1/*
  2 * arch/arm/kernel/topology.c
  3 *
  4 * Copyright (C) 2011 Linaro Limited.
  5 * Written by: Vincent Guittot
  6 *
  7 * based on arch/sh/kernel/topology.c
  8 *
  9 * This file is subject to the terms and conditions of the GNU General Public
 10 * License.  See the file "COPYING" in the main directory of this archive
 11 * for more details.
 12 */
 13
 14#include <linux/cpu.h>
 15#include <linux/cpumask.h>
 16#include <linux/export.h>
 17#include <linux/init.h>
 18#include <linux/percpu.h>
 19#include <linux/node.h>
 20#include <linux/nodemask.h>
 21#include <linux/of.h>
 22#include <linux/sched.h>
 23#include <linux/slab.h>
 24
 25#include <asm/cputype.h>
 26#include <asm/topology.h>
 27
 28/*
 29 * cpu power scale management
 30 */
 31
 32/*
 33 * cpu power table
 34 * This per cpu data structure describes the relative capacity of each core.
 35 * On a heteregenous system, cores don't have the same computation capacity
 36 * and we reflect that difference in the cpu_power field so the scheduler can
 37 * take this difference into account during load balance. A per cpu structure
 38 * is preferred because each CPU updates its own cpu_power field during the
 39 * load balance except for idle cores. One idle core is selected to run the
 40 * rebalance_domains for all idle cores and the cpu_power can be updated
 41 * during this sequence.
 42 */
 43static DEFINE_PER_CPU(unsigned long, cpu_scale);
 44
 45unsigned long arch_scale_freq_power(struct sched_domain *sd, int cpu)
 46{
 47	return per_cpu(cpu_scale, cpu);
 48}
 49
 50static void set_power_scale(unsigned int cpu, unsigned long power)
 51{
 52	per_cpu(cpu_scale, cpu) = power;
 53}
 54
 55#ifdef CONFIG_OF
 56struct cpu_efficiency {
 57	const char *compatible;
 58	unsigned long efficiency;
 59};
 60
 61/*
 62 * Table of relative efficiency of each processors
 63 * The efficiency value must fit in 20bit and the final
 64 * cpu_scale value must be in the range
 65 *   0 < cpu_scale < 3*SCHED_POWER_SCALE/2
 66 * in order to return at most 1 when DIV_ROUND_CLOSEST
 67 * is used to compute the capacity of a CPU.
 68 * Processors that are not defined in the table,
 69 * use the default SCHED_POWER_SCALE value for cpu_scale.
 70 */
 71static const struct cpu_efficiency table_efficiency[] = {
 72	{"arm,cortex-a15", 3891},
 73	{"arm,cortex-a7",  2048},
 74	{NULL, },
 75};
 76
 77static unsigned long *__cpu_capacity;
 78#define cpu_capacity(cpu)	__cpu_capacity[cpu]
 79
 80static unsigned long middle_capacity = 1;
 81
 82/*
 83 * Iterate all CPUs' descriptor in DT and compute the efficiency
 84 * (as per table_efficiency). Also calculate a middle efficiency
 85 * as close as possible to  (max{eff_i} - min{eff_i}) / 2
 86 * This is later used to scale the cpu_power field such that an
 87 * 'average' CPU is of middle power. Also see the comments near
 88 * table_efficiency[] and update_cpu_power().
 89 */
 90static void __init parse_dt_topology(void)
 91{
 92	const struct cpu_efficiency *cpu_eff;
 93	struct device_node *cn = NULL;
 94	unsigned long min_capacity = (unsigned long)(-1);
 95	unsigned long max_capacity = 0;
 96	unsigned long capacity = 0;
 97	int alloc_size, cpu = 0;
 98
 99	alloc_size = nr_cpu_ids * sizeof(*__cpu_capacity);
100	__cpu_capacity = kzalloc(alloc_size, GFP_NOWAIT);
101
102	for_each_possible_cpu(cpu) {
103		const u32 *rate;
104		int len;
105
106		/* too early to use cpu->of_node */
107		cn = of_get_cpu_node(cpu, NULL);
108		if (!cn) {
109			pr_err("missing device node for CPU %d\n", cpu);
110			continue;
111		}
112
113		for (cpu_eff = table_efficiency; cpu_eff->compatible; cpu_eff++)
114			if (of_device_is_compatible(cn, cpu_eff->compatible))
115				break;
116
117		if (cpu_eff->compatible == NULL)
118			continue;
119
120		rate = of_get_property(cn, "clock-frequency", &len);
121		if (!rate || len != 4) {
122			pr_err("%s missing clock-frequency property\n",
123				cn->full_name);
124			continue;
125		}
126
127		capacity = ((be32_to_cpup(rate)) >> 20) * cpu_eff->efficiency;
128
129		/* Save min capacity of the system */
130		if (capacity < min_capacity)
131			min_capacity = capacity;
132
133		/* Save max capacity of the system */
134		if (capacity > max_capacity)
135			max_capacity = capacity;
136
137		cpu_capacity(cpu) = capacity;
138	}
139
140	/* If min and max capacities are equals, we bypass the update of the
141	 * cpu_scale because all CPUs have the same capacity. Otherwise, we
142	 * compute a middle_capacity factor that will ensure that the capacity
143	 * of an 'average' CPU of the system will be as close as possible to
144	 * SCHED_POWER_SCALE, which is the default value, but with the
145	 * constraint explained near table_efficiency[].
146	 */
147	if (4*max_capacity < (3*(max_capacity + min_capacity)))
148		middle_capacity = (min_capacity + max_capacity)
149				>> (SCHED_POWER_SHIFT+1);
150	else
151		middle_capacity = ((max_capacity / 3)
152				>> (SCHED_POWER_SHIFT-1)) + 1;
153
154}
155
156/*
157 * Look for a customed capacity of a CPU in the cpu_capacity table during the
158 * boot. The update of all CPUs is in O(n^2) for heteregeneous system but the
159 * function returns directly for SMP system.
160 */
161static void update_cpu_power(unsigned int cpu)
162{
163	if (!cpu_capacity(cpu))
164		return;
165
166	set_power_scale(cpu, cpu_capacity(cpu) / middle_capacity);
167
168	printk(KERN_INFO "CPU%u: update cpu_power %lu\n",
169		cpu, arch_scale_freq_power(NULL, cpu));
170}
171
172#else
173static inline void parse_dt_topology(void) {}
174static inline void update_cpu_power(unsigned int cpuid) {}
175#endif
176
177 /*
178 * cpu topology table
179 */
180struct cputopo_arm cpu_topology[NR_CPUS];
181EXPORT_SYMBOL_GPL(cpu_topology);
182
183const struct cpumask *cpu_coregroup_mask(int cpu)
184{
185	return &cpu_topology[cpu].core_sibling;
186}
187
188static void update_siblings_masks(unsigned int cpuid)
189{
190	struct cputopo_arm *cpu_topo, *cpuid_topo = &cpu_topology[cpuid];
191	int cpu;
192
193	/* update core and thread sibling masks */
194	for_each_possible_cpu(cpu) {
195		cpu_topo = &cpu_topology[cpu];
196
197		if (cpuid_topo->socket_id != cpu_topo->socket_id)
198			continue;
199
200		cpumask_set_cpu(cpuid, &cpu_topo->core_sibling);
201		if (cpu != cpuid)
202			cpumask_set_cpu(cpu, &cpuid_topo->core_sibling);
203
204		if (cpuid_topo->core_id != cpu_topo->core_id)
205			continue;
206
207		cpumask_set_cpu(cpuid, &cpu_topo->thread_sibling);
208		if (cpu != cpuid)
209			cpumask_set_cpu(cpu, &cpuid_topo->thread_sibling);
210	}
211	smp_wmb();
212}
213
214/*
215 * store_cpu_topology is called at boot when only one cpu is running
216 * and with the mutex cpu_hotplug.lock locked, when several cpus have booted,
217 * which prevents simultaneous write access to cpu_topology array
218 */
219void store_cpu_topology(unsigned int cpuid)
220{
221	struct cputopo_arm *cpuid_topo = &cpu_topology[cpuid];
222	unsigned int mpidr;
223
224	/* If the cpu topology has been already set, just return */
225	if (cpuid_topo->core_id != -1)
226		return;
227
228	mpidr = read_cpuid_mpidr();
229
230	/* create cpu topology mapping */
231	if ((mpidr & MPIDR_SMP_BITMASK) == MPIDR_SMP_VALUE) {
232		/*
233		 * This is a multiprocessor system
234		 * multiprocessor format & multiprocessor mode field are set
235		 */
236
237		if (mpidr & MPIDR_MT_BITMASK) {
238			/* core performance interdependency */
239			cpuid_topo->thread_id = MPIDR_AFFINITY_LEVEL(mpidr, 0);
240			cpuid_topo->core_id = MPIDR_AFFINITY_LEVEL(mpidr, 1);
241			cpuid_topo->socket_id = MPIDR_AFFINITY_LEVEL(mpidr, 2);
242		} else {
243			/* largely independent cores */
244			cpuid_topo->thread_id = -1;
245			cpuid_topo->core_id = MPIDR_AFFINITY_LEVEL(mpidr, 0);
246			cpuid_topo->socket_id = MPIDR_AFFINITY_LEVEL(mpidr, 1);
247		}
248	} else {
249		/*
250		 * This is an uniprocessor system
251		 * we are in multiprocessor format but uniprocessor system
252		 * or in the old uniprocessor format
253		 */
254		cpuid_topo->thread_id = -1;
255		cpuid_topo->core_id = 0;
256		cpuid_topo->socket_id = -1;
257	}
258
259	update_siblings_masks(cpuid);
260
261	update_cpu_power(cpuid);
262
263	printk(KERN_INFO "CPU%u: thread %d, cpu %d, socket %d, mpidr %x\n",
264		cpuid, cpu_topology[cpuid].thread_id,
265		cpu_topology[cpuid].core_id,
266		cpu_topology[cpuid].socket_id, mpidr);
267}
268
269/*
270 * init_cpu_topology is called at boot when only one cpu is running
271 * which prevent simultaneous write access to cpu_topology array
272 */
273void __init init_cpu_topology(void)
274{
275	unsigned int cpu;
276
277	/* init core mask and power*/
278	for_each_possible_cpu(cpu) {
279		struct cputopo_arm *cpu_topo = &(cpu_topology[cpu]);
280
281		cpu_topo->thread_id = -1;
282		cpu_topo->core_id =  -1;
283		cpu_topo->socket_id = -1;
284		cpumask_clear(&cpu_topo->core_sibling);
285		cpumask_clear(&cpu_topo->thread_sibling);
286
287		set_power_scale(cpu, SCHED_POWER_SCALE);
288	}
289	smp_wmb();
290
291	parse_dt_topology();
292}