Release 4.15 arch/arm/kernel/topology.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);

	cn = of_find_node_by_path("/cpus");
	if (!cn) {
		pr_err("No CPU information found in DT\n");
		return;
	}

	for_each_possible_cpu(cpu) {
		const u32 *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();
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
Vincent Guittot
222
72.08%
1
12.50%
Juri Lelli
48
15.58%
2
25.00%
Sudeep KarkadaNagesha
28
9.09%
1
12.50%
Mark Brown
6
1.95%
2
25.00%
Nico Pitre
3
0.97%
1
12.50%
Rob Herring
1
0.32%
1
12.50%
Total
308
100.00%
8
100.00%

/*
 * 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(NULL, cpu));
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
Vincent Guittot
32
68.09%
1
14.29%
Sudeep KarkadaNagesha
7
14.89%
1
14.29%
Juri Lelli
4
8.51%
2
28.57%
Nico Pitre
2
4.26%
1
14.29%
Russell King
1
2.13%
1
14.29%
Mark Brown
1
2.13%
1
14.29%
Total
47
100.00%
7
100.00%

#else


static inline void parse_dt_topology(void) {}
Contributors
Person
Tokens
Prop
Commits
CommitProp
Vincent Guittot
8
100.00%
1
100.00%
Total
8
100.00%
1
100.00%



static inline void update_cpu_capacity(unsigned int cpuid) {}
Contributors
Person
Tokens
Prop
Commits
CommitProp
Vincent Guittot
9
90.00%
1
50.00%
Nico Pitre
1
10.00%
1
50.00%
Total
10
100.00%
2
100.00%

#endif

 /*
 * cpu topology table
 */

struct cputopo_arm cpu_topology[NR_CPUS];

EXPORT_SYMBOL_GPL(cpu_topology);



const struct cpumask *cpu_coregroup_mask(int cpu)
{
	return &cpu_topology[cpu].core_sibling;
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
Vincent Guittot
20
100.00%
1
100.00%
Total
20
100.00%
1
100.00%

/*
 * The current assumption is that we can power gate each core independently.
 * This will be superseded by DT binding once available.
 */


const struct cpumask *cpu_corepower_mask(int cpu)
{
	return &cpu_topology[cpu].thread_sibling;
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
Vincent Guittot
20
100.00%
1
100.00%
Total
20
100.00%
1
100.00%



static void update_siblings_masks(unsigned int cpuid)
{
	struct cputopo_arm *cpu_topo, *cpuid_topo = &cpu_topology[cpuid];
	int cpu;

	/* update core and thread sibling masks */
	for_each_possible_cpu(cpu) {
		cpu_topo = &cpu_topology[cpu];

		if (cpuid_topo->socket_id != cpu_topo->socket_id)
			continue;

		cpumask_set_cpu(cpuid, &cpu_topo->core_sibling);
		if (cpu != cpuid)
			cpumask_set_cpu(cpu, &cpuid_topo->core_sibling);

		if (cpuid_topo->core_id != cpu_topo->core_id)
			continue;

		cpumask_set_cpu(cpuid, &cpu_topo->thread_sibling);
		if (cpu != cpuid)
			cpumask_set_cpu(cpu, &cpuid_topo->thread_sibling);
	}
	smp_wmb();
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
Vincent Guittot
118
99.16%
1
50.00%
Mark Brown
1
0.84%
1
50.00%
Total
119
100.00%
2
100.00%

/*
 * 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 cputopo_arm *cpuid_topo = &cpu_topology[cpuid];
	unsigned int mpidr;

	/* If the cpu topology has been already set, just return */
	if (cpuid_topo->core_id != -1)
		return;

	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->socket_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->socket_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->socket_id = -1;
	}

	update_siblings_masks(cpuid);

	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].socket_id, mpidr);
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
Vincent Guittot
166
86.01%
3
50.00%
Lorenzo Pieralisi
25
12.95%
1
16.67%
Nico Pitre
1
0.52%
1
16.67%
Russell King
1
0.52%
1
16.67%
Total
193
100.00%
6
100.00%



static inline int cpu_corepower_flags(void)
{
	return SD_SHARE_PKG_RESOURCES  | SD_SHARE_POWERDOMAIN;
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
Vincent Guittot
14
100.00%
1
100.00%
Total
14
100.00%
1
100.00%


static struct sched_domain_topology_level arm_topology[] = {
#ifdef CONFIG_SCHED_MC
	{ cpu_corepower_mask, cpu_corepower_flags, SD_INIT_NAME(GMC) },
	{ cpu_coregroup_mask, cpu_core_flags, SD_INIT_NAME(MC) },
#endif
	{ cpu_cpu_mask, SD_INIT_NAME(DIE) },
	{ NULL, },
};

/*
 * 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)
{
	unsigned int cpu;

	/* init core mask and capacity */
	for_each_possible_cpu(cpu) {
		struct cputopo_arm *cpu_topo = &(cpu_topology[cpu]);

		cpu_topo->thread_id = -1;
		cpu_topo->core_id =  -1;
		cpu_topo->socket_id = -1;
		cpumask_clear(&cpu_topo->core_sibling);
		cpumask_clear(&cpu_topo->thread_sibling);
	}
	smp_wmb();

	parse_dt_topology();

	/* Set scheduler topology descriptor */
	set_sched_topology(arm_topology);
}
Contributors
Person
Tokens
Prop
Commits
CommitProp
Vincent Guittot
79
97.53%
3
60.00%
Nico Pitre
1
1.23%
1
20.00%
Venkatraman Sathiyamoorthy
1
1.23%
1
20.00%
Total
81
100.00%
5
100.00%

Overall Contributors
Person
Tokens
Prop
Commits
CommitProp
Vincent Guittot
834
82.33%
5
26.32%
Juri Lelli
72
7.11%
4
21.05%
Sudeep KarkadaNagesha
43
4.24%
1
5.26%
Lorenzo Pieralisi
25
2.47%
1
5.26%
Nico Pitre
12
1.18%
1
5.26%
Mark Brown
12
1.18%
2
10.53%
Arnd Bergmann
8
0.79%
1
5.26%
Ingo Molnar
3
0.30%
1
5.26%
Russell King
2
0.20%
1
5.26%
Rob Herring
1
0.10%
1
5.26%
Venkatraman Sathiyamoorthy
1
0.10%
1
5.26%
Total
1013
100.00%
19
100.00%
Directory: arch/arm/kernel

Information contained on this website is for historical information purposes only and does not indicate or represent copyright ownership.