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- /*
- * arch/arm/kernel/topology.c
- *
- * Copyright (C) 2011 Linaro Limited.
- * Written by: Vincent Guittot
- *
- * based on arch/sh/kernel/topology.c
- *
- * This file is subject to the terms and conditions of the GNU General Public
- * License. See the file "COPYING" in the main directory of this archive
- * for more details.
- */
- #include <linux/arch_topology.h>
- #include <linux/cpu.h>
- #include <linux/cpufreq.h>
- #include <linux/cpumask.h>
- #include <linux/export.h>
- #include <linux/init.h>
- #include <linux/percpu.h>
- #include <linux/node.h>
- #include <linux/nodemask.h>
- #include <linux/of.h>
- #include <linux/sched.h>
- #include <linux/sched/topology.h>
- #include <linux/slab.h>
- #include <linux/string.h>
- #include <asm/cpu.h>
- #include <asm/cputype.h>
- #include <asm/topology.h>
- /*
- * cpu capacity scale management
- */
- /*
- * cpu capacity table
- * This per cpu data structure describes the relative capacity of each core.
- * On a heteregenous system, cores don't have the same computation capacity
- * and we reflect that difference in the cpu_capacity field so the scheduler
- * can take this difference into account during load balance. A per cpu
- * structure is preferred because each CPU updates its own cpu_capacity field
- * during the load balance except for idle cores. One idle core is selected
- * to run the rebalance_domains for all idle cores and the cpu_capacity can be
- * updated during this sequence.
- */
- #ifdef CONFIG_OF
- struct cpu_efficiency {
- const char *compatible;
- unsigned long efficiency;
- };
- /*
- * Table of relative efficiency of each processors
- * The efficiency value must fit in 20bit and the final
- * cpu_scale value must be in the range
- * 0 < cpu_scale < 3*SCHED_CAPACITY_SCALE/2
- * in order to return at most 1 when DIV_ROUND_CLOSEST
- * is used to compute the capacity of a CPU.
- * Processors that are not defined in the table,
- * use the default SCHED_CAPACITY_SCALE value for cpu_scale.
- */
- static const struct cpu_efficiency table_efficiency[] = {
- {"arm,cortex-a15", 3891},
- {"arm,cortex-a7", 2048},
- {NULL, },
- };
- static unsigned long *__cpu_capacity;
- #define cpu_capacity(cpu) __cpu_capacity[cpu]
- static unsigned long middle_capacity = 1;
- static bool cap_from_dt = true;
- /*
- * Iterate all CPUs' descriptor in DT and compute the efficiency
- * (as per table_efficiency). Also calculate a middle efficiency
- * as close as possible to (max{eff_i} - min{eff_i}) / 2
- * This is later used to scale the cpu_capacity field such that an
- * 'average' CPU is of middle capacity. Also see the comments near
- * table_efficiency[] and update_cpu_capacity().
- */
- static void __init parse_dt_topology(void)
- {
- const struct cpu_efficiency *cpu_eff;
- struct device_node *cn = NULL;
- unsigned long min_capacity = ULONG_MAX;
- unsigned long max_capacity = 0;
- unsigned long capacity = 0;
- int cpu = 0;
- __cpu_capacity = kcalloc(nr_cpu_ids, sizeof(*__cpu_capacity),
- GFP_NOWAIT);
- for_each_possible_cpu(cpu) {
- const __be32 *rate;
- int len;
- /* too early to use cpu->of_node */
- cn = of_get_cpu_node(cpu, NULL);
- if (!cn) {
- pr_err("missing device node for CPU %d\n", cpu);
- continue;
- }
- if (topology_parse_cpu_capacity(cn, cpu)) {
- of_node_put(cn);
- continue;
- }
- cap_from_dt = false;
- for (cpu_eff = table_efficiency; cpu_eff->compatible; cpu_eff++)
- if (of_device_is_compatible(cn, cpu_eff->compatible))
- break;
- if (cpu_eff->compatible == NULL)
- continue;
- rate = of_get_property(cn, "clock-frequency", &len);
- if (!rate || len != 4) {
- pr_err("%pOF missing clock-frequency property\n", cn);
- continue;
- }
- capacity = ((be32_to_cpup(rate)) >> 20) * cpu_eff->efficiency;
- /* Save min capacity of the system */
- if (capacity < min_capacity)
- min_capacity = capacity;
- /* Save max capacity of the system */
- if (capacity > max_capacity)
- max_capacity = capacity;
- cpu_capacity(cpu) = capacity;
- }
- /* If min and max capacities are equals, we bypass the update of the
- * cpu_scale because all CPUs have the same capacity. Otherwise, we
- * compute a middle_capacity factor that will ensure that the capacity
- * of an 'average' CPU of the system will be as close as possible to
- * SCHED_CAPACITY_SCALE, which is the default value, but with the
- * constraint explained near table_efficiency[].
- */
- if (4*max_capacity < (3*(max_capacity + min_capacity)))
- middle_capacity = (min_capacity + max_capacity)
- >> (SCHED_CAPACITY_SHIFT+1);
- else
- middle_capacity = ((max_capacity / 3)
- >> (SCHED_CAPACITY_SHIFT-1)) + 1;
- if (cap_from_dt)
- topology_normalize_cpu_scale();
- }
- /*
- * Look for a customed capacity of a CPU in the cpu_capacity table during the
- * boot. The update of all CPUs is in O(n^2) for heteregeneous system but the
- * function returns directly for SMP system.
- */
- static void update_cpu_capacity(unsigned int cpu)
- {
- if (!cpu_capacity(cpu) || cap_from_dt)
- return;
- topology_set_cpu_scale(cpu, cpu_capacity(cpu) / middle_capacity);
- pr_info("CPU%u: update cpu_capacity %lu\n",
- cpu, topology_get_cpu_scale(cpu));
- }
- #else
- static inline void parse_dt_topology(void) {}
- static inline void update_cpu_capacity(unsigned int cpuid) {}
- #endif
- /*
- * store_cpu_topology is called at boot when only one cpu is running
- * and with the mutex cpu_hotplug.lock locked, when several cpus have booted,
- * which prevents simultaneous write access to cpu_topology array
- */
- void store_cpu_topology(unsigned int cpuid)
- {
- struct cpu_topology *cpuid_topo = &cpu_topology[cpuid];
- unsigned int mpidr;
- if (cpuid_topo->package_id != -1)
- goto topology_populated;
- mpidr = read_cpuid_mpidr();
- /* create cpu topology mapping */
- if ((mpidr & MPIDR_SMP_BITMASK) == MPIDR_SMP_VALUE) {
- /*
- * This is a multiprocessor system
- * multiprocessor format & multiprocessor mode field are set
- */
- if (mpidr & MPIDR_MT_BITMASK) {
- /* core performance interdependency */
- cpuid_topo->thread_id = MPIDR_AFFINITY_LEVEL(mpidr, 0);
- cpuid_topo->core_id = MPIDR_AFFINITY_LEVEL(mpidr, 1);
- cpuid_topo->package_id = MPIDR_AFFINITY_LEVEL(mpidr, 2);
- } else {
- /* largely independent cores */
- cpuid_topo->thread_id = -1;
- cpuid_topo->core_id = MPIDR_AFFINITY_LEVEL(mpidr, 0);
- cpuid_topo->package_id = MPIDR_AFFINITY_LEVEL(mpidr, 1);
- }
- } else {
- /*
- * This is an uniprocessor system
- * we are in multiprocessor format but uniprocessor system
- * or in the old uniprocessor format
- */
- cpuid_topo->thread_id = -1;
- cpuid_topo->core_id = 0;
- cpuid_topo->package_id = -1;
- }
- update_cpu_capacity(cpuid);
- pr_info("CPU%u: thread %d, cpu %d, socket %d, mpidr %x\n",
- cpuid, cpu_topology[cpuid].thread_id,
- cpu_topology[cpuid].core_id,
- cpu_topology[cpuid].package_id, mpidr);
- topology_populated:
- update_siblings_masks(cpuid);
- }
- /*
- * init_cpu_topology is called at boot when only one cpu is running
- * which prevent simultaneous write access to cpu_topology array
- */
- void __init init_cpu_topology(void)
- {
- reset_cpu_topology();
- smp_wmb();
- parse_dt_topology();
- }
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