246 lines
6.8 KiB
C
246 lines
6.8 KiB
C
/*
|
|
* 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();
|
|
}
|