Valentin Schneider <valentin.schneider@xxxxxxx>
> Cc: Sudeep Holla <sudeep.holla@xxxxxxx>
> ---
> drivers/base/arch_topology.c | 37 +++++++++++++++++++++++++++++++++++
> include/linux/arch_topology.h | 4 ++++
> 2 files changed, 41 insertions(+)
>
> diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
> index 921312a8d957..358e22cd629e 100644
> --- a/drivers/base/arch_topology.c
> +++ b/drivers/base/arch_topology.c
> @@ -306,6 +306,43 @@ bool __init topology_parse_cpu_capacity(struct device_node *cpu_node, int cpu)
> return !ret;
> }
>
> +#ifdef CONFIG_ACPI_CPPC_LIB
> +#include <acpi/cppc_acpi.h>
> +
> +void topology_init_cpu_capacity_cppc(void)
> +{
> + struct cppc_perf_caps perf_caps;
> + int cpu;
> +
> + if (likely(acpi_disabled || !acpi_cpc_valid()))
> + return;
> +
> + raw_capacity = kcalloc(num_possible_cpus(), sizeof(*raw_capacity),
> + GFP_KERNEL);
> + if (!raw_capacity)
> + return;
> +
> + for_each_possible_cpu(cpu) {
> + if (!cppc_get_perf_caps(cpu, &perf_caps)) {
> + raw_capacity[cpu] = perf_caps.highest_perf;
>From experience, I would advise doing some sanity checking on the
per_caps values before using them here.
Also note that highest_perf may not be sustainable, so would using
highest_perf as raw_capacity[] always work as expected?
> + pr_debug("cpu_capacity: CPU%d cpu_capacity=%u (raw).\n",
> + cpu, raw_capacity[cpu]);
> + } else {
> + pr_err("cpu_capacity: CPU%d missing highest performance.\n", cpu);
> + pr_err("cpu_capacity: partial information: fallback to 1024 for all CPUs\n");
> + goto exit;
> + }
> + }
> +
> + topology_normalize_cpu_scale();
> + schedule_work(&update_topology_flags_work);
> + pr_debug("cpu_capacity: cpu_capacity initialization done\n");
> +
> +exit:
> + free_raw_capacity();
> +}
> +#endif
> +
> #ifdef CONFIG_CPU_FREQ
> static cpumask_var_t cpus_to_visit;
> static void parsing_done_workfn(struct work_struct *work);
> diff --git a/include/linux/arch_topology.h b/include/linux/arch_topology.h
> index f180240dc95f..9cf1a17938f0 100644
> --- a/include/linux/arch_topology.h
> +++ b/include/linux/arch_topology.h
> @@ -11,6 +11,10 @@
> void topology_normalize_cpu_scale(void);
> int topology_update_cpu_topology(void);
>
> +#ifdef CONFIG_ACPI_CPPC_LIB
> +void topology_init_cpu_capacity_cppc(void);
> +#endif
> +
> struct device_node;
> bool topology_parse_cpu_capacity(struct device_node *cpu_node, int cpu);
>
> --
> 2.29.2.dirty
>
