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/arch_topology.h> |
15 | #include <linux/cpu.h> |
16 | #include <linux/cpufreq.h> |
17 | #include <linux/cpumask.h> |
18 | #include <linux/export.h> |
19 | #include <linux/init.h> |
20 | #include <linux/percpu.h> |
21 | #include <linux/node.h> |
22 | #include <linux/nodemask.h> |
23 | #include <linux/of.h> |
24 | #include <linux/sched.h> |
25 | #include <linux/sched/topology.h> |
26 | #include <linux/slab.h> |
27 | #include <linux/string.h> |
28 | |
29 | #include <asm/cpu.h> |
30 | #include <asm/cputype.h> |
31 | #include <asm/topology.h> |
32 | |
33 | /* |
34 | * cpu capacity scale management |
35 | */ |
36 | |
37 | /* |
38 | * cpu capacity table |
39 | * This per cpu data structure describes the relative capacity of each core. |
40 | * On a heteregenous system, cores don't have the same computation capacity |
41 | * and we reflect that difference in the cpu_capacity field so the scheduler |
42 | * can take this difference into account during load balance. A per cpu |
43 | * structure is preferred because each CPU updates its own cpu_capacity field |
44 | * during the load balance except for idle cores. One idle core is selected |
45 | * to run the rebalance_domains for all idle cores and the cpu_capacity can be |
46 | * updated during this sequence. |
47 | */ |
48 | |
49 | #ifdef CONFIG_OF |
50 | struct cpu_efficiency { |
51 | const char *compatible; |
52 | unsigned long efficiency; |
53 | }; |
54 | |
55 | /* |
56 | * Table of relative efficiency of each processors |
57 | * The efficiency value must fit in 20bit and the final |
58 | * cpu_scale value must be in the range |
59 | * 0 < cpu_scale < 3*SCHED_CAPACITY_SCALE/2 |
60 | * in order to return at most 1 when DIV_ROUND_CLOSEST |
61 | * is used to compute the capacity of a CPU. |
62 | * Processors that are not defined in the table, |
63 | * use the default SCHED_CAPACITY_SCALE value for cpu_scale. |
64 | */ |
65 | static const struct cpu_efficiency table_efficiency[] = { |
66 | {"arm,cortex-a15" , 3891}, |
67 | {"arm,cortex-a7" , 2048}, |
68 | {NULL, }, |
69 | }; |
70 | |
71 | static unsigned long *__cpu_capacity; |
72 | #define cpu_capacity(cpu) __cpu_capacity[cpu] |
73 | |
74 | static unsigned long middle_capacity = 1; |
75 | static bool cap_from_dt = true; |
76 | |
77 | /* |
78 | * Iterate all CPUs' descriptor in DT and compute the efficiency |
79 | * (as per table_efficiency). Also calculate a middle efficiency |
80 | * as close as possible to (max{eff_i} - min{eff_i}) / 2 |
81 | * This is later used to scale the cpu_capacity field such that an |
82 | * 'average' CPU is of middle capacity. Also see the comments near |
83 | * table_efficiency[] and update_cpu_capacity(). |
84 | */ |
85 | static void __init parse_dt_topology(void) |
86 | { |
87 | const struct cpu_efficiency *cpu_eff; |
88 | struct device_node *cn = NULL; |
89 | unsigned long min_capacity = ULONG_MAX; |
90 | unsigned long max_capacity = 0; |
91 | unsigned long capacity = 0; |
92 | int cpu = 0; |
93 | |
94 | __cpu_capacity = kcalloc(n: nr_cpu_ids, size: sizeof(*__cpu_capacity), |
95 | GFP_NOWAIT); |
96 | |
97 | for_each_possible_cpu(cpu) { |
98 | const __be32 *rate; |
99 | int len; |
100 | |
101 | /* too early to use cpu->of_node */ |
102 | cn = of_get_cpu_node(cpu, NULL); |
103 | if (!cn) { |
104 | pr_err("missing device node for CPU %d\n" , cpu); |
105 | continue; |
106 | } |
107 | |
108 | if (topology_parse_cpu_capacity(cpu_node: cn, cpu)) { |
109 | of_node_put(node: cn); |
110 | continue; |
111 | } |
112 | |
113 | cap_from_dt = false; |
114 | |
115 | for (cpu_eff = table_efficiency; cpu_eff->compatible; cpu_eff++) |
116 | if (of_device_is_compatible(device: cn, cpu_eff->compatible)) |
117 | break; |
118 | |
119 | if (cpu_eff->compatible == NULL) |
120 | continue; |
121 | |
122 | rate = of_get_property(node: cn, name: "clock-frequency" , lenp: &len); |
123 | if (!rate || len != 4) { |
124 | pr_err("%pOF missing clock-frequency property\n" , cn); |
125 | continue; |
126 | } |
127 | |
128 | capacity = ((be32_to_cpup(p: rate)) >> 20) * cpu_eff->efficiency; |
129 | |
130 | /* Save min capacity of the system */ |
131 | if (capacity < min_capacity) |
132 | min_capacity = capacity; |
133 | |
134 | /* Save max capacity of the system */ |
135 | if (capacity > max_capacity) |
136 | max_capacity = capacity; |
137 | |
138 | cpu_capacity(cpu) = capacity; |
139 | } |
140 | |
141 | /* If min and max capacities are equals, we bypass the update of the |
142 | * cpu_scale because all CPUs have the same capacity. Otherwise, we |
143 | * compute a middle_capacity factor that will ensure that the capacity |
144 | * of an 'average' CPU of the system will be as close as possible to |
145 | * SCHED_CAPACITY_SCALE, which is the default value, but with the |
146 | * constraint explained near table_efficiency[]. |
147 | */ |
148 | if (4*max_capacity < (3*(max_capacity + min_capacity))) |
149 | middle_capacity = (min_capacity + max_capacity) |
150 | >> (SCHED_CAPACITY_SHIFT+1); |
151 | else |
152 | middle_capacity = ((max_capacity / 3) |
153 | >> (SCHED_CAPACITY_SHIFT-1)) + 1; |
154 | |
155 | if (cap_from_dt) |
156 | topology_normalize_cpu_scale(); |
157 | } |
158 | |
159 | /* |
160 | * Look for a customed capacity of a CPU in the cpu_capacity table during the |
161 | * boot. The update of all CPUs is in O(n^2) for heteregeneous system but the |
162 | * function returns directly for SMP system. |
163 | */ |
164 | static void update_cpu_capacity(unsigned int cpu) |
165 | { |
166 | if (!cpu_capacity(cpu) || cap_from_dt) |
167 | return; |
168 | |
169 | topology_set_cpu_scale(cpu, cpu_capacity(cpu) / middle_capacity); |
170 | |
171 | pr_info("CPU%u: update cpu_capacity %lu\n" , |
172 | cpu, topology_get_cpu_scale(cpu)); |
173 | } |
174 | |
175 | #else |
176 | static inline void parse_dt_topology(void) {} |
177 | static inline void update_cpu_capacity(unsigned int cpuid) {} |
178 | #endif |
179 | |
180 | /* |
181 | * store_cpu_topology is called at boot when only one cpu is running |
182 | * and with the mutex cpu_hotplug.lock locked, when several cpus have booted, |
183 | * which prevents simultaneous write access to cpu_topology array |
184 | */ |
185 | void store_cpu_topology(unsigned int cpuid) |
186 | { |
187 | struct cpu_topology *cpuid_topo = &cpu_topology[cpuid]; |
188 | unsigned int mpidr; |
189 | |
190 | if (cpuid_topo->package_id != -1) |
191 | goto topology_populated; |
192 | |
193 | mpidr = read_cpuid_mpidr(); |
194 | |
195 | /* create cpu topology mapping */ |
196 | if ((mpidr & MPIDR_SMP_BITMASK) == MPIDR_SMP_VALUE) { |
197 | /* |
198 | * This is a multiprocessor system |
199 | * multiprocessor format & multiprocessor mode field are set |
200 | */ |
201 | |
202 | if (mpidr & MPIDR_MT_BITMASK) { |
203 | /* core performance interdependency */ |
204 | cpuid_topo->thread_id = MPIDR_AFFINITY_LEVEL(mpidr, 0); |
205 | cpuid_topo->core_id = MPIDR_AFFINITY_LEVEL(mpidr, 1); |
206 | cpuid_topo->package_id = MPIDR_AFFINITY_LEVEL(mpidr, 2); |
207 | } else { |
208 | /* largely independent cores */ |
209 | cpuid_topo->thread_id = -1; |
210 | cpuid_topo->core_id = MPIDR_AFFINITY_LEVEL(mpidr, 0); |
211 | cpuid_topo->package_id = MPIDR_AFFINITY_LEVEL(mpidr, 1); |
212 | } |
213 | } else { |
214 | /* |
215 | * This is an uniprocessor system |
216 | * we are in multiprocessor format but uniprocessor system |
217 | * or in the old uniprocessor format |
218 | */ |
219 | cpuid_topo->thread_id = -1; |
220 | cpuid_topo->core_id = 0; |
221 | cpuid_topo->package_id = -1; |
222 | } |
223 | |
224 | update_cpu_capacity(cpu: cpuid); |
225 | |
226 | pr_info("CPU%u: thread %d, cpu %d, socket %d, mpidr %x\n" , |
227 | cpuid, cpu_topology[cpuid].thread_id, |
228 | cpu_topology[cpuid].core_id, |
229 | cpu_topology[cpuid].package_id, mpidr); |
230 | |
231 | topology_populated: |
232 | update_siblings_masks(cpuid); |
233 | } |
234 | |
235 | /* |
236 | * init_cpu_topology is called at boot when only one cpu is running |
237 | * which prevent simultaneous write access to cpu_topology array |
238 | */ |
239 | void __init init_cpu_topology(void) |
240 | { |
241 | reset_cpu_topology(); |
242 | smp_wmb(); |
243 | |
244 | parse_dt_topology(); |
245 | } |
246 | |