/*
 * arch/arm64/kernel/topology.c
 *
 * Copyright (C) 2011,2013 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/cpu.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/slab.h>

#include <asm/cputype.h>
#include <asm/smp_plat.h>
#include <asm/topology.h>

/*
 * cpu power scale management
 */

/*
 * cpu power 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_power 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_power 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_power can be updated
 * during this sequence.
 */
static DEFINE_PER_CPU(unsigned long, cpu_scale);

unsigned long arch_scale_freq_power(struct sched_domain *sd, int cpu)
{
	return per_cpu(cpu_scale, cpu);
}

static void set_power_scale(unsigned int cpu, unsigned long power)
{
	per_cpu(cpu_scale, cpu) = power;
}

#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_POWER_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_POWER_SCALE value for cpu_scale.
 */
static const struct cpu_efficiency table_efficiency[] = {
	{ "arm,cortex-a57", 3891 },
	{ "arm,cortex-a53", 2048 },
	{ NULL, },
};

static unsigned long *__cpu_capacity;
#define cpu_capacity(cpu)	__cpu_capacity[cpu]

static unsigned long middle_capacity = 1;
static int cluster_id;

static int __init get_cpu_for_node(struct device_node *node)
{
	struct device_node *cpu_node;
	int cpu;

	cpu_node = of_parse_phandle(node, "cpu", 0);
	if (!cpu_node) {
		pr_crit("%s: Unable to parse CPU phandle\n", node->full_name);
		return -1;
	}

	for_each_possible_cpu(cpu) {
		if (of_get_cpu_node(cpu, NULL) == cpu_node)
			return cpu;
	}

	pr_crit("Unable to find CPU node for %s\n", cpu_node->full_name);
	return -1;
}

static void __init parse_core(struct device_node *core, int core_id)
{
	char name[10];
	bool leaf = true;
	int i, cpu;
	struct device_node *t;

	i = 0;
	do {
		snprintf(name, sizeof(name), "thread%d", i);
		t = of_get_child_by_name(core, name);
		if (t) {
			leaf = false;
			cpu = get_cpu_for_node(t);
			if (cpu) {
				pr_info("CPU%d: socket %d core %d thread %d\n",
					cpu, cluster_id, core_id, i);
				cpu_topology[cpu].socket_id = cluster_id;
				cpu_topology[cpu].core_id = core_id;
				cpu_topology[cpu].thread_id = i;
			} else {
				pr_err("%s: Can't get CPU for thread\n",
				       t->full_name);
			}
		}
		i++;
	} while (t);

	cpu = get_cpu_for_node(core);
	if (cpu >= 0) {
		if (!leaf) {
			pr_err("%s: Core has both threads and CPU\n",
			       core->full_name);
			return;
		}

		pr_info("CPU%d: socket %d core %d\n",
			cpu, cluster_id, core_id);
		cpu_topology[cpu].socket_id = cluster_id;
		cpu_topology[cpu].core_id = core_id;
	} else if (leaf) {
		pr_err("%s: Can't get CPU for leaf core\n", core->full_name);
	}
}

static void __init parse_cluster(struct device_node *cluster)
{
	char name[10];
	bool leaf = true;
	bool has_cores = false;
	struct device_node *c;
	int core_id = 0;
	int i;

	/*
	 * First check for child clusters; we currently ignore any
	 * information about the nesting of clusters and present the
	 * scheduler with a flat list of them.
	 */
	i = 0;
	do {
		snprintf(name, sizeof(name), "cluster%d", i);
		c = of_get_child_by_name(cluster, name);
		if (c) {
			parse_cluster(c);
			leaf = false;
		}
		i++;
	} while (c);

	/* Now check for cores */
	i = 0;
	do {
		snprintf(name, sizeof(name), "core%d", i);
		c = of_get_child_by_name(cluster, name);
		if (c) {
			has_cores = true;

			if (leaf)
				parse_core(c, core_id++);
			else
				pr_err("%s: Non-leaf cluster with core %s\n",
				       cluster->full_name, name);
		}
		i++;
	} while (c);

	if (leaf && !has_cores)
		pr_warn("%s: empty cluster\n", cluster->full_name);

	if (leaf)
		cluster_id++;
}

/*
 * 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_power field such that an
 * 'average' CPU is of middle power. Also see the comments near
 * table_efficiency[] and update_cpu_power().
 */
static void __init parse_dt_topology(void)
{
	const struct cpu_efficiency *cpu_eff;
	struct device_node *cn = NULL;
	unsigned long min_capacity = (unsigned long)(-1);
	unsigned long max_capacity = 0;
	unsigned long capacity = 0;
	int alloc_size, cpu;

	alloc_size = nr_cpu_ids * sizeof(*__cpu_capacity);
	__cpu_capacity = kzalloc(alloc_size, GFP_NOWAIT);

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

	/*
	 * If topology is provided as a cpu-map it is essentially a
	 * root cluster.
	 */
	cn = of_find_node_by_name(cn, "cpu-map");
	if (!cn)
		return;
	parse_cluster(cn);

	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;
		}

		/* check if the cpu is marked as "disabled", if so ignore */
		if (!of_device_is_available(cn))
			continue;

		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) {
			pr_warn("%s: Unknown CPU type\n", cn->full_name);
			continue;
		}

		rate = of_get_property(cn, "clock-frequency", &len);
		if (!rate || len != 4) {
			pr_err("%s: Missing clock-frequency property\n",
				cn->full_name);
			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 equal 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_POWER_SCALE, which is the default value, but with the
	 * constraint explained near table_efficiency[].
	 */
	if (min_capacity == max_capacity)
		return;
	else if (4 * max_capacity < (3 * (max_capacity + min_capacity)))
		middle_capacity = (min_capacity + max_capacity)
				>> (SCHED_POWER_SHIFT+1);
	else
		middle_capacity = ((max_capacity / 3)
				>> (SCHED_POWER_SHIFT-1)) + 1;

}

/*
 * Look for a customed capacity of a CPU in the cpu_topo_data 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_power(unsigned int cpu)
{
	if (!cpu_capacity(cpu))
		return;

	set_power_scale(cpu, cpu_capacity(cpu) / middle_capacity);

	pr_info("CPU%u: update cpu_power %lu\n",
		cpu, arch_scale_freq_power(NULL, cpu));
}

#else
static inline void parse_dt_topology(void) {}
static inline void update_cpu_power(unsigned int cpuid) {}
#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;
}

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();
}

void store_cpu_topology(unsigned int cpuid)
{
	struct cputopo_arm *cpuid_topo = &cpu_topology[cpuid];

	/* DT should have been parsed by the time we get here */
	if (cpuid_topo->core_id == -1)
		pr_info("CPU%u: No topology information configured\n", cpuid);
	else
		update_siblings_masks(cpuid);

	update_cpu_power(cpuid);
}


/*
 * cluster_to_logical_mask - return cpu logical mask of CPUs in a cluster
 * @socket_id:		cluster HW identifier
 * @cluster_mask:	the cpumask location to be initialized, modified by the
 *			function only if return value == 0
 *
 * Return:
 *
 * 0 on success
 * -EINVAL if cluster_mask is NULL or there is no record matching socket_id
 */
int cluster_to_logical_mask(unsigned int socket_id, cpumask_t *cluster_mask)
{
	int cpu;

	if (!cluster_mask)
		return -EINVAL;

	for_each_online_cpu(cpu) {
		if (socket_id == topology_physical_package_id(cpu)) {
			cpumask_copy(cluster_mask, topology_core_cpumask(cpu));
			return 0;
		}
	}

	return -EINVAL;
}

/*
 * 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 power*/
	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);

		set_power_scale(cpu, SCHED_POWER_SCALE);
	}
	smp_wmb();

	parse_dt_topology();
}