Commit 9924fbb5 authored by Ionela Voinescu's avatar Ionela Voinescu Committed by Rafael J. Wysocki
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arch_topology: obtain cpu capacity using information from CPPC 



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: default avatarIonela Voinescu <ionela.voinescu@arm.com>
Acked-by: default avatarSudeep Holla <sudeep.holla@arm.com>
Tested-by: default avatarValentin Schneider <valentin.schneider@arm.com>
Tested-by: default avatarYicong Yang <yangyicong@hisilicon.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 1132e6de

drivers/base/arch_topology.c

+42 −3
Original line number Diff line number Diff line
@@ -339,6 +339,46 @@ 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) &&

		    (perf_caps.highest_perf >= perf_caps.nominal_perf) &&

		    (perf_caps.highest_perf >= perf_caps.lowest_perf)) {

			raw_capacity[cpu] = perf_caps.highest_perf;

			pr_debug("cpu_capacity: CPU%d cpu_capacity=%u (raw).\n",

				 cpu, raw_capacity[cpu]);

			continue;

		}



		pr_err("cpu_capacity: CPU%d missing/invalid 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);
@@ -387,9 +427,8 @@ static int __init register_cpufreq_notifier(void) 
	int ret;



	/*

	 * on ACPI-based systems we need to use the default cpu capacity

	 * until we have the necessary code to parse the cpu capacity, so

	 * skip registering cpufreq notifier.

	 * On ACPI-based systems skip registering cpufreq notifier as cpufreq

	 * information is not needed for cpu capacity initialization.

	 */

	if (!acpi_disabled || !raw_capacity)

		return -EINVAL;

include/linux/arch_topology.h

+4 −0
Original line number Diff line number Diff line
@@ -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);